Hyperpolyglot Lisp: Common Lisp, Racket, Clojure, Emacs Lisp
Summary
A side-by-side reference sheet comparing syntax and features of Common Lisp, Racket, Clojure, and Emacs Lisp.
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Cached at: 05/17/26, 05:20 AM
# Lisp: Common Lisp, Racket, Clojure, Emacs Lisp
Source: [https://hyperpolyglot.org/lisp](https://hyperpolyglot.org/lisp)
c*a side\-by\-side reference sheet*
[grammar and execution](https://hyperpolyglot.org/lisp#grammar-execution)\|[variables and expressions](https://hyperpolyglot.org/lisp#var-expr)\|[arithmetic and logic](https://hyperpolyglot.org/lisp#arithmetic-logic)\|[strings](https://hyperpolyglot.org/lisp#strings)\|[regular expressions](https://hyperpolyglot.org/lisp#regexes)\|[dates and time](https://hyperpolyglot.org/lisp#dates-time)\|[lists](https://hyperpolyglot.org/lisp#lists)\|[fixed\-length arrays](https://hyperpolyglot.org/lisp#fixed-length-arrays)\|[dictionaries](https://hyperpolyglot.org/lisp#dictionaries)\|[user\-defined types](https://hyperpolyglot.org/lisp#user-defined-types)\|[functions](https://hyperpolyglot.org/lisp#functions)\|[execution control](https://hyperpolyglot.org/lisp#execution-control)\|[exceptions](https://hyperpolyglot.org/lisp#exceptions)\|[streams](https://hyperpolyglot.org/lisp#streams)\|[emacs buffers](https://hyperpolyglot.org/lisp#emacs-buffers)\|[files](https://hyperpolyglot.org/lisp#files)\|[directories](https://hyperpolyglot.org/lisp#directories)\|[processes and environment](https://hyperpolyglot.org/lisp#processes-environment)\|[libraries and namespaces](https://hyperpolyglot.org/lisp#libraries-namespaces)\|[objects](https://hyperpolyglot.org/lisp#objects)\|[lisp macros](https://hyperpolyglot.org/lisp#lisp-macros)\|[reflection](https://hyperpolyglot.org/lisp#reflection)\|[java interop](https://hyperpolyglot.org/lisp#java-interop)
[common lisp](https://hyperpolyglot.org/lisp#common-lisp)[racket](https://hyperpolyglot.org/lisp#racket)[clojure](https://hyperpolyglot.org/lisp#clojure)[emacs lisp](https://hyperpolyglot.org/lisp#emacs-lisp)[version used](https://hyperpolyglot.org/lisp#version-used-note)
*SBCL 1\.2**Racket 6\.1**Clojure 1\.6**Emacs 24\.5*[show version](https://hyperpolyglot.org/lisp#show-version-note)
$ sbcl\-\-version$ racket\-\-version*displayed by repl on startup*$ emacs\-\-version[grammar and execution](https://hyperpolyglot.org/lisp#grammar-execution-note)common lispracketclojureemacs lisp[compiler](https://hyperpolyglot.org/lisp#compiler-note)
$ raco make*module*\.rktM\-x byte\-compile\-file[standalone executable](https://hyperpolyglot.org/lisp#standalone-executable-note)\(sb\-ext:save\-lisp\-and\-die
"*executable*"
:executable t
:toplevel '*function*\)$ mzc —exe*executable**file*[interpreter](https://hyperpolyglot.org/lisp#interpreter-note)
$ sbcl\-\-script foo\.lisp$ racket \-r foo\.racket*specify full path to clojure jar:*java \-cp clojure\.jar clojure\.main foo\.clj
[shebang](https://hyperpolyglot.org/lisp#shebang-note)\#\!/usr/bin/env sbcl\-\-script\#\!/usr/bin/env racket\-\-script*specify full path to clojure jar:*\#\!/usr/bin/env java \-jar clojure\.jar
\#\!/usr/bin/env emacs\-\-script[repl](https://hyperpolyglot.org/lisp#repl-note)
$ sbcl$ racket$ java \-jar /PATH/TO/clojure\.jarM\-x ielm[command line program](https://hyperpolyglot.org/lisp#cmd-line-program-note)$ racket \-e '\(\+ 1 1\)'[word separator](https://hyperpolyglot.org/lisp#word-separator-note)
*whitespace**whitespace**whitespace and commas**whitespace*[end\-of\-line comment](https://hyperpolyglot.org/lisp#eol-comment-note)\(\+ 1 1\); adding\(\+ 1 1\); adding\(\+ 1 1\); adding\(\+ 1 1\); adding[multiple line comment](https://hyperpolyglot.org/lisp#multiple-line-comment-note)\(\+ 1 \#\| adding \|\# 1\)\(\+ 1 \#\| adding \|\# 1\)[variables and expressions](https://hyperpolyglot.org/lisp#var-expr-note)common lispracketclojureemacs lisp[identifier](https://hyperpolyglot.org/lisp#id-note)*case insensitive, cannot start with digit**excluded characters:* SP \( \) " , '\`: ; \# \| \\
*reserved for user macros:* ? \! \[ \] \{ \}
*case sensitive, cannot start with digit**excluded characters:* SP \( \) \[ \] \{ \} " , '\`; \# \| \\
*case sensitive, cannot start with digit**permitted characters:* A\-Z a\-z 0\-9 \* \+ \! \- \_ ?
*these have special meaning or are reserved:* / \. :
*case sensitive, cannot start with digit**excluded characters:* SP \( \) " , '\`; \# \| \\ \_ \[ \]
[quoted identifier](https://hyperpolyglot.org/lisp#quoted-id-note)
*and escaped identifier*\(setq \|white space symbol\| 3\)\(setq white\\ space\\ symbol 3\)
\(define \|white space symbol\| 3\)\(define white\\ space\\ symbol 3\)
*none**none*
*none*\(setq white\\ space\\ symbol 3\)
[local variable](https://hyperpolyglot.org/lisp#local-var-note); parallel assignment:
\(let \(\(x 3\) \(y 4\)\)
\(\+ x y\)\); sequential assignment: \(let\* \(\(x 3\) \(y \(\* x x\)\)\) \(\+ x y\)\)
; parallel assignment:
\(let \(\(x 3\) \(y 4\)\)
\(\+ x y\)\); sequential assignment: \(let\* \(\(x 3\) \(y \(\* x x\)\)\) \(\+ x y\)\)
\(let \[x 3 y 4\]
\(\+ x y\)\)\(let \[\[x y\] \[3 4\]\] \(\+ x y\)\)
\(let \[x 3 y \(\* x x\)\] \(\+ x y\)\)
; parallel assignment:
\(lexical\-let \(\(x 3\) \(y 4\)\)
\(\+ x y\)\)\(lexical\-let\* \(\(x 3\) \(y \(\* x x\)\)\) \(\+ x y\)\)
[global variable](https://hyperpolyglot.org/lisp#global-var-note)
\(defparameter \*x\* 3\); doesn't change x if already set: \(defvar \*x\* 3\)
\(define x 3\); y is not global: \(define \(double z\) \(define y 2\) \(\* y z\)\)
\(def x 3\)\(set 'x 3\)
\(setq x 3\)[remove variable](https://hyperpolyglot.org/lisp#rm-var-note)
\(makunbound 'x\)\(namespace\-undefine\-variable\! 'x\)\(ns\-unmap \*ns\* 'x\)\(makunbound 'x\)[null](https://hyperpolyglot.org/lisp#null-note)
nil '\(\)null '\(\); same value as null in Java:
nilnil '\(\)[null test](https://hyperpolyglot.org/lisp#null-test-note)
\(null x\)\(null? x\)\(nil? x\)\(null x\)[identifier as value](https://hyperpolyglot.org/lisp#id-as-val-note)'x
\(quote x\)'x
\(quote x\)'x
\(quote x\)'x
\(quote x\)[identifier test](https://hyperpolyglot.org/lisp#id-test-note)
\(symbolp 'x\)\(symbol? 'x\)\(symbol? 'x\)\(symbolp 'x\)identifier equality test\(eq 'x 'x\)\(eq? 'x 'x\)\(= 'x 'x\)\(eq 'x 'x\)[non\-referential identifier](https://hyperpolyglot.org/lisp#non-referential-id-note)
:foo\#:foo:foo:foo[identifier attributes](https://hyperpolyglot.org/lisp#id-attr-note)
*set, get, remove*\(set 'x 13\)\(setf \(get 'x :desc\) "unlucky"\) \(get 'x :desc\) \(remprop 'x :desc\)
*none*; value must be instance of clojure\.lang\.IObj:\(def x \(with\-meta \[13\] \{:desc "unlucky"\}\)\) \(get \(meta x\) :desc\) ; none
\(set 'x 13\)\(setf \(get 'x :desc\) "unlucky"\) \(get 'x :desc\) \(remprop 'x :desc\)
[arithmetic and logic](https://hyperpolyglot.org/lisp#arithmetic-logic-note)common lispracketclojureemacs lisp[true and false](https://hyperpolyglot.org/lisp#true-false-note)t nil\#t \#f
true falsetrue falset nil[falsehoods](https://hyperpolyglot.org/lisp#falsehoods-note)
nil \(\)\#f falsefalse nilnil \(\)[logical operators](https://hyperpolyglot.org/lisp#logical-op-note)
\(or \(not t\) \(and t nil\)\)\(or \(not \#t\) \(and \#t \#f\)\)\(or \(not true\) \(and true false\)\)\(or \(not t\) \(and t nil\)\)[relational operators](https://hyperpolyglot.org/lisp#relational-op-note)
=/= < \> <= \>==*none*< \> <= \>==not= < \> <= \>==/= < \> <= \>=[min and max](https://hyperpolyglot.org/lisp#min-max-note)\(min 1 2 3\)
\(max 1 2 3\)\(min 1 2 3\)
\(max 1 2 3\)\(min 1 2 3\)
\(max 1 2 3\)\(min 1 2 3\)
\(max 1 2 3\)[numeric predicates](https://hyperpolyglot.org/lisp#num-predicates-note)numberp integerp
rationalp floatp
realp complexpnumber? integer?
rational? inexact?
real? complex?number? integer?
rational? float?
*none**none*numberp integerp
*none*floatp
*none**none*[arithmetic operators](https://hyperpolyglot.org/lisp#arith-op-note)
\+ \- \* / mod\+ \- \* / modulo\+ \- \* / mod\+ \- \* / %[integer division](https://hyperpolyglot.org/lisp#int-div-note)
*and remainder*\(truncate 7 3\)
\(rem 7 3\)\(quotient 7 3\)
\(remainder 7 3\)\(quot 7 3\)
\(rem 7 3\)\(/ 7 3\)
\(% 7 3\)[integer division by zero](https://hyperpolyglot.org/lisp#int-div-zero-note)division\-by\-zero*error*division by zero*error*arith\-error[float division](https://hyperpolyglot.org/lisp#float-div-note)*rational:*
\(/ 7 3\)*float:* \(/ 7 \(\* 3 1\.0\)\)
*rational:*
\(/ 7 3\)*float:* \(/ 7 \(float 3\)\)
*rational:*
\(/ 7 3\)*float:* \(/ 7 \(\* 3 1\.0\)\)
*integer quotient:*
\(/ 7 3\)*float:* \(/ 7 \(\* 3 1\.0\)\)
[float division by zero](https://hyperpolyglot.org/lisp#float-div-zero-note)division\-by\-zero*error*\-1\.0e\+INF, \-0\.0e\+NaN,*or*1\.0e\+INF[power](https://hyperpolyglot.org/lisp#power-note)\(expt 2 32\)\(expt 2 32\)*returns float:*
\(Math/pow 2 32\)\(expt 2 32\)[sqrt](https://hyperpolyglot.org/lisp#sqrt-note)
\(sqrt 2\)\(sqrt 2\)\(Math/sqrt 2\)\(sqrt 2\)[sqrt \-1](https://hyperpolyglot.org/lisp#sqrt-negative-one)
\#c\(0\.0 1\.0\)0\+1i*\(Math/sqrt \-1\):*NaN\-0\.0e\+NaN[transcendental functions](https://hyperpolyglot.org/lisp#transcendental-func-note)exp log sin cos tan asin acos atan atanexp log sin cos tan asin acos atan atanMath/exp Math/log Math/sin Math/cos Math/tan Math/asin Math/acos Math/atan Math/atan2exp log sin cos tan asin acos atan atan[float truncation](https://hyperpolyglot.org/lisp#float-truncation-note)*return two values, first is integer:*
truncate round ceiling floor*return floats:*
truncate round ceiling floor*return integers:*
int Math/round
*return floats:*
Math/ceil Math/floortruncate round ceiling floor
fround fceiling ffloor
truncate*returns integer*[absolute value](https://hyperpolyglot.org/lisp#abs-val-note)
*and signum*abs signumabs
*racket:*sgnMath/abs Math/signumabs signum[integer overflow](https://hyperpolyglot.org/lisp#int-overflow-note)
*none; arbitrary\-precision integers**none; arbitrary\-precision integers*clojure\.lang\.Numbers\.throwIntOverflow*exception*[float overflow](https://hyperpolyglot.org/lisp#float-overflow-note)
floating\-point\-overflow*error**not literals:*
\-Infity NaN Infinity[rational construction](https://hyperpolyglot.org/lisp#rational-construction-note)\(/ 3 7\); literal: 3/7
\(/ 3 7\); literal: 3/7
; also rational: 2\.718 \(exp 1\)
\(/ 3 7\); literal: 3/7
[rational decomposition](https://hyperpolyglot.org/lisp#rational-decomposition-note)\(numerator 3/7\)
\(denominator 3/7\)\(numerator 3/7\)
\(denominator 3/7\)\(numerator 3/7\)
\(denominator 3/7\)*none**none*[complex construction](https://hyperpolyglot.org/lisp#complex-construction-note)\#c\(1 2\)1\+2i
\(\+ 1 \+2i\)*none**none*[complex decomposition](https://hyperpolyglot.org/lisp#complex-decomposition-note)\(realpart \#c\(1 2\)\)
\(imagpart \#c\(1 2\)\)
\(phase \#c\(1 2\)\)
\(abs \#c\(1 2\)\)
\(conjugate \#c\(1 2\)\)\(real\-part 1\+2i\)
\(imag\-part 1\+2i\)
\(angle 1\+2i\)
\(magnitude 1\+2i\)
\(conjugate 1\+2i\)*none*
*none**none**none*[random number](https://hyperpolyglot.org/lisp#random-num-note)
*uniform integer, uniform float, normal float*\(random 100\)
\(random 1\.0\)
*none*\(random 100\)
\(random\)
*none*\(def rnd \(java\.util\.Random\.\)\)
\(\.nextInt rnd 100\)
\(\.nextFloat rnd\)
\(\.nextGaussian rnd\)\(random 100\)
*none*
*none*[random seed](https://hyperpolyglot.org/lisp#random-seed-note)\(setq \*random\-state\*
\(sb\-ext:seed\-random\-state 17\)\)\(random\-seed 17\)[bit operators](https://hyperpolyglot.org/lisp#bit-op-note)ash*left shift when 2nd argument positive*logand logior logxor lognotarithmetic\-shift*left shift when 2nd argument positive*bitwise\-and bitwise\-ior bitwise\-xor bitwise\-notbit\-shift\-left bit\-shift\-right bit\-and bit\-or bit\-xor bit\-notlsh*left shift when 2nd argument positive*logand logior logxor lognot[binary, octal, and hex literals](https://hyperpolyglot.org/lisp#binary-octal-hex-literals-note)\#b101010
\#o52
\#x2a\#b101010
\#o52
\#x2a[radix](https://hyperpolyglot.org/lisp#radix-note)
\(format nil "~7r" 42\)[strings](https://hyperpolyglot.org/lisp#strings-note)common lispracketclojureemacs lisp[string test](https://hyperpolyglot.org/lisp#str-test-note)
\(stringp "foo"\)\(string? "foo"\)\(string? "foo"\)\(stringp "foo"\)[string literal](https://hyperpolyglot.org/lisp#str-litera-notel)
"foo bar""foo bar""foo bar""foo bar"[newline in literal](https://hyperpolyglot.org/lisp#newline-in-str-literal-note)
*yes**yes**yes**yes*[literal escapes](https://hyperpolyglot.org/lisp#str-literal-esc-note)\\" \\\\\\t \\n \\r \\" \\\\ \\*ooo*\\u*hhhh*\\b \\t \\n \\f \\r \\" \\\\ \\*ooo*\\u*hhhh*\\b \\t \\n \\f \\r \\" \\\\ \\*ooo*\\u*hhhh*\\x*h*\- \\x*hhhhhh*\\C\-*x*\\M\-*x*[constructor](https://hyperpolyglot.org/lisp#str-ctor-note)
\(string \#\\f \#\\o \#\\o\)\(string ?f ?o ?o\)[format string](https://hyperpolyglot.org/lisp#fmt-str-note)\(format nil "~a: ~a ~,2f" "Foo" 7 13\.457\)\(format "~a ~a ~a" "Foo" 7 13\.457\)\(String/format "%s: %d %\.2f"
\(to\-array \["Foo" 7 13\.457\]\)\)\(format "%s: %d %\.2f" "Foo" 7 13\.457\)[format specifiers](https://hyperpolyglot.org/lisp#fmt-specifiers-note)~aany type, human readable
~sany time, read parseable
~%newline
~~tilde
~ccharacter
~,5f5 digits right of decimal mark
~ddecimal
~xhex
~ooctal
~bbinary~aany type, human readable
~sany time, read parseable
~%newline
~~tilde
~ccharacter~ddecimal ~xhex ~ooctal ~bbinary
[compare strings](https://hyperpolyglot.org/lisp#compare-str-note)\(string= "foo" "bar"\)
\(string< "foo" "bar"\)\(string=? "foo" "bar"\)
\(string<? "foo" "bar"\)\(\.equals "foo" "bar"\)
\(\.compareTo "foo" "bar"\)\(string= "foo" "bar"\)
\(string< "foo" "bar"\)[concatenate](https://hyperpolyglot.org/lisp#str-concat-note)
\(concatenate 'string "foo " "bar " "bar"\)\(string\-append "foo " "bar " "baz"\)\(str "foo " "bar " "baz"\)\(concat "foo " "bar " "baz"\)[replicate](https://hyperpolyglot.org/lisp#str-replicate-note)make\-string 3 :initial\-element \#\\f\)\(make\-string 3 \#\\f\)\(String\. \(into\-array
\(\. Character TYPE\)
\(repeat 3 \\f\)\)\)\(make\-string 3 ?f\)[translate case](https://hyperpolyglot.org/lisp#translate-case-note)\(string\-downcase "FOO"\)
\(string\-upcase "foo"\)\(string\-downcase "FOO"\)
\(string\-upcase "foo"\)\(\.toLowerCase "FOO"\)\(downcase "FOO"\)
\(upcase "foo"\)[capitalize](https://hyperpolyglot.org/lisp#capitalize-note); "Foo Bar":
\(string\-capitalize "foo bar"\); "Foo Bar":
\(capitalize "foo"\)[trim](https://hyperpolyglot.org/lisp#string-trim)\(string\-trim
'\(\#\\space \#\\tab \#\\newline\)
" foo "\)\(require srfi/13/string\)
\(string\-trim\-both " foo "\)\(\.trim " foo "\)*none; see notes for an implementation*[pad](https://hyperpolyglot.org/lisp#pad-note)
*on right, on left*\(format nil "~10a" "foo"\)
\(format nil "~10@a" "foo"\)[number to string](https://hyperpolyglot.org/lisp#num-to-str-note)\(concatenate 'string
"value: "
\(princ\-to\-string 8\)\)\(string\-append
"value: "
\(number\-\>string 8\)\)\(str "Value: " 8\)\(concat
"value: "
\(number\-to\-string 8\)\)[string to number](https://hyperpolyglot.org/lisp#str-to-num-note)\(\+ 7 \(parse\-integer "12"\)\)
\(\+ 73\.9 \(read\-from\-string "\.037"\)\)\(\+ 7 \(string\-\>number "12"\)\)
\(\+ 73\.9 \(string\-\>number "\.037"\)\)\(\+ 7 \(Integer/parseInt "12"\)\)
\(\+ 73\.9 \(Float/parseFloat "\.037"\)\)\(\+ 7 \(string\-to\-number "12"\)\)
\(\+ 73\.9 \(string\-to\-number "\.037"\)\)[split](https://hyperpolyglot.org/lisp#split-note)\(cl\-ppcre:split
"\[ \\t\\n\]\+"
"foo bar baz"\)\(regexp\-split \#rx"\[ \\n\\t\]\+"
"foo bar baz"\)\(seq
\(\.split "foo bar baz"
"\[ \\t\\n\]\+"\)\)\(split\-string "foo bar baz"\)[string join](https://hyperpolyglot.org/lisp#str-join-note)\(reduce
\(lambda \(m o\)
\(concatenate 'string m " " o\)\)
'\("foo" "bar" "baz"\)\)\(string\-join
'\("foo" "bar" "baz"\)
" "\)\(reduce \#\(str %1 " " %2\)
'\("foo" "bar" "baz"\)\)\(reduce
\(lambda \(m o\) \(concat m " " o\)\)
'\("foo" "bar" "baz"\)\)[length](https://hyperpolyglot.org/lisp#str-len-note)
\(length "foo"\)\(string\-length "foo"\)\(\.length "foo"\)\(length "foo"\)[index of substring](https://hyperpolyglot.org/lisp#index-substr-note)\(search "bar" "foo bar"\)*racket:*
\(require srfi/13/string\)
\(string\-contains "foo bar" "bar"\)\(\.indexOf "foo bar" "bar"\)\(search "bar" "foo bar"\)[extract substring](https://hyperpolyglot.org/lisp#extract-substr-note)
\(subseq "foo bar" 4 7\)\(substring "foo bar" 4 7\)\(\.substring "foo bar" 4 7\)\(substring "foo bar" 4 7\)[character literal](https://hyperpolyglot.org/lisp#char-literal-note)\#\\a \#\\space \#\\newline \#\\backspace \#\\tab \#\\linefeed \#\\page \#\\return \#\\rubout\#\\a \#\\space \#\\newline \#\\backspace \#\\tab \#\\linefeed \#\\page \#\\return \#\\nul \#\\vtab \#\\alarm \#\\esc \#\\delete
*not in racket:*\#\\alarm \#\\esc \#\\delete\\a \\newline \\space \\backspace \\tab*?*\\formfeed \\return*?*?a ?\\b ?\\t ?\\n ?\\f ?\\r ?\\" ?\\\\ ?\\*ooo*?\\u*hhhh*?\\x*h*\- ?\\x*hhhhhh*?\\C\-*x*?\\M\-*x*[test characters](https://hyperpolyglot.org/lisp#char-test-note)
\(characterp \#\\x\)
\(alpha\-char\-p \#\\x\)
\(alphanumericp \#\\x\)
\(digit\-char\-p \#\\7\)
\(lower\-case\-p \#\\x\)
\(upper\-case\-p \#\\X\)\(char? \#\\x\)\(char? \\x\)\(characterp ?x\)[chr and ord](https://hyperpolyglot.org/lisp#chr-ord-note)\(code\-char 97\)
\(char\-code \#\\a\)\(integer\-\>char 97\)
\(char\-\>integer \#\\a\)\(char 97\)
\(int \\a\)[to array of characters](https://hyperpolyglot.org/lisp#str-to-char-array-note); list:
\(string\-\>list "foo"\)[character lookup](https://hyperpolyglot.org/lisp#lookup-char-note)
\(char "foo" 0\)\(string\-ref "foo" 0\)\(\.charAt "foo" 0\)\(aref "foo" 0\)[regular expressions](https://hyperpolyglot.org/lisp#regexes-note)common lispracketclojureemacs lisp[literal](https://hyperpolyglot.org/lisp#regex-literal-note)*use a string:*
"\\\\b\\\\d\{5\}\\\\b"*posix extended:*
\#rx"^\[0\-9\]\[0\-9\]\[0\-9\]\[0\-9\]\[0\-9\]$"
\(regexp "^\[0\-9\]\[0\-9\]\[0\-9\]\[0\-9\]\[0\-9\]$"\)*perl style:* \#px"\\\\b\\\\d\{5\}\\\\b" \(pregexp "\\\\b\\\\d\{5\}\\\\b"\)
\#"\\b\\d\{5\}\\b"[character class abbrevations](https://hyperpolyglot.org/lisp#char-class-abbrev-note)\. \\d \\D \\s \\S \\w \\W*regexp:*
\.*pregexp:* \. \\d \\D \\s \\S \\w \\W
\. \\d \\D \\s \\S \\w \\W\. \\w \\W \\ca \\cl \\cg \\Ca \\Cl \\Cg \\s*x*\\ca \\cl*and*\\cg*match ASCII, Latin, and Greek characters\.*
*Character classes of the form*\\sx*depend on the current syntax table\.*
[anchors](https://hyperpolyglot.org/lisp#regex-anchors-note)^ $ \\b \\B*regexp:*
^ $*pregexp:* ^ $ \\b \\B
^ $ \\A \\b \\B \\G \\z \\Z^ $ \\b \\B[match test](https://hyperpolyglot.org/lisp#regex-test-note)\(ql:quickload "cl\-ppcre"\)\(if \(cl\-ppcre:all\-matches "1999" s\) \(format t "party\!"\)\)
\(regexp\-match \#rx"bar" "foo bar"\)\(re\-find \#"bar" "foo bar"\)\(string\-match "bar" "foo bar"\)[case insensitive match test](https://hyperpolyglot.org/lisp#case-insensitive-regex-note)\(regexp\-match \#px"\(?i:lorem\)" "Lorem"\)\(re\-find \#"\(?i:lorem\)" "Lorem"\)[substitution](https://hyperpolyglot.org/lisp#subst-note)\(cl\-ppcre:regex\-replace "\[^l\]l"
"hello"
"EL"\)
\(cl\-ppcre:regex\-replace\-all "\[^l\]l"
"hello hello"
"EL"\)\(regexp\-replace \#rx"el"
"hello"
"EL"\)
\(regexp\-replace\* \#rx"el"
"hello hello"
"EL"\)\(\.replaceFirst "hello" "\[^l\]l" "XX"\)
\(\.replaceAll "hello hello"
"\[^l\]l" "XX"\)*?*
\(replace\-regexp\-in\-string "\[^l\]l"
"EL"
"hello hello"\)[group capture](https://hyperpolyglot.org/lisp#group-capture-note)\(match \(regexp\-match
\#px"\(\\\\d\{4\}\)\-\(\\\\d\{2\}\)\-\(\\\\d\{2\}\)"
"2010\-06\-03"\)
\[\(list s yr mn dy\) \(list yr mn dy\)\]\)\(let \[\[\_ yr mn dy\]
\(re\-find \#"\(\\d\{4\}\)\-\(\\d\{2\}\)\-\(\\d\{2\}\)"
"2010\-06\-03"\)\]
yr\)[scan](https://hyperpolyglot.org/lisp#scan-note)\(re\-seq \#"\\w\+" "dolor sit amet"\)[backreference in match and substitution](https://hyperpolyglot.org/lisp#backreference-note)\(regexp\-match \#px"\(\\\\w\+\) \\\\1" "do do"\)\(regexp\-replace \#px"\(\\\\w\+\) \(\\\\w\+\)" "do re" "\\\\2 \\\\1"\)
[dates and time](https://hyperpolyglot.org/lisp#dates-time-note)common lispracketclojureemacs lisp[broken\-down datetime type](https://hyperpolyglot.org/lisp#broken-down-datetime-type-note)*No dedicated type; a list of 9 values is used:*second: 0\-59 minute: 0\-59 hour: 0\-23 day of month: 1\-31 month: 1\-12 year: 4 digits day of week: 0\-6 for Mon\-Sun is daylight savings time: t or nil timezone: negated UTC offset in hours
[current datetime](https://hyperpolyglot.org/lisp#current-datetime-note)\(get\-decoded\-time\)\(require racket/date\)\(current\-date\)
\(def dt \(new java\.util\.Date\)\)\(current\-time\)[current unix epoch](https://hyperpolyglot.org/lisp#current-unix-epoch-note)gray\|; seconds since Jan 1, 1900:\#\#
\(get\-universal\-time\)\(current\-seconds\)\(/ \(System/currentTimeMillis\) 1000\.0\)\(float\-time\)[unix epoch to broken\-down datetime](https://hyperpolyglot.org/lisp#unix-epoch-to-broken-down-datetime-note)\(decode\-universal\-time
\(get\-unversal\-time\)\)\(seconds\-\>date \(current\-seconds\)\)\(def dt \(new java\.util\.Date
\(System/currentTimeMillis\)\)\)\(seconds\-to\-time \(float\-time\)\)[broken\-down datetime to unix epoch](https://hyperpolyglot.org/lisp#broken-down-datetime-to-unix-epoch-note)\(encode\-universal\-time 0 22 10 31 5 2015\)\(require racket/date\)\(date\-\>seconds \(current\-date\)\)
\(/ \(\.getTime \(new java\.util\.Date\)\) 1000\.0\)\(multiple\-value\-bind \(b s\)
\(current\-time\)
\(\+ \(\* b \(expt 2 16\)\) s\)\)[format datetime](https://hyperpolyglot.org/lisp#fmt-datetime-note)\(def s "yyyy\-MM\-dd HH:mm:ss"\)
\(def fmt \(new java\.text\.SimpleDateFormat s\)\)\(\.format fmt \(new java\.util\.Date\)\)
\(format\-time\-string
"%Y\-%m\-%d %H:%M:%S"
\(current\-time\)\)[parse datetime](https://hyperpolyglot.org/lisp#parse-datetime-note)\(require \(prefix\-in s19\. srfi/19\)\)\(define \(date\-str\-\>unix\-time s fmt\) \(s19\.time\-second \(s19\.date\-\>time\-utc \(s19\.string\-\>date s fmt\)\)\)\)
\(date\-str\-\>unix\-time "2015\-05\-31 07:06:00" "~Y\-~m\-~d ~H:~M:~S"\)
\(def s "yyyy\-MM\-dd HH:mm:ss"\)
\(def fmt \(new java\.text\.SimpleDateFormat s\)\)\(\.parse fmt "2015\-05\-30 09:14:14"\)
[date parts](https://hyperpolyglot.org/lisp#date-parts-note)\(multiple\-value\-bind
\(ss mi hr dy mo yr\)
\(get\-decoded\-time\)
\(list ss mi hr\); quiesce warning
\(list dy mo yr\)\)\(date\-year \(current\-date\)\)
\(date\-month \(current\-date\)\)
\(date\-day \(current\-date\)\)\(def cal \(new java\.util\.GregorianCalendar\)\)
\(\.setTime cal dt\)\(\.get cal java\.util\.Calendar/DAY\_OF\_MONTH\) \(\+ \(\.get cal java\.util\.Calendar/MONTH\) 1\) \(\.get cal java\.util\.Calendar/YEAR\)
\(multiple\-value\-bind
\(ss mi hr dy mo yr\)
\(decode\-time \(current\-time\)\)
\(list dy mo yr\)\)[time parts](https://hyperpolyglot.org/lisp#time-parts-note)\(multiple\-value\-bind
\(ss mi hr\)
\(get\-decoded\-time\)
\(list ss mi hr\)\)\(date\-hour \(current\-date\)\)
\(date\-minute \(current\-date\)\)
\(date\-second \(current\-date\)\)\(def cal \(new java\.util\.GregorianCalendar\)\)
\(\.setTime cal dt\)\(\.get cal java\.util\.Calendar/HOUR\_OF\_DAY\) \(\.get cal java\.util\.Calendar/MINUTE\) \(\.get cal java\.util\.Calendar/SECOND\)
\(multiple\-value\-bind
\(ss mi hr dy mo yr\)
\(decode\-time \(current\-time\)\)
\(list ss mi hr\)\)[build broken\-down datetime](https://hyperpolyglot.org/lisp#build-datetime-note)\(encode\-universal\-time 0 22 10 31 5 2015\)\(let
\[yr 2015 mo 5 dy 31 hr 10 mi 22 ss 0\]
\(def cal
\(new java\.util\.GregorianCalendar
yr \(\- mo 1\) dy hr mi ss\)\)\)\(encode\-time 0 50 8 31 5 2015\)[lists](https://hyperpolyglot.org/lisp#lists-note)common lispracketclojureemacs lisp[literal](https://hyperpolyglot.org/lisp#list-literal)
'\(1 2 3\)
\(quote \(1 2 3\)\)'\(1 2 3\)
'\[1 2 3\]
'\{1 2 3\}
\(quote \(1 2 3\)\)'\(1 2 3\)
\(quote \(1 2 3\)\)'\(1 2 3\)
\(quote \(1 2 3\)\)constructor
\(list 1 2 3\)\(list 1 2 3\)\(list 1 2 3\)\(list 1 2 3\)predicate
\(listp '\(1 2 3\)\)\(list? '\(1 2 3\)\)\(list? '\(1 2 3\)\)\(listp '\(1 2 3\)\)empty testnil*and*'\(\)*are synonyms and evaluate as false in a boolean context\. All other values are true\.*\(empty? '\(\)\)\(empty? \(\)\)nil*and*'\(\)*are synonyms and evaluate as false in a boolean context\. All other values are true\.*evaluating the empty listnil*error*\(\)nil[cons](https://hyperpolyglot.org/lisp#cons)
\(cons 1 '\(2 3\)\)\(cons 1 '\(2 3\)\)\(cons 1 '\(2 3\)\)\(cons 1 '\(2 3\)\)head
\(car '\(1 2 3\)\)
\(first '\(1 2 3\)\)\(car '\(1 2 3\)\)
\(first '\(1 2 3\)\)firstcartail
\(cdr '\(1 2 3\)\)
\(rest '\(1 2 3\)\)\(cdr '\(1 2 3\)\)
\(rest '\(1 2 3\)\)\(rest '\(1 2 3\)\)
\(next '\(1 2 3\)\)\(cdr '\(1 2 3\)\)
\(rest '\(1 2 3\)\)head and tail of empty list*both evaluate to*nil*error*\(\)*both evaluate to*nillength
\(length '\(1 2 3\)\)\(length '\(1 2 3\)\)\(count '\(1 2 3\)\)\(length '\(1 2 3\)\)equality test
\(equal '\(1 2 3\) '\(1 2 3\)\)\(equal? '\(1 2 3\) '\(1 2 3\)\)\(= '\(1 2 3\) '\(1 2 3\)\)\(equal '\(1 2 3\) '\(1 2 3\)\)nth element; indexed from zero:
\(nth 2 '\(1 2 3 4\)\)\(list\-ref '\(1 2 3 4\) 2\)\(nth '\(1 2 3 4\) 2\)\(nth 2 '\(1 2 3 4\)\)out\-of\-bounds behaviornil*error**raises*IndexOutOfBoundsExceptionnilelement index\(position 7 '\(5 6 7 8\)\)\(require srfi/1\)\(list\-index \(lambda \(x\) \(= x 7\)\) '\(5 6 7 8\)\)
*none*\(position 7 '\(5 6 7 8\)\)concatenate
\(append '\(1 2 3\) '\(4 5 6\)\)\(append '\(1 2 3\) '\(4 5 6\)\)\(concat '\(1 2 3\) '\(4 5 6\)\)\(append '\(1 2 3\) '\(4 5 6\)\)[take](https://hyperpolyglot.org/lisp#take)
*none*\(take '\(1 2 3 4\) 2\)\(take 2 '\(1 2 3 4\)\)\(subseq '\(1 2 3 4\) 0 2\)[drop](https://hyperpolyglot.org/lisp#drop)
\(nthcdr 2 '\(1 2 3 4\)\)\(drop '\(1 2 3 4\) 2\)\(drop 2 '\(1 2 3 4\)\)\(nthcdr 2 '\(1 2 3 4\)\)last element
\(car \(last '\(1 2 3\)\)\)\(last '\(1 2 3\)\)\(last '\(1 2 3\)\)\(car \(last '\(1 2 3\)\)\)all but last element\(butlast '\(1 2 3\)\)\(define a '\(1 2 3\)\)
\(take a \(\- \(length a\) 1\)\)\(butlast '\(1 2 3\)\)\(butlast '\(1 2 3\)\)reverse
\(reverse '\(1 2 3\)\)\(reverse '\(1 2 3\)\)\(reverse '\(1 2 3\)\)\(reverse '\(1 2 3\)\)[sort](https://hyperpolyglot.org/lisp#sort)
\(sort '\(3 2 4 1\) '<\)\(sort '\(3 2 4 1\) <\)\(sort < '\(3 2 4 1\)\)\(sort '\(3 2 4 1\) '<\)dedupe
\(remove\-duplicates '\(1 1 2 3\)\)\(remove\-duplicates '\(1 1 2 3\)\)\(remove\-duplicates '\(1 1 2 3\)\)membership
\(member 7 '\(1 2 3\)\)\(member 7 '\(1 2 3\)\)\(member 7 '\(1 2 3\)[map](https://hyperpolyglot.org/lisp#map)\(mapcar
\(lambda \(x\) \(\* x x\)\)
'\(1 2 3\)\)\(map \(lambda \(x\) \(\* x x\)\) '\(1 2 3\)\)\(map \#\(\* % %\) '\(1 2 3\)\)\(mapcar
\(lambda \(x\) \(\* x x\)\)
'\(1 2 3\)\)[filter](https://hyperpolyglot.org/lisp#filter)\(remove\-if\-not
\(lambda \(x\) \(\> x 2\)\)
'\(1 2 3\)\); remove\-if returns complement
\(filter
\(lambda \(x\) \(\> x 2\)\)
'\(1 2 3\)\); filter\-not returns complement
\(filter \#\(\> % 2\) '\(1 2 3\)\); remove returns complement
\(remove\-if\-not
\(lambda \(x\) \(\> x 2\)\)
'\(1 2 3\)\); remove\-if returns complement
[reduce](https://hyperpolyglot.org/lisp#reduce)\(reduce '\-
'\(1 2 3 4\)
:initial\-value 0\)\(foldl \(lambda \(x y\) \(\- y x\)\) 0 '\(1 2 3 4\)\)\(reduce \- 0 '\(1 2 3 4\)\)\(reduce '\-
'\(1 2 3 4\)
:initial\-value 0\)[right fold](https://hyperpolyglot.org/lisp#right-fold)\(reduce '\-
'\(1 2 3 4\)
:initial\-value 0
:from\-end t\)\(foldr \- 0 '\(1 2 3 4\)\)*none*\(reduce '\-
'\(1 2 3 4\)
:initial\-value 0
:from\-end t\)iterate\(dolist \(x '\(1 2 3\)\)
\(print x\)
\(print \(\- x\)\)\)\(for \(\(x '\(1 2 3\)\)\)
\(printf "~a~n" x\)
\(printf "~a~n" \(\- x\)\)\)\(doseq \[x '\(1 2 3\)\]
\(println x\)
\(println \(\- x\)\)\)\(dolist \(x '\(1 2 3\)\)
\(print x\)
\(print \(\- x\)\)\)[universal predicate](https://hyperpolyglot.org/lisp#universal-predicate)\(every
\(lambda \(i\) \(= 0 \(rem i 2\)\)\)
'\(1 2 3 4\)\)\(for/and \(\(i '\(1 2 3 4\)\)\)
\(= 0 \(remainder i 2\)\)\)\(every? \#\(= 0 \(rem % 2\)\) '\(1 2 3 4\)\)\(every
\(lambda \(i\) \(= 0 \(% i 2\)\)\)
'\(1 2 3 4\)\)[existential predicate](https://hyperpolyglot.org/lisp#existential-predicate)\(some
\(lambda \(i\) \(= 0 \(rem i 2\)\)\)
'\(1 2 3 4\)\)\(for/or \(\(i '\(1 2 3 4\)\)\)
\(= 0 \(remainder i 2\)\)\)\(some \#\(= 0 \(rem % 2\)\) '\(1 2 3 4\)\)\(some
\(lambda \(i\) \(= 0 \(% i 2\)\)\)
'\(1 2 3 4\)\)list comprehension\(for\*/list
\(\(file "ABCDEFGH"\) \(rank \(in\-range 1 9\)\)\)
\(format "~a~a" file rank\)\)\(for
\[file "ABCDEFGH" rank \(range 1 9\)\]
\(format "%c%d" file rank\)\)shuffle
\(shuffle '\(1 2 3 4\)\)\(shuffle '\(1 2 3 4\)\)set head\(defparameter \*a\* '\(1 2 3\)\)
\(setf \(car \*a\*\) 3\)\(require schema/mpair\)\(define a \(mlist 1 2 3\)\) \(set\-mcar\! a 3\)
*none*\(setq a '\(1 2 3\)
\(setcar a 3\)set tail\(defparameter \*a\* '\(1 2 3\)\)
\(setf \(cdr \*a\*\) '\(4 5 6\)\)\(require schema/mpair\)\(define a \(mlist 1 2 3\)\) \(set\-mcdr\! a \(mlist 4 5 6\)\)
*none*\(setq a '\(1 2 3\)
\(setcar a 3\)
\(setcdr a '\(4 5 6\)\)manipulate back\(defparameter \*a\* '\(1 2 3\)\)
\(push 4 \*a\*\)
\(pop \*a\*\)*none*\(setq a '\(1 2 3\)\)
\(push 4 a\)
\(pop a\)flatten\(flatten '\(1 2 \(3 \(4\)\)\)\)\(flatten '\(1 2 \(3 \(4\)\)\)\)associative array lookup
\(assoc 3 '\(\(1 2\) \(3 4\)\)\)\(assoc 3 '\(\(1 2\) \(3 4\)\)\)*none, see note*\(assoc 3 '\(\(1 2\) \(3 4\)\)\)flat associative array lookup
\(getf '\(1 2 3 4\) 3\)*none**none*\(getf '\(1 2 3 4\) 3\)[pair literal](https://hyperpolyglot.org/lisp#pair-literal)
'\(1 \. 2\)'\(1 \. 2\)*none*'\(1 \. 2\)cons cell test\(cons '\(1 \. 2\)\)
\(not \(atom '\(1 \. 2\)\)\)\(cons? '\(1 \. 2\)\)
\(pair? '\(1 \. 2\)\)*none*\(cons '\(1 \. 2\)\)
\(not \(atom '\(1 \. 2\)\)\)translate elements recursively\(sublis '\(\(1 \. 2\) \(3 \. 4\)\)
'\(1 \(3 3 \(1\)\)\)\)\(sublis '\(\(1 \. 2\) \(3 \. 4\)\)
'\(1 \(3 3 \(1\)\)\)\)[fixed\-length arrays](https://hyperpolyglot.org/lisp#fixed-length-arrays-note)common lispracketclojureemacs lisp[literal](https://hyperpolyglot.org/lisp#fixed-len-array-literal-note)
\#\(1 2 3\)\#\(1 2 3\)\[1 2 3\]\[1 2 3\]constructor
\(vector 1 2 3\)\(vector 1 2 3\)\(vector 1 2 3\)\(vector 1 2 3\)size
\(length \#\(1 2 3\)\)\(vector\-length \#\(1 2 3\)\)\(count \[1 2 3\]\)\(length \[1 2 3\]\)lookup\(elt \#\(1 2 3\) 0\)*or*
\(aref \#\(1 2 3\) 0\)\(vector\-ref \#\(1 2 3\) 0\)\(nth \[1 2 3\] 0\)\(elt \[1 2 3\] 0\)update\(setq v \[1 2 3\]\)
\(setf \(aref v 2\) 4\)\(define v \(vector 1 2 3\)\)
\(vector\-set\! v 2 4\)\(replace \{2 4\} \[1 2 3\]\)\(setq v \#\(1 2 3\)\)
\(setf \(aref v 2\) 4\)out\-of\-bounds behavior*raises*sb\-kernel:index\-too\-large\-error*error*array to list
\(coerce \#\(1 2 3\) 'list\)\(vector\-\>list \#\(1 2 3\)\)\(seq \[1 2 3\]\)\(coerce \[1 2 3\] 'list\)list to array
\(coerce '\(1 2 3\) 'vector\)\(list\-\>vector '\(1 2 3\)\)\(vec '\(1 2 3\)\)\(coerce '\(1 2 3\) 'vector\)reverse\(reverse \#\(1 2 3\)\)sort\(sort \#\(2 4 1 3\) \#'<\)map\(map 'vector \(lambda \(x\) \(\* x x\)\) \#\(1 2 3\)\)filter\(remove\-if\-not \(lambda \(x\) \(\> x 2\)\) \#\(1 2 3\)\); also remove\-if
reduce[dictionaries](https://hyperpolyglot.org/lisp#dictionaries-note)common lispracketclojureemacs lisp[literal](https://hyperpolyglot.org/lisp#dict-literal-note)
*none*; immutable:
\#hash\(\("t" \. 1\) \("f" \. 0\)\); clojure\.lang\.PersistentArrayMap:
\{"t" 1 "f" 0\}*none*[constructor](https://hyperpolyglot.org/lisp#dict-ctor-note)\(defparameter \*h\* \(make\-hash\-table :test 'equal\)\); default equality test is 'eql
\(define ih
\(make\-immutable\-hash
'\(\("t" \. 1\) \("f" \. 0\)\)\)\); mutable: \(define h \(make\-hash '\(\("t" \. 1\) \("f" \. 0\)\)\)\)
; immutable:
\(def ih \(hash\-map "t" 1 "f" 0\)\)\(setq h \(make\-hash\-table :test 'equal\)\)[predicate](https://hyperpolyglot.org/lisp#dict-pred-note)
\(hash\-table\-p \*h\*\)\(hash? h\); also true of assoc\. lists and vectors: \(dict? h\)
\(map? ih\)\(hash\-table\-p h\)[size](https://hyperpolyglot.org/lisp#dict-size-note)
\(hash\-table\-count \*h\*\)\(hash\-count h\); also works with assoc lists and vectors: \(dict\-count ih\)
\(count ih\)\(hash\-table\-count h\)[lookup](https://hyperpolyglot.org/lisp#dict-lookup-note)
\(gethash "t" \*h\*\)\(hash\-ref h "t"\); return \-1 if not found: \(hash\-ref h "m" \-1\)
; also works with assoc\. lists and vectors: \(dict\-ref ih "t"\) \(dict\-ref ih "m" \-1\)
\(get ih "t"\)
\(find ih "t"\); return \-1 if not found: \(get ih "m" \-1\)
\(gethash "t" h\)[update](https://hyperpolyglot.org/lisp#dict-update-note)\(setf \(gethash "t" \*h\*\) 1\)\(hash\-set\! h "t" 2\)\(define ih2 \(hash\-set ih "t" 2\)\)
; also dict\-set\! and dict\-set
\(def ih2 \(assoc ih "t" 2\)\)\(puthash "t" 1 h\)[missing key behavior](https://hyperpolyglot.org/lisp#dict-missing-key-note)*returns*nil*error**returns*nil*returns*nil[is key present](https://hyperpolyglot.org/lisp#dict-is-key-present-note)
\(nth\-value 1 \(gethash "t" \*h\*\)\)\(hash\-has\-key? h "t"\); also dict\-has\-key?
\(contains? ih "t"\)*none*[delete](https://hyperpolyglot.org/lisp#dict-del-note)\(remhash "t" \*h\*\)\(hash\-remove\! h "t"\)
\(define ih2
\(hash\-remove ih "t"\)\); also dict\-remove\! and dict\-remove
\(def ih2 \(dissoc ih "t"\)\)\(remhash "hello" h\)[merge](https://hyperpolyglot.org/lisp#dict-merge-note); values in ih2 take precedence:
\(define ih3 \(merge ih ih2\)\)[invert](https://hyperpolyglot.org/lisp#dict-invert-note)\(require 'clojure\.set\)\(define ih4 \(clojure\.set/map\-invert ih\)\)
[iterate](https://hyperpolyglot.org/lisp#dict-iter-note)\(maphash
\(lambda \(k v\)
\(print k\)
\(print v\)\)
\*h\*\)\(hash\-for\-each h
\(lambda \(k v\)
\(printf "~a~n" k\)
\(printf "~a~n" v\)\)\); also dict\-for\-each
\(doseq \[p ih\]
\(println \(first p\)\)
\(println \(second p\)\)\)\(maphash
\(lambda \(k v\)
\(print k\)
\(print v\)\)
h\)[keys and values as lists](https://hyperpolyglot.org/lisp#dict-key-val-lists-note)*none*\(hash\-keys h\)
\(hash\-values h\); also dict\-keys and dict\-values
\(def hkeys \(map \(fn \[p\] \(first p\)\) ih\)\)
\(def hvals \(map \(fn \[p\] \(second p\)\) ih\)\)*none*[user\-defined types](https://hyperpolyglot.org/lisp#user-defined-types-note)common lispracketclojureemacs lisp[defstruct](https://hyperpolyglot.org/lisp#defstruct)\(defstruct account id balance\)\(define\-struct account \(id \(balance \#:mutable\)\)\)\(defstruct account :id :balance\)\(defstruct account id balance\)[struct](https://hyperpolyglot.org/lisp#struct)\(setq a
\(make\-account
:id 3
:balance 17\.12\)\)\(define a \(make\-account 3 17\.12\)\)\(def a \(struct account 3 17\.12\)\)\(setq a
\(make\-account :id 3 :balance 17\.12\)\)[struct getter](https://hyperpolyglot.org/lisp#struct-getter)
\(account\-id a\)\(account\-id a\)\(:id a\)\(account\-id a\)[struct setter](https://hyperpolyglot.org/lisp#struct-setter)
\(setf \(account\-balance a\) 0\)\(set\-account\-balance\! a 0\)*none*\(setf \(account\-balance a\) 0\)[struct predicate](https://hyperpolyglot.org/lisp#struct-predicate)
\(account\-p a\)\(account? a\)*none*\(account\-p a\)[functions](https://hyperpolyglot.org/lisp#functions-note)common lispracketclojureemacs lisp[define function](https://hyperpolyglot.org/lisp#define-function)
\(defun add \(x y\) \(\+ x y\)\)\(define \(add x y\) \(\+ x y\)\)\(defn add \[x y\] \(\+ x y\)\)\(defun add \(x y\) \(\+ x y\)\)can function and variable share name*yes**no**no**yes*[optional argument](https://hyperpolyglot.org/lisp#optional-argument)\(defun add \(a &optional b\)
\(if \(null b\) a \(\+ a b\)\)\)\(define \(add a \(b null\)\)
\(if \(null? b\) a \(\+ a b\)\)\)\(defn add \(\[a\] a\) \(\[a b\] \(\+ a b\)\)\)
*no syntax error if called with more than 2 args:*
\(defn add \[a & \[b\]\]
\(if \(nil? b\) a \(\+ a b\)\)\)\(defun add \(a &optional b\)
\(if \(null b\) a \(\+ a b\)\)\)[variable number of arguments](https://hyperpolyglot.org/lisp#variable-arguments)\(defun add \(a &rest b\)
\(if \(null b\)
a
\(\+ a \(eval \(cons '\+ b\)\)\)\)\)\(define \(add a \. b\)
\(if \(null? b\)
a
\(\+ a \(apply \+ b\)\)\)\)\(defn add \[a & b\]
\(if \(nil? b\) a \(\+ a \(apply \+ b\)\)\)\)\(defun add \(a &rest b\)
\(if \(null b\)
a
\(\+ a \(eval \(cons '\+ b\)\)\)\)\)[default value](https://hyperpolyglot.org/lisp#default-value)\(defun add \(a &optional \(b 0\)\)
\(\+ a b\)\)*racket:*
\(define \(add a \(b 0\)\) \(\+ a b\)\)\(defn add
\(\[a\] \(add a 0\)\)
\(\[a b\] \(\+ a b\)\)\)*none*[named parameter](https://hyperpolyglot.org/lisp#named-parameter)\(defun logarithm \(&key number base\)
\(/ \(log number\) \(log base\)\)\)
\(logarithm :base 2 :number 8\)*none*\(defn logarithm \[\{x :number b :base\}\] \(/ \(Math/log x\) \(Math/log b\)\)\)
\(logarithm \{:base 2 :number 8\}\)\(defun logarithm
\(&key number &key base\)
\(if base
\(/ \(log number\) \(log base\)\)
\(log number\)\)\)
*order significant, not key names:*
\(logarithm :foo 8 :bar 2\)[return multiple values](https://hyperpolyglot.org/lisp#return-multiple-values)\(defun sqrts \(x\)
\(values \(sqrt x\) \(\- \(sqrt x\)\)\)\)\(define \(sqrts x\)
\(values \(sqrt x\) \(\- \(sqrt x\)\)\)\)\(defn sqrts \[x\] \(list \(Math/sqrt x\) \(\- \(Math/sqrt x\)\)\)\)values*creates a list:*
\(defun sqrts \(x\)
\(values \(sqrt x\) \(\- \(sqrt x\)\)\)\)[assign multiple values to local variables](https://hyperpolyglot.org/lisp#multiple-values-local-variables)\(multiple\-value\-bind \(r1 r2\)
\(sqrts 3\)
r2\)\(let\-values
\(\(\(r1 r2\) \(sqrts 3\)\)\)
r2\)\(let \[\[r1 r2\] \(sqrts 3\)\] r2\)\(multiple\-value\-bind
\(r1 r2\)
\(sqrts 3\)
r2\)[assign multiple values to global variables](https://hyperpolyglot.org/lisp#multiple-values-global-variables)\(multiple\-value\-setq \(r1 r2\)
\(sqrts 3\)\)\(define\-values \(r1 r2\) \(sqrts 3\)\)*none*\(multiple\-value\-setq \(r1 r2\) \(sqrts 3\)\)[convert list to multiple values](https://hyperpolyglot.org/lisp#list-to-multiple-values)\(values\-list '\(1 2 3\)\)\(apply values '\(1 2 3\)\)*multiple values are lists**multiple values are lists*[assign multiple values to list](https://hyperpolyglot.org/lisp#multiple-values-list)\(multiple\-value\-list \(sqrts 3\)\)\(call\-with\-values
\(lambda \(\) \(sqrts 3\)\)
list\)*multiple values are lists**multiple values are lists*[tail call optimization](https://hyperpolyglot.org/lisp#tail-call)*yes for sbcl**yes**yes with*recur*no*[lambda](https://hyperpolyglot.org/lisp#lambda)\(lambda \(x\) \(\* x x\)\)\(lambda \(x\) \(\* x x\)\)\#\(\* % %\)
\(fn \[x\] \(\* x x\)\); shortcut notation with two args: \#\(\* %1 %2\)
\(lambda \(x\) \(\* x x\)\)[apply](https://hyperpolyglot.org/lisp#apply)\(\(lambda \(x\) \(\* x x\)\) 2\)
\(apply \#'\(lambda \(x\) \(\* x x\)\) '\(2\)\)\(\(lambda \(x\) \(\* x x\)\) 2\)
\(apply \(lambda \(x\) \(\* x x\)\) '\(2\)\)\(\#\(\* % %\) 2\)
\(\(fn \[x\] \(\* x x\)\) 2\)
\(apply \#\(\* % %\) '\(2\)\)\(\(lambda \(x\) \(\* x x\)\) 2\)
\(apply
\#'\(lambda \(x\) \(\* x x\)\)
'\(2\)\)[execution control](https://hyperpolyglot.org/lisp#execution-control-note)common lispracketclojureemacs lisp[progn](https://hyperpolyglot.org/lisp#progn)
progn prog1 prog2begin*none**none*
*r6rs:*
begin begin0*none*do*none**none*progn prog1 prog2[loop](https://hyperpolyglot.org/lisp#loop)\(setq i 1\)
\(loop \(print "hello"\)
\(if \(\> i 10\)
\(return\)
\(setq i \(\+ i 1\)\)\)\)*none, use recursion*\(loop \[i 1\]
\(if \(<= i 10\)
\(do \(println "hello"\)
\(recur \(\+ i 1\)\)\)\)\)\(setq i 1\)
\(loop \(print "hello"\)
\(if \(\> i 10\)
\(return\)
\(setq i \(\+ i 1\)\)\)\)[do](https://hyperpolyglot.org/lisp#do)\(do \(\(i 1\) \(sum 0\)\)
\(\(\> i 100\) sum\)
\(setq sum \(\+ sum i\)\)
\(setq i \(\+ i 1\)\)\)
do\**initializes serially**none**none*\(do \(\(i 1\) \(sum 0\)\)
\(\(\> i 100\) sum\)
\(setq sum \(\+ sum i\)\)
\(setq i \(\+ i 1\)\)\)
do\**initializes sequentially*[dotimes](https://hyperpolyglot.org/lisp#dotimes)\(dotimes \(i 10 nil\)
\(format t "hello~%"\)\)*none*\(dotimes \[\_ 10\]
\(println "hello"\)\)\(dotimes \(i 10 nil\)
\(print "hello\\n"\)\)[if](https://hyperpolyglot.org/lisp#if)
\(if \(< x 0\) \(\- x\) x\)\(if \(< x 0\) \(\- x\) x\)\(if \(< x 0\) \(\- x\) x\)\(if \(< x 0\) \(\- x\) x\)[when](https://hyperpolyglot.org/lisp#when)\(when \(< x y\)
\(print "x is less "\)
\(print "than y"\)\)*racket:*
\(when \(< x y\)
\(display "x is less "\)
\(display "than y"\)\)\(when \(< x y\)
\(println "x is less "\)
\(println "than y"\)\)\(when \(< x y\)
\(print "x is less "\)
\(print "than y"\)\)[cond](https://hyperpolyglot.org/lisp#cond)\(cond \(\(\> x 0\) 1\)
\(\(= x 0\) 0\)
\(t \-1\)\)\(cond \(\(\> x 0\) 1\)
\(\(= x 0\) 0\)
\(else \-1\)\)\(cond \(\> x 0\) 1
\(= x 0\) 0
true \-1\)\(cond \(\(\> x 0\) 1\)
\(\(= x 0\) 0\)
\(t \-1\)\)[lazy evaluation](https://hyperpolyglot.org/lisp#lazy-evaluation)\(define x \(delay \(/ 1 0\)\)\)
\(promise? x\)
\(\+ 1 \(force x\)\)[continuations](https://hyperpolyglot.org/lisp#continuations)\(define cc null\)
\(\+ 1 \(call/cc \(lambda \(x\) \(set\! cc x\) 0\)\)\)
\(cc 5\)[exceptions](https://hyperpolyglot.org/lisp#exceptions-note)common lispracketclojureemacs lisp[error](https://hyperpolyglot.org/lisp#error)
\(error "failed"\)\(error "failed"\)\(throw \(Exception\. "failed"\)\)\(error "failed"\)[handle error](https://hyperpolyglot.org/lisp#handle-error)\(handler\-case
\(error "failed"\)
\(simple\-error \(e\)
\(format t "error: ~a" e\)\)\)\(with\-handlers
\(\(exn:fail?
\(lambda \(e\)
\(printf "error: ~a"
\(exn\-message e\)\)\)\)\)
\(error "failed"\)\)\(try \(throw \(Exception\. "failure"\)\)
\(catch Exception e
\(printf "error: %s"
\(\.getMessage e\)\)\)\)\(condition\-case e
\(error "failed"\)
\(error \(message "error: %s"
\(error\-message\-string e\)\)\)\)[define exception](https://hyperpolyglot.org/lisp#define-exception)\(define\-condition odd\-err \(error\)
\(\(num :accessor odd\-err\-num
:initarg :num\)\)
\(:report
\(lambda \(e s\)
\(format s "odd number: ~a"
\(odd\-err\-num e\)\)\)\)\)\(define exn:odd\-err? "odd number"\)*only symbols and keywords can be thrown and caught*[throw exception](https://hyperpolyglot.org/lisp#throw-exception)\(error 'odd\-err :num 7\)\(raise exn:odd\-err?\)\(throw \(Exception\. "failed"\)\)\(throw 'odd\-err t\)[catch exception](https://hyperpolyglot.org/lisp#catch-exception)\(handler\-case \(/ 1 0\)
\(division\-by\-zero \(\)
\(progn
\(format t "division by zero"\)
nil\)\)\)\(with\-handlers \(\(exn:fail? \(lambda \(e\) \(begin \(printf "division by zero~n"\) null\)\)\)\) \(/ 1 0\)\)\(try \(/ 1 0\) \(catch ArithmeticException \_ \(do \(println "division by zero"\) nil\)\)\)\(catch 'failed \(throw 'failed nil\) t\)[restart\-case](https://hyperpolyglot.org/lisp#restart-case)\(defun halve \(l\)
\(mapcar \(lambda \(x\)
\(restart\-case
\(if \(= \(rem x 2\) 0\) \(/ x 2\)
\(error 'odd\-error :num x\)\)
\(round\-down \(\) \(/ \(\- x 1\) 2\)\)
\(round\-up \(\) \(/ \(\+ x 1\) 2\)\)\)\) l\)\)*none**none*[invoke\-restart](https://hyperpolyglot.org/lisp#invoke-restart)\(handler\-bind
\(\(odd\-err
\(lambda \(c\)
\(invoke\-restart
'round\-down\)\)\)\)
\(halve '\(1 2 4 9\)\)\)*none**none*[finally clause](https://hyperpolyglot.org/lisp#finally-clause)\(unwind\-protect
\(error "failure"\)
\(print "clean up"\)\)*none*\(try \(throw \(Exception\. "failure"\)\)
\(finally \(println "clean up"\)\)\)\(unwind\-protect
\(error "failure"\)
\(print "clean up"\)\)[streams](https://hyperpolyglot.org/lisp#streams-note)common lispracketclojureemacs lisp[standard file handles](https://hyperpolyglot.org/lisp#std-file-handles-note)\*standard\-input\*
\*standard\-output\*
\*error\-output\*\(current\-input\-port\)
\(current\-output\-port\)
\(current\-error\-port\)\*in\*
\*out\*
\*err\*[end\-of\-file behavior](https://hyperpolyglot.org/lisp#eof-note)read\-line*returns two values, the 2nd set to*T*at end\-of\-file\.*EOF\-OF\-FILE*is signaled when reading past end of file\.*
*Returns the value*eof\.*Use*eof\-object?*to test for it\.*
\.readLine*on a*java\.io\.Reader*object returns*nil\.[read line from stdin](https://hyperpolyglot.org/lisp#read-stdin-note)\(setq line \(read\-line\)\)\(let \(\(s \(read\-line\)\)\)
\#\|use s\|\#\)\(let \[s \(read\-line\)\]
\(comment use s\)\)[chomp](https://hyperpolyglot.org/lisp#chomp-note)
read\-line*discards newline*read\-line*discards newline*[write line to stdout](https://hyperpolyglot.org/lisp#println-note)\(defun println \(s\)
\(format t "~a~%" s\)\)
\(println "hello"\)\(write\-string s\)
\(newline\)\(println "hello"\)[write formatted string to stdout](https://hyperpolyglot.org/lisp#format-stdout-note)\(format t "~s ~d: ~2$~%"
"foo"
7
13\.7\)\(printf "~a ~a: ~a~n"
"foo"
7
\(/ \(round \(\* 13\.7 100\)\) 100\)\)\(printf "%s %d %\.2f\\n" "foo" 7 13\.7\)[open file for reading](https://hyperpolyglot.org/lisp#open-file-note)\(setq in \(open "/etc/hosts"\)\)\(let
\(\(f \(open\-input\-file "/etc/hosts"\)\)\)
\#\| use f\|\#\); f is java\.io\.Reader object:
\(let \[f \(clojure\.java\.io/reader "/etc/hosts"\)\]
\(\.readLine f\)\)[open file for writing](https://hyperpolyglot.org/lisp#open-file-write-note)\(setq out \(open "/tmp/test" :direction :output :if\-exists :supersede\)\)\(let
\(\(f \(open\-output\-file
"/tmp/foo"
\#:exists 'truncate\)\)\)
\#\| use f\|\#\); f is java\.io\.Writer object:
\(let \[f \(clojure\.java\.io/writer "/tmp/foo"\)\]
\(\.write f "lorem ipsum\\n"\)
\(\.close f\)\)[open file for appending](https://hyperpolyglot.org/lisp#open-file-append-note)\(setq out \(open "/tmp/test" :direction :output :if\-exists :append\)\)\(let
\(\(f \(open\-output\-file
"/tmp/foo"
\#:exists 'append\)\)\)
\#\| use f\|\#\)\(let \[f \(clojure\.java\.io/writer "/tmp/foo"
:append true\)\]
\(\.write f "lorem ipsum\\n"\)
\(\.close f\)\)[close file](https://hyperpolyglot.org/lisp#close-file-note)
\(close in\)\(close\-input\-port f\)
\(close\-output\-port f\)\(\.close f\)[close file implicitly](https://hyperpolyglot.org/lisp#close-file-implicitly-note)\(with\-open\-file \(out \#P"/tmp/test" :direction :output\) \(write\-line "lorem ipsum" out\)\)\(call\-with\-input\-file
"/etc/hosts"
\(lambda \(f\) \(\#\| use f\|\#\)\); also call\-with\-output\-file
\(with\-open \[f
\(clojure\.java\.io/reader "/etc/hosts"\)\]
\(comment use f\)\)[read line](https://hyperpolyglot.org/lisp#read-line-note)
\(setq line \(read\-line f\)\)\(define line \(read\-line in\)\)\(\.readLine f\)[iterate over file by line](https://hyperpolyglot.org/lisp#iterate-file-note)\(for \(\[line \(in\-lines
\(open\-input\-file
"/etc/hosts"\)\)\]\)
\(write\-string line\)
\(newline\)\)\(loop \[line \(\.readLine f\)\]
\(if \(not= line nil\)
\(do \(println line\)
\(recur \(\.readLine f\)\)\)\)\)[read file into array of strings](https://hyperpolyglot.org/lisp#read-file-array-note); to list of strings:
\(sequence\-\>list \(in\-lines
\(open\-input\-file "/etc/hosts"\)\)\)\(vec \(line\-seq f\)\)[read file into string](https://hyperpolyglot.org/lisp#read-file-str-note)\(define s \(file\-\>string "/etc/hosts"\)\)\(let \[s \(slurp "/etc/hosts"\)\]
\(print s\)\)[write string](https://hyperpolyglot.org/lisp#write-str-note)
\(write\-string s f\)\(\.write f s\)[write line](https://hyperpolyglot.org/lisp#write-line-note)\(write\-string s f\)
\(newline f\)\(\.write f \(println\-str s\)\)[flush file handle](https://hyperpolyglot.org/lisp#flush-file-note)
\(flush\-output f\)\(f \.flush\)[file handle position](https://hyperpolyglot.org/lisp#seek-note)*get, set*
; Evaluates to non\-negative integer:
\(file\-position f\); Sets next read or write ; to beginning of file: \(file\-position f 0\)
; arg is characters from current position;
; moving backward not possible:
\(\.skip f 1000\); arg is max characters to buffer: \(\.mark f 1000000\) ; move to position saved when \.mark was called: \(\.rest f\)
[in memory stream](https://hyperpolyglot.org/lisp#in-memory-stream-note)\(setq f \(make\-string\-input\-stream
"lorem ipsum"\)\)
\(read\-line f\)\(setq f2 \(make\-string\-output\-stream\) \(write\-string "lorem ipsum\) \(get\-output\-stream\-string out\)
\(define f \(open\-input\-string "lorem ipsum"\)\)
\(read\-line f\)\(define f2 \(open\-output\-string\)\) \(write\-string "lorem ipsum" f2\) \(get\-output\-string f2\)
; use \*in\* to read from string:
\(with\-in\-str "lorem ispum"
\(read\-line\)\); use \*out\* to write to string: \(with\-out\-str \(println "lorem ipsum"\)\)
[emacs buffers](https://hyperpolyglot.org/lisp#emacs-buffers-note)emacs lisp[list buffers](https://hyperpolyglot.org/lisp#list-buffers-note);; list of buffer objects:
\(buffer\-list\);; name of first buffer in list: \(buffer\-name \(car \(buffer\-list\)\)\)
;; name of current buffer: \(buffer\-name \(current\-buffer\)\)
[current buffer](https://hyperpolyglot.org/lisp#current-buffer-note)
*get and set*;; name of current buffer:
\(buffer\-name \(current\-buffer\)\);; open in current pane: \(switch\-to\-buffer "foo\.txt"\)
;; open in other pane: \(switch\-to\-buffer\-other\-window "bar\.txt"\)
[clear buffer](https://hyperpolyglot.org/lisp#clear-buffer-note);; current buffer:
\(erase\-buffer\);; buffer named "foo\.txt: \(with\-current\-buffer "foo\.txt" \(erase\-buffer\)\)
[point](https://hyperpolyglot.org/lisp#point-note)
*get and set*;; 1\-based index of char under cursor:
\(point\);; go to beginning of current buffer: \(goto\-char 1\)
;; go to end of current buffer: \(goto\-char \(buffer\-size\)\)
search and set point;; Set point to character after string\.
;; 1st arg is position in buffer beyond
;;which search stops\.
;; If 2nd arg is true, return nil
;;on failure, otherwise raise error\.
;; 3rd argument is the occurrence
;;of the string, if negative
;;search backwards from point\.
\(search\-forward "lorem" nil t 1\)insert at string point;; takes 1 or more args:
\(insert "lorem" " ipsum"\)current buffer as string\(buffer\-string\)insert file contents at point\(insert\-file "/etc/passwd"\)[mark](https://hyperpolyglot.org/lisp#mark-note)
*get and set*;; to beginning of current buffer:
\(set\-mark 1\);; to point of current buffer: \(set\-mark \(point\)\)
[files](https://hyperpolyglot.org/lisp#files-note)common lispracketclojureemacs lisp[file test, regular file test](https://hyperpolyglot.org/lisp#file-test-note)\(osicat:file\-exists\-p "/tmp/foo"\)
\(osicat:regular\-file\-exists\-p "/tmp/foo"\)*??*
\(file\-exists? "/etc/hosts"\)\(\.exists \(io/file "/etc/hosts"\)\)\(file\-exists\-p "/etc/hosts"\)\(file\-regular\-p "/etc/hosts"\)
[file size](https://hyperpolyglot.org/lisp#file-size-note)\(file\-size "/etc/hosts"\)\(\.length \(io/file "/etc/hosts"\)\)\(eighth
\(file\-attributes "/etc/hosts"\)\)[is file readable, writable, executable](https://hyperpolyglot.org/lisp#file-readable-writable-executable-note)\(pair? \(filter
\(lambda \(x\) \(eq? x 'read\)\)
\(file\-or\-directory\-permissions
"/etc/hosts"\)\)\)
\(pair? \(filter
\(lambda \(x\) \(eq? x 'write\)\)
\(file\-or\-directory\-permissions
"/etc/hosts"\)\)\)
\(pair? \(filter
\(lambda \(x\) \(eq? x 'execute\)\)
\(file\-or\-directory\-permissions
"/etc/hosts"\)\)\)\(\.canRead \(io/file "/etc/hosts"\)\)
\(\.canWrite \(io/file "/etc/hosts"\)\)
\(\.canExecute \(io/file "/etc/hosts"\)\)[set file permissions](https://hyperpolyglot.org/lisp#chmod-note)\(file\-or\-directory\-permissions
"/tmp/foo"
\#o755\)\(set\-file\-modes "/tmp/foo" \#o755\)[last modification time](https://hyperpolyglot.org/lisp#last-modification-time-note)\(file\-or\-directory\-modify\-seconds "/tmp/foo"\); Unix epoch in milliseconds:
\(\.lastModified \(java\.io\.File\. "/tmp/foo"\)\)[copy file, remove file, rename file](https://hyperpolyglot.org/lisp#cp-rm-mv-note)\(cl\-fad:copy\-file \#P"/tmp/foo"
\#P"/tmp/bar"\)\(delete\-file \#P"/tmp/foo"\)
\(rename\-file \#P"/tmp/bar" \#P"/tmp/foo"\)
\(copy\-file "/tmp/foo" "/tmp/bar"\)
\(delete\-file "/tmp/foo"\)
\(rename\-file\-or\-directory
"/tmp/bar"
"/tmp/foo"\)\(clojure\.java\.io/copy
\(java\.io\.File\. "/tmp/foo"\)
\(java\.io\.File\. "/tmp/bar"\)\)
\(clojure\.java\.io/delete\-file "/tmp/foo"\)
\(\.renameTo \(java\.io\.File\. "/tmp/bar"\)
\(java\.io\.File\. "/tmp/foo"\)\)\(copy\-file "/tmp/foo" "/tmp/bar"\)
\(delete\-file "/tmp/foo"\)
\(rename\-file "/tmp/bar" "/tmp/foo"\)[create symlink, symlink test, get target](https://hyperpolyglot.org/lisp#symlink-note)\(osicat:make\-link "/tmp/hosts" :target "/etc/hosts"\)\(make\-file\-or\-directory\-link
"/etc/hosts"
"/tmp/hosts"\)
\(link\-exists? "/tmp/hosts"\)
*??*\(make\-symbolic\-link "/etc/hosts" /tmp/hosts"\)
*returns target if symlink or nil:*
\(file\-symlink\-p "/tmp/hosts"\)[temporary file](https://hyperpolyglot.org/lisp#tmp-file-note)\(define tmp \(make\-temporary\-file\)\)
\(path\-\>string tmp\); java\.io\.File:
\(java\.io\.File/createTempFile "foo" "\.txt"\)\(make\-temp\-file "foo"\)[directories](https://hyperpolyglot.org/lisp#directories-note)common lispracketclojureemacs lisp[build pathname](https://hyperpolyglot.org/lisp#build-pathname-note)\(make\-pathname
:directory '\(:absolute "etc"\)
:name "hosts"\); returns path; convert to string
; with path\-\>string:
\(build\-path "/etc" "hosts"\)\(require '\[clojure\.java\.io :as io\]\); returns java\.io\.File; ; convert to string with \.getPath: \(io/file "/etc" "hosts"\)
[dirname and basename](https://hyperpolyglot.org/lisp#dirname-basename-note)\(pathname\-directory \#P"/etc/hosts"\)\(pathname\-name \#P"/etc/hosts"\)
\(let\-values \(\(\(dir file \_\)
\(split\-path "/etc/hosts"\)\)\)
\#\| use dir or file\|\#\)\(require '\[clojure\.java\.io :as io\]\)\(\.getParent \(io/file "/etc/hosts"\)\) \(\.getName \(io/file "/etc/hosts"\)\)
\(file\-name\-directory "/etc/hosts"\)\(file\-name\-nondirectory "/etc/hosts"\)
[absolute pathname](https://hyperpolyglot.org/lisp#abs-pathname-note)\(simplify\-path
\(path\-\>complete\-path "\.\."\)\)\(\.getCanonicalPath \(java\.io\.File\. "\.\."\)\)\(expand\-file\-name "\.\."\)[iterate over directory by file](https://hyperpolyglot.org/lisp#iterate-dir-note)\(dolist \(file \(osicat:list\-directory "/tmp"\)\) \(format t "~a~%" file\)\)\(for \(\[path \(directory\-list "/etc"\)\]\)
\(write\-string
\(path\-\>string path\)\)\); file\-seq returns java\.io\.File objects for files
; in arg directory and any subdirs recursively\.
\(filter \#\(= \(\.getParent %\) "/etc"\)
\(file\-seq \(clojure\.java\.io/file "/etc"\)\)\)\(dolist
\(file \(directory\-files "/etc"\)\)
\(print file\)\)\)[make directory](https://hyperpolyglot.org/lisp#mkdir-note)\(make\-directory\* "/tmp/foo/bar"\)\(require '\[clojure\.java\.io :as io\]\)\(\.mkdir \(io/file "/tmp/foo"\)\)
*creates parents if 2nd arg non\-nil:*
\(make\-directory "/tmp/foo/bar" t\)[recursive copy](https://hyperpolyglot.org/lisp#recursive-cp-note)\(copy\-directory/files "/tmp/foo\.d"
"/tmp/bar\.d"\)[remove empty directory](https://hyperpolyglot.org/lisp#rmdir-note)\(delete\-directory "/tmp/foo\.d"\)\(delete\-directory "/tmp/foo\.d"\)\(clojure\.java\.io/delete\-file "/tmp/foo\.d"\)\(delete\-directory "/tmp/foo\.d"\)[remove directory and contents](https://hyperpolyglot.org/lisp#rm-rf-note)\(osicat:delete\-directory\-and\-files "/tmp/foo\.d"\)\(delete\-directory/files "/tmp/foo\.d"\)\(delete\-directory "/tmp/foo\.d" t\)[directory test](https://hyperpolyglot.org/lisp#dir-test-note)\(osicat:directory\-exists\-p \#P"/etc"\)\(directory\-exists? "/etc"\)\(\.isDirectory \(io/file "/etc"\)\)\(file\-directory\-p "/etc"\)[processes and environment](https://hyperpolyglot.org/lisp#processes-environment-note)common lispracketclojureemacs lisp[command line arguments](https://hyperpolyglot.org/lisp#cmd-line-arg-note)\*posix\-argv\*current\-command\-line\-arguments\*command\-line\-args\**in shebang mode only:*
command\-line\-args*or*argv[program name](https://hyperpolyglot.org/lisp#program-name-note)[environment variables](https://hyperpolyglot.org/lisp#env-var-note)\(posix\-getenv "HOME"\)\(getenv "HOME"\)\(System/getenv "HOME"\)\(getenv "HOME"\)[user id and name](https://hyperpolyglot.org/lisp#user-id-name-note)[exit](https://hyperpolyglot.org/lisp#exit-note)[external command](https://hyperpolyglot.org/lisp#external-cmd-note)\(run\-program "ls" '\( "/etc"\)\)\(require scheme/system\)
\(system "ls /etc"\)\(\.exec \(Runtime/getRuntime\) "ls"\)\(shell\-command "ls /etc"\)[command substitution](https://hyperpolyglot.org/lisp#cmd-subst-note)\(shell\-command\-to\-string "ls /etc"\)[libraries and namespaces](https://hyperpolyglot.org/lisp#libraries-namespaces-note)common lispracketclojureemacs lispcomplete example$ cat b/a\.clj
\(ns b\.a\)
\(def x 3\)$ java \-cp clojure\.jar:\. clojure\.main =\> \(require 'b\.a\) =\> b\.a/x 3
compile library\(compile\-file "a\.lisp"\)$ raco make a\.rkt\(compile 'a\)$ emacs \-batch \-Q \-L \. \\
\-f batch\-byte\-compile a\.elload library
\(load "a\.lisp"\)\(require a\)\(require 'a\)\(require "a"\)load library in subdirectory\(load "b/a\.lisp"\)\(require "b/a\.rkt"\)\(require 'b\.a\)hot patch\(load "a\.lisp"\)*none*\(require 'b\.a :reload\)\(load "a"\)load error*raises*sb\-int:simple\-file\-error*raises*exn:fail:syntax:missing\-module\.*Because*require*must be top\-level, the exception cannot be handled\.**raises*FileNotFoundException*raises*file\-errlibrary path*contains working directory at startup*\(require setup/dirs\)\(get\-collects\-search\-dirs\)
*same as path used by java VM*; adds directory to library path:
\(add\-to\-list 'load\-path \("/home/ed/\.emacs\.d/lib"\)\)library path environment variable*none*CLASSPATHEMACSLOADPATHlibrary path command line option*none*$ java \-cp /foo/bar:/baz/quux$ emacs \-L /foo/barnamespace declaration\(defpackage :foo\)\(module mconst racket
\(provide pi\)
\(define pi 3\.14\)\)\(ns mconst\)*No namespaces; a common convention is to use a prefix on all identifiers in a library, separated from the rest of the identifier by a hyphen\.*subnamespace declaration*none*; must be in b/a\.clj:
\(ns b\.a\)namespace separator::\.*and*/import definitions; set current \*package\* to foo and import symbol twiddle from bar:
\(defpackage :foo
\(:import\-from :bar :twiddle\)\)import all definitions in namespace; set current \*package\* to foo and import symbols from bar:
\(defpackage :foo
\(:use :bar\)\)namespace shadow avoidanceidentifier shadow avoidancepackage manager help$ raco help
$ raco pkg\-\-help
$ raco pkg install\-\-helplist installed packages$ raco pkg show\-\-allM\-x list packagessearch packages\(ql:system\-apropos "time"\)[http://pkgs\.racket\-lang\.org](http://pkgs.racket-lang.org/)M\-x list\-packagesinstall package; install quicklisp
\(load "~/quicklisp/setup\.lisp"\)
\(ql:quickload "osicat"\)$ raco pkg install\-\-deps search\-auto srfi*Use*M\-x list\-packages*to bring up the package menu;*i*to select a package to install, and*x*to install it\.*remove package$ raco pkg remove srfi*In the package menu, use*d*to select a package to uninstall and*x*to uninstall it\.*[objects](https://hyperpolyglot.org/lisp#objects-note)common lispracketclojureemacs lisp[define class](https://hyperpolyglot.org/lisp#defclass)\(defclass rectangle \(\)
\(
\(height
:accessor rectangle\-height
:initarg :height\)
\(width
:accessor rectangle\-width
:initarg :width\)\)\)\(define rectangle%
\(class object%
\(init width\)
\(init height\)
\(super\-new\)
\(define curr\-height height\)
\(define curr\-width width\)
\(define/public \(get\-height\)
curr\-height\)
\(define/public \(get\-width\)
curr\-width\)
\(define/public \(set\-height ht\)
\(set\! curr\-height ht\)\)
\(define/public \(set\-width wd\)
\(set\! curr\-width wd\)\)\)\)*use java:*
public class Rectangle \{
public float height;
public float width;
public Rectangle\(float h, float w\) \{
this\.height = h;
this\.width = w;
\}
public void setHeight\(float h\) \{
this\.height = h;
\}
public void setWidth\(float w\) \{
this\.width = w;
\}[make instance](https://hyperpolyglot.org/lisp#make-instance)\(make\-instance 'rectangle
:height 3
:width 7\)\(define rect
\(new rectangle
\(height 7\)
\(width 3\)\)\)\(import 'Rectangle\)
\(def r \(Rectangle\. 7 3\)\)[read attribute](https://hyperpolyglot.org/lisp#read-attribute)
\(rectangle\-height rect\)\(send rect get\-height\)\(\.height r\)[write attribute](https://hyperpolyglot.org/lisp#write-attribute)
\(setf \(rectangle\-height rect\) 4\)\(send rect set\-height 4\)\(\.setHeight r 8\)[define method](https://hyperpolyglot.org/lisp#defmethod)\(defmethod area \(\(figure rectangle\)\)
\(\* \(rectangle\-height figure\)
\(rectangle\-width figure\)\)\)\(define/public \(area\)
\(\* curr\-height curr\-width\)\)\(defmulti area class\)
\(defmethod area Rectangle \[r\] \(\* \(\.height r\) \(\.width r\)\)\)[invoke method](https://hyperpolyglot.org/lisp#invoke-method)
\(area rect\)\(send rect area\)\(area r\)[universal superclass](https://hyperpolyglot.org/lisp#universal-superclass)standard\-object tobject%Object[multiple inheritance](https://hyperpolyglot.org/lisp#multiple-inheritance)yesno*only one direct superclass; can implement multiple interfaces*[lisp macros](https://hyperpolyglot.org/lisp#lisp-macros-note)common lispracketclojureemacs lisp[backquote and comma](https://hyperpolyglot.org/lisp#backquote-comma)\(setq op '\+\)
\(eval\`\(,op 1 1\)\)\(define op '\+\)
\(eval\`\(,op 1 1\)\)
\(eval \(quasiquote \(\(unquote op\) 1 1\)\)\)\(def op \+\)
\(eval\`\(,op 1 1\)\)\(setq op '\+\)
\(eval\`\(,op 1 1\)\)[defmacro](https://hyperpolyglot.org/lisp#defmacro)\(defmacro rpn \(arg1 arg2 op\)
\(list op arg1 arg2\)\)\(define\-syntax\-rule \(rpn arg1 arg2 op\) \(op arg1 arg2\)\)\(defmacro rpn \[arg1 arg2 op\]
\(list op arg1 arg2\)\)\(defmacro rpn \(arg1 arg2 op\)
\(list op arg1 arg2\)\)[defmacro w/ backquote](https://hyperpolyglot.org/lisp#defmacro-backquote)\(defmacro rpn \(arg1 arg2 op\)
\`\(,op ,arg1 ,arg2\)\)\(define\-syntax\-rule \(rpn3 arg1 arg2 op\)
\(eval ‘\(,op ,arg1 ,arg2\)\)\)\(defmacro rpn \[arg1 arg2 op\]\`\(~op ~arg1 ~arg2\)\)\(defmacro rpn \(arg1 arg2 op\)
\`\(,op ,arg1 ,arg2\)\)[macro predicate](https://hyperpolyglot.org/lisp#macro-predicate)\(macro\-function rpn\)*none**none**none*[macroexpand](https://hyperpolyglot.org/lisp#macroexpand)\(macroexpand ’\(rpn 1 2 \+\)\)\(syntax\-object\-\>datum \(expand\-to\-top\-form '\(rpn 1 2 \+\)\)\)\(macroexpand '\(rpn 1 2 \+\)\)\(macroexpand '\(rpn 1 2 \+\)\)[splice quote](https://hyperpolyglot.org/lisp#splice-quote)\(defmacro add \( &rest args \)
\`\(\+ ,@args\)\)\(define\-syntax\-rule \( add first …\) \(\+ first …\)\)\(defmacro add \[ & args \]\`\(\+ ~@args\)\)\(defmacro add \( &rest args \)
\`\(\+ ,@args\)\)[recursive macro](https://hyperpolyglot.org/lisp#recursive-macro)\(defmacro add \(a &rest b\)
\`\(if \(null ',b\)
\(\+ ,a\)
\(\+ ,a \(add ,@b\)\)\)\)\(define\-syntax add \(syntax\-rules \(\)
\[\(add x\) x\]
\[\(add x y\) \(\+ x y\)\]
\[\(add x y …\) \(\+ x \(add y …\)\)\]\)\)\(defmacro add \(\[a\]\`\(\+ ~a\)\) \(\[a & b\]\`\(\+ ~a \(add ~@b\)\)\)\)\(defmacro add \(a &rest b\)
\`\(if \(null ',b\)
\(\+ ,a\)
\(\+ ,a \(add ,@b\)\)\)\)[hygienic](https://hyperpolyglot.org/lisp#hygienic)
*no**yes**with*\#*suffix**no*[local values](https://hyperpolyglot.org/lisp#local-values)\(defmacro square\-sum \(x y\)
\(let \(\(sum \(gensym\)\)\)
\`\(let \(\(,sum \(\+ ,x ,y\)\)\)
\(\* ,sum ,sum\)\)\)\)\(define\-syntax\-rule \(square\-sum x y\)
\(let \(\(sum \(\+ x y\)\)\)
\(\* sum sum\)\)\)\(defmacro two\-list \[x\]\`\(let \[arg\# ~x\] \(list arg\# arg\#\)\)\)\(defmacro square\-sum \(x y\)
\(let \(\(sum \(gensym\)\)\)
\`\(let \(\(,sum \(\+ ,x ,y\)\)\)
\(\* ,sum ,sum\)\)\)\)[reflection](https://hyperpolyglot.org/lisp#reflection-note)common lispracketclojureemacs lispinspect type
\(type\-of '\(1 2 3\)\)
\(typep '\(1 2 3\) 'list\)
\(listp '\(1 2 3\)\)\(list? '\(1 2 3\)\)\(= \(type 1\) java\.lang\.Long\)
\(= \(class 1\) java\.lang\.Long\)
\(integer? 1\)\(type\-of \[1 2 3\] 'vector\)
\(typep \[1 2 3\] 'vector\)
\(vectorp \[1 2 3\]\)instance\-ofinstance?basic types*logical and numeric:*
bignum bit complex double\-float fixnum float integer long\-float nil null number ratio rational real short\-float signed\-btye single\-float t unsigned\-byte*symbols and strings:* base\-character character extended\-character keyword simple\-string standard\-char string symbol
*data structures:* array atom bit\-vector cons hash\-table list sequence simple\-array simple\-bit\-vector simple\-vector vector
*other:* compiled\-function function package pathname random\-state stream
[sequence data types](https://hyperpolyglot.org/lisp#sequence-data-types)list vectorlist vector hash\-table string input\-port rangeall collections and stringslist vector[get docstring](https://hyperpolyglot.org/lisp#docstring-note)
\(describe \#'mapcar\)*none*\(doc map\)\(describe\-function 'mapcar\)[define function with docstring](https://hyperpolyglot.org/lisp#define-docstring-note)\(defun add \(x y\)
"add x and y"
\(\+ x y\)\)*none*\(defn add "add x and y" \[x y\]
\(\+ x y\)\)\(defun add \(x y\)
"add x and y"
\(\+ x y\)\)[apropos and documentation search](https://hyperpolyglot.org/lisp#search-doc-note)*none**none*\(apropos \#"^add$"\)
\(find\-doc \#"add \\S\+ and \\S\+"\)\(apropos "^add$"\)
*none*[java interoperation](https://hyperpolyglot.org/lisp#java-interop-note)common lispracketclojureemacs lisp[new](https://hyperpolyglot.org/lisp#java-new)\(def rnd \(new java\.util\.Random\)\)
\(def rnd \(java\.util\.Random\.\)\)[method](https://hyperpolyglot.org/lisp#java-method)\(\. rnd nextFloat\)
\(\.nextFloat rnd\)
\(\. rnd nextInt 10\)
\(\.nextInt rnd 10\)[class method](https://hyperpolyglot.org/lisp#java-class-method)
\(Math/sqrt 2\)[chain](https://hyperpolyglot.org/lisp#java-chain)
[import](https://hyperpolyglot.org/lisp#java-import)\(import '\(java\.util Random\)\)
\(def rnd \(Random\.\)\)[to java array](https://hyperpolyglot.org/lisp#java-to-array)\(to\-array '\(1 2 3\)\)
\(into\-array Integer '\(1 2 3\)\)\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_## [version used](https://hyperpolyglot.org/lisp#version-used)
Versions used to verify examples in the reference sheet\.
## [show version](https://hyperpolyglot.org/lisp#show-version)
How to determine the version\.
## [Grammar and Execution](https://hyperpolyglot.org/lisp#grammar-execution)
## [compiler](https://hyperpolyglot.org/lisp#compiler)
**racket**
Compiling a\.ss creates the byte\-code compiled file a\_ss\.zo, which will be used by*mzscheme*in preference to the source code if it encounters
## [standalone executable](https://hyperpolyglot.org/lisp#standalone-executable)
**racket**
In order for code to be compiled as a standalone executable, it must be packaged as a module\. This can be accomplished by putting the*\#lang scheme*shorthand the top of the file\. All functions that are defined in the module will be executed in order\. Here is a simple example:
```
#lang scheme
(define hello
(printf "Hello world!~n"))
```
**emacs**
[Building Emacs](http://www.gnu.org/s/emacs/manual/html_node/elisp/Building-Emacs.html)
## [interpreter](https://hyperpolyglot.org/lisp#interpreter)
How to interpret the code in a file\.
## [shebang](https://hyperpolyglot.org/lisp#shebang)
How to have a script run by the interpreter automatically\. Replace the given path with the path to the interpreter on your system\.
**emacs lisp**
To run some lisp code from within emacs, use*M\-x load*or*M\-x load\-file*\. The first command will use the list of strings in*load\-path*to search for the file\. It is not necessary to specify the*\.el*or*\.elc*suffix if the file has one\.
The following snippet is an emacs lisp shebang script implementation of*cat*:
```
#!/usr/bin/env emacs --script
(condition-case nil
(let (line)
(while (setq line (read-from-minibuffer ""))
(princ line)
(princ "\n")))
(error nil))
```
An implementation of*echo*:
```
#!/usr/bin/env emacs --script
(condition-case nil
(progn
(dotimes (i (length argv) nil)
(princ (nth i argv))
(princ " "))
(princ "\n"))
(error nil))
```
## [repl](https://hyperpolyglot.org/lisp#repl)
How to invoke the repl from the command line\.
**racket:**
Racket also provides a GUI repl environment called DrRacket\.
**clojure:**
The clojure repl saves the result of each evaluation in the variables \*1, \*2, … and the last exception in \*e\.
## [command line program](https://hyperpolyglot.org/lisp#cmd-ilne-prog)
How to pass in a program to be executed on the command line\.
## [word separator](https://hyperpolyglot.org/lisp#word-separator)
What is used to separate the operator and data of a S\-expression\.
## [identifier characters](https://hyperpolyglot.org/lisp#identifier-char)
In lisps other than clojure, any character can be used in a symbol\. Some characters are special to the reader and must be escaped to include them in a symbol\. The reader will interpret a sequence of characters starting with a digit as a number instead of a symbol, so escaping must be used to create such a symbol\.
**common lisp:**
Common Lisp is case insensitive, and the reader converts all letters to upper case\. A symbol consisting of just periods "\." must be escaped\. Symbols that start and end with an asterisk "\*" may conflict with system defined special variables\.
**racket:**
\#is only disallowed by the reader at the beginning of symbols\. A symbol consisting of a single period must be escaped\.
## [end\-of\-line comment](https://hyperpolyglot.org/lisp#eol-comment)
## [multiple line comment](https://hyperpolyglot.org/lisp#multiple-line-comment)
\#\| \|\# delimited comments in Common Lisp and Scheme can span multiple lines, and thus can be used to comment out code\.
**clojure:**
Code with balanced parens can be commented out in the following manner:
## [Variables and Expressions](https://hyperpolyglot.org/lisp#var-expr)
## [identifier](https://hyperpolyglot.org/lisp#id)
Are identifiers case sensitive; which characters can be used in identifers\.
In Lisp, identifiers are called*symbols*\.
## [quoted identifer](https://hyperpolyglot.org/lisp#quoted-id)
How to quote or escape characters in identifiers which are otherwise prohibited\.
## [local variable](https://hyperpolyglot.org/lisp#local-var)
How to declare a local variable\.
## [global variable](https://hyperpolyglot.org/lisp#global-var)
How to declare a global variable\.
## [remove variable](https://hyperpolyglot.org/lisp#rm-var)
How to remove a variable\.
## [null](https://hyperpolyglot.org/lisp#null)
The null value\.
**common lisp**
niland the empty list'\(\)are identical\.
**racket**
nulland the empty list'\(\)are identical\.
**clojure**
niland the empty list'\(\)are distinct\.
**emacs lisp**
niland the empty list'\(\)are identical\.
## [null test](https://hyperpolyglot.org/lisp#null-test)
How to test whether a value is null\.
## [identifier as value](https://hyperpolyglot.org/lisp#id-as-val)
How to get the value of an identifier\.
In Lisp, identifiers are first class values and can be stored in variables\. When used as an argument, the Lisp interpreter will treat an identifier as the value of the variable associated with the identifier unless special syntax is used\.
## [identifier test](https://hyperpolyglot.org/lisp#id-test)
How to test whether a value is an identifier\.
## [non\-referential identifier](https://hyperpolyglot.org/lisp#non-referential-id)
A non\-referential identifier is an identifier whose value is itself\.
Non\-referential identifiers are called*keywords*in Lisp\. They also appear in Prolog, where they are called*atoms*, and Ruby, where they are called*symbols*\.
A non\-referential identifier can be convenient to use as a key in a dictionary, since it doesn't have to single quote escaped\.
Strings are an alternative to non\-referential identifiers; some languages have string interning which makes the use of strings just as efficient as non\-referential identifiers\.
## [identifier attributes](https://hyperpolyglot.org/lisp#id-attr)
In Common Lisp, there is a dictionary of attributes associated with each identifier called a*property list*\.
Clojure*metadata*is stored with a value which is an instance ofclojure\.lang\.IObj\. Many types are subclasses ofclojure\.lang\.IObj, but integers, floats, and strings are not\. Clojure metadata is immutable: all keys must be set at once and there is no way to remove keys\.
## cell types
The different cell types\. A lisp\-1 only stores a single entity under a symbol in a given environment\. A lisp\-2 stores multiple entities, and which entity a symbol will resolve to depends on how the symbol is used\. In particular, a value and a function can be stored under the same symbol without collision\.
## nil, is \(\) null?, is \(\) symbol?
is true in common lisp and emacs lisp\.
is true in Scheme\.
## keyword
Keywords are pre\-defined symbols that evaluate to their printed representation\. The reader recognizes them by the initial colon, or in the case of Scheme, by the initial "\#:"\. In Scheme it is an error to use a keyword as an expression\.
## atom
*atom*is is a predicate which returns false for cons cells, and true for anything else\. All lists except for the empty list are cons cells\.
**racket**
Scheme lacks*atom*, but*cons?*is its logical negation\.
**clojure**
Clojure lacks cons cells\. Thus*atom*if implemented in the language would always return true\. However,*\(not \(list? x\)\)*is closer to the spirit and certainly more useful\. Because*nil*is not the empty list in clojure there is also ambiguity about what the value of*\(atom \(\)\)*would be\.
## quote
All lisps have a single quote macro abbreviation for*quote*\. Here are identical ways to quote a symbol and a list:
```
(quote a)
'a
(quote (+ 3 7))
'(+ 3 7)
```
*eval*is a one\-sided inverse of*quote*\. If X is arbitrary lisp code, then the following are identical
## eq, equal, =
In his 1960 paper, McCarthy described*eq*as undefined if either or both arguments are not atomic\. Common Lisp and Scheme \(eq?\) return true if the arguments both evaluate to the same list in memory, otherwise false\.*equal*and*equal?*\(Scheme\) return true if the arguments evaluate to lists with the same elements as determined by calling*equal*or*equal?*recursively\.
In Common Lisp and Scheme, = can only be called on numeric arguments\. The predicates for whether a symbol is numeric are*numberp*and*number?*, respectively\.
Clojure dispenses with*eq*and*equal*and defines*=*to be equivalent to the Common Lisp*equal*\.
## car
Because*car*and*cdr*are abbreviations for parts of the word of the IBM 704, there is a trend to replace them with*first*and*rest*\. However,*car*and*cdr*are short, and convenient notation exists for abbreviating nested calls to*car*and*cdr*\.
In terms of*car*,*cdr*, and combinations thereof, here is what the dialects define:
common lispr5rsracketclojureemacs lispcar,firstcarcar,firstfirstcar,firstcadr,secondcadrcadr,secondsecond,fnextcadr,secondcaddr,thirdcaddrcaddr,thirdcaddr,thirdcadddr,fourthcadddrcadddr,fourthcadddr,fourthfifthfifthfifthsixthsixthsixthseventhseventhseventheightheightheighthninthninthninthtenthtenthtenthcdr, restcdrcdr, restrest,nextcdr, restcddrcddrcddrcddrcdddrcdddrcdddrcdddrcddddrcddddrcddddrcddddrcaarcaarcaarffirstcaarcdarcdarcdarnfirstcdar## cdr
**common lisp**
*cdr*and*rest*return*nil*when called on an empty list\.
**racket**
*cdr*and*rest*raise an error when called on an empty list\.
**clojure**
*rest*returns an empty set \(\) when called on an empty or singleton list, whereas*next*returns*nil*\. In clojure, the empty set evaluates as true in a boolean context and*nil*evaluates as false\.
## cons
**clojure**
Clojure does not implement a list as a linked list of cons cells\. The second argument to*cons*must be a list\.
## cond
## lambda
**clojure:**
## label
## apply
## [Arithmetic and Logic](https://hyperpolyglot.org/lisp#arithmetic-logic)
**integers**
Common Lisp and Racket have arbitrary\-precision integers and use them by default\.
Racket provides thefixnumlibrary for access to hardware integers:
```
(require racket/fixnum)
(fx+ 3 7)
```
Operations on Racket fixnums cause an error when they overflow\.
**rationals and floats**
Common Lisp and Racket have arbitrary\-precision rationals\. Racket uses them in a number of cases when Common Lisp uses hardware floats:
Racket provides theflonumlibrary for access to hardware floats:
```
(require racket/flonum)
(fl* 3.1 -7.2)
```
**complex numbers**
Both the real and imaginary part of a Common Lisp complex number will have the same type, but the type can be integer, rational, or float\.
## [true and false](https://hyperpolyglot.org/lisp#true-false)
Literals for true and false\.
## [falsehoods](https://hyperpolyglot.org/lisp#falsehoods)
Values which evaluate to false in a boolean context\.
**racket**
nulland the empty list \{\{'\{\} do not evaluate as false in a boolean context\.
## [logical operators](https://hyperpolyglot.org/lisp#logical-op)
The logical operators\.
## [relational operators](https://hyperpolyglot.org/lisp#relational-op)
Relational operators for performing comparisons\.
## [min and max](https://hyperpolyglot.org/lisp#min-max)
Functions for returning the least and greatest of the arguments\.
## [numeric predicates](https://hyperpolyglot.org/lisp#num-predicates)
A selection of numeric predicates\.
*realp*and*real?*are true of all numbers which have a zero imaginary component\.*floatp*and*inexact?*are true if the number is being stored in a floating point representation\.
**racket:**
The following all evaluate as \#t:
```
(rational? 1.1)
(rational? (sqrt 2))
(rational? pi)
```
## closure of integers under division
The number system that containing the potential results of integer division\. In mathematics, the closure of integers under division is the rationals, and this is true for common lisp, scheme, and clojure as well\.
Emacs lisp performs integer division \(i\.e\. computes the quotient\), so the closure of the integers under division is the integers\.
## [arithmetic operators](https://hyperpolyglot.org/lisp#arith-op)
In Lisp, \+ and \* take zero or more arguments and \- and / take one or more arguments\. With zero arguments \+ and \* return the additive and multiplicative identities 0 and 1\. With one argument \+ and \* return the argument and \- and / return the additive and multiplicative inverses: i\.e\. the negation and the reciprocal\. When evaluating 3 or more arguments \- and / are computed from left to right: i\.e\. \(\- 3 4 5\) is computed as \(\- \(\- 3 4\) 5\)\.
**clojure:**
*Math\.pow*returns a double\.
**emacs:**
Unary division \(i\.e\. computing the reciprocal\) generates a wrong number of arguments error\.
## [transcendental functions](https://hyperpolyglot.org/lisp#transcendental-func)
## [float truncation](https://hyperpolyglot.org/lisp#float-truncation)
For rounding, floor, and ceiling, the return value is integer if the argument is rational and floating point if the argument is floating point, unless otherwise noted\.
**racket:**
*inexact\-\>exact*can be used to convert a float returned by*round*,*ceiling*, or*floor*to an integer\.
**clojure:**
*Math/round*always returns an integer and throws and error if called on a rational\.*Math/floor*and*Math/ceil*can be called on a rational, but always return a float\.
**emacs:**
*round*,*ceiling*, and*floor*return integers\.*fround*,*fceiling*, and*ffloor*return floats\.
## quotient and remainder
## \(sqrt \-2\)
The value of*\(sqrt \-2\)*\. Common lisp and Scheme support complex numbers\. Clojure and Emacs Lisp do not\.
## decomposition of integer, rational, complex
For absolute value, the type of the return value is the same of the type of the argument\.
**racket:**
The*scheme/math*library must be loaded to use*sgn*\.
**clojure:**
*Math/signum*only operates on a float and returns a float
## [random number](https://hyperpolyglot.org/lisp#random-num)
How to generate a random integer, and a random float in a uniform and a normal distribution\.
## [bit operators](https://hyperpolyglot.org/lisp#bit-op)
**racket:**
The bitwise operators implemented by Gambit and Racket are specified in the withdrawn standard[SRFI 33](http://srfi.schemers.org/srfi-33/)\.
**emacs:**
Also has*ash*, which gives a different value when both arguments are negative\.
## [Strings](https://hyperpolyglot.org/lisp#strings)
## character literals
The syntax for character literals\. The first literal uses the letter "a" as an example of how to write a literal for all ASCII printing characters\.
**common lisp:**
Characters are of type standard\-char\. The predicate is*characterp*\.
**racket:**
The predicate is*char?*\.
**clojure:**
Characters are of type java\.lang\.Character\.
**emacs:**
Characters are of type integer and can be manipulated by arithmetic operators\.*characterp*and*integerp*are synonyms\.
## string literal
The syntax for a string literal\.
## string escapes
A list of escape sequences that can be used in string literals\.
**emacs lisp:**
The \\x escape sequence is followed by one to six hex digits\. Because a variable number of hex digits can be used, it may be necessary to indicate the end of the sequence with a backslash and a space, e\.g\. the following string literal is "λ123":
## character access
How to get the character at a given position in a string\.
## find substring
Find the location of a substring in a string\.
## extract substring
## length
## constructors
## comparison
**common lisp:**
Here is the complete list of string comparison functions:
```
string=
string<
string>
string<=
string>=
string/=
```
There are also case insensitive versions of the above functions:
```
string-equal
string-lessp
string-greaterp
string-not-greaterp
string-not-lessp
string-not-equal
```
**racket:**
Case sensitive string comparison:
```
string<=?
string<?
string=?
string>=?
string>?
```
Case insensitive string comparison:
```
string-ci<=?
string-ci<?
string-ci=?
string-ci>=?
string-ci>?
```
**emacs lisp:**
Emacs has only these string comparison functions, all of which are case sensitive:
```
string=
string-equal
string<
string-lessp
```
*string=*and*string\-equal*are synonyms, as are*string<*and*string\-lessp*\.
## case
## trim
**emacs:**
An implementation oftrim:
```
(defun trim (s)
(let ((s1 (replace-regexp-in-string "[ \t]*$" "" s)))
(replace-regexp-in-string "^[ \t]*" "" s1)))
```
## convert from string, to string
How to convert strings to numbers, and numbers to strings\.
**common lisp:**
*read\-from\-string*invokes the reader, so the return value is not guaranteed to be a floating point number\.
Here is a*parse\-float*function which will convert all real numeric types to floats and raise a simple error if another condition is encountered\.
```
(defun parse-float (s)
(let ((readval (handler-case
(read-from-string s)
(sb-int:simple-reader-error nil)
(end-of-file nil))))
(cond ((realp readval ) (+ readval 0.0))
(t (error (concatenate 'string "not a float: " s))))))
```
## concat
## split
## join
## format
## [Regular Expressions](https://hyperpolyglot.org/lisp#regexes)
## regular expressions
**common lisp**
[http://weitz\.de/cl\-ppcre/](http://weitz.de/cl-ppcre/)
**emacs lisp**
*string\-match*returns the first index of the first matching substring, or nil\.
The following code moves the point to next position following the point that matches the argument, and returns the index of the that position\.
```
(re-search-forward "hello")
```
## regex substitution
## regex special characters
## [Dates and Time](https://hyperpolyglot.org/lisp#dates-time)
## [current datetime](https://hyperpolyglot.org/lisp#current-datetime)
## [current unix epoch](https://hyperpolyglot.org/lisp#current-unix-epoch)
## [unix epoch to broken\-down datetime](https://hyperpolyglot.org/lisp#broken-down-datetime-to-unix-epoch)
## [broken\-down datetime to unix epoch](https://hyperpolyglot.org/lisp#unix-epoch-to-broken-down-datetime)
## [format datetime](https://hyperpolyglot.org/lisp#fmt-datetime)
## [parse datetime](https://hyperpolyglot.org/lisp#parse-datetime)
## [date parts](https://hyperpolyglot.org/lisp#date-parts)
## [time parts](https://hyperpolyglot.org/lisp#time-parts)
## [build broken\-down datetime](https://hyperpolyglot.org/lisp#build-datetime)
## [Lists](https://hyperpolyglot.org/lisp#lists)
## list literal
## pair literal
## \(car '\(\)\)
## \(cdr '\(\)\)
## \(eval '\(\)\)
A practical advantage of having*\(eval '\(\)\)*be equal to '\(\) is that the empty list doesn't have to be quoted\.
## list functions
## nth
*nth*and*list\-ref*count from zero\.*nth*returns*nil*if the index is too large\.*list\-ref*throws an error\.
## index of list element
How to get the index of a list element\. The first element of a list has an index of zero\.
## last butlast
In clojure,*last*and*butlast*are analogs of*first*and*rest*which operate at the end of a list\. If X is a list, then the following code pairs are identities:
```
(last X)
(first (reverse X))
(butlast X)
(reverse (rest (reverse X)))
```
The analogy breaks down in Common Lisp because*last*returns a list with a single element\.
## set\-car set\-cdr
**common lisp:**
The following code pairs perform the same operation on the list:
```
(setf (car l) 3)
(rplaca l 3)
(setf (cdr l) '(4 5 6))
(rplacd l '(4 5 6))
```
However, they are not identical because*rplaca*and*rplacd*return the modified list instead of their 2nd argument\.
**racket:**
Racket provides a separate interpreter*plt\-r5rs*for an R5RS compliant version of Scheme\. Also, the language can be set to R5RS within DrRacket\.
**emacs lisp:**
Also has*setf*\.
## sort
## assoc
**clojure**
In Clojure,*assoc*returns a new association with the specified values replaced:
```
(def numbers {1 :one 2 :two 3 :three 4 :four})
(def jumble (assoc numbers 1 :uno 3 :drei 4 :quatre))
```
## getf
**racket:**
How to implement*getf*in Scheme:
```
(define (getf lst key (default null))
(cond ((null? lst) default)
((null? (cdr lst)) default)
((eq? (car lst) key) (cadr lst))
(else (getf (cddr lst) key default))))
```
## map
**common lisp**
The lambda can accept multiple arguments:
```
(mapcar '+ '(1 2 3) '(4 5 6))
```
**racket**
```
(map + '(1 2 3) '(4 5 6))
```
**clojure**
```
(map + '(1 2 3) '(4 5 6))
```
**emacs lisp**
*mapcar*does not accept multiple argument lambdas
## filter
**common lisp**
Also the negative version:
```
(remove-if (lambda (x) (> x 2)) '(1 2 3))
```
**clojure**
Also the negative version:
```
(remove #(> % 2) '(1 2 3))
```
**emacs lisp**
Also has negative version:
```
(remove-if (λ (x) (> x 2)) '(1 2 3))
```
## reduce \(left fold\)
## right fold
**clojure:**
How to definefoldr:
```
(defn foldr [f init list] (reduce #(f %2 %1) (reverse list)))
```
## sublis
How to apply the mapping defined by an associative list to a recursive list\.
## dolist
## take
Here is how to define*take*for common lisp or emacs lisp:
```
(defun take (n l)
(cond ((< n 0) (error "index negative"))
((= n 0) ())
((null l) (error "index too large"))
(t (cons (car l) (take (- n 1) (cdr l))))))
```
## drop
## push and pop
**racket:**
Here is an implementation of*push*and*pop*in Racket using boxes:
```
(define (push x a-list)
(set-box! a-list (cons x (unbox a-list))))
(define (pop a-list)
(let ((result (first (unbox a-list))))
(set-box! a-list (rest (unbox a-list)))
result))
```
**clojure:**
Note the in clojure,*pop*only returns the first element; the original list is left unmodified\.
## [Fixed\-Length Arrays](https://hyperpolyglot.org/lisp#fixed-length-arrays)
## vector literal
**racket**
*\#\(1 2 3\)*creates an immutable vect\.*\(vector 1 2 3\)*creates a mutable vector\.
## vector access
## set vector element
**racket**
*vector\-set\!*throws an error if called on an immutable vector\.
## vector to list
## list to vector
## abstract sequence
Lists and vectors support the same operations; the only difference is the speed at which the operations can be performed\. It is a convenience for the developer if functions that perform the operations have the same name; i\.e\. if lists and vectors are members of an abstract sequence type\. Clojure has gone furthest in this direction, making all the customary list functions work on vectors as well\. In common lisp and emacs lisp, some of the list functions also work on vectors, and some don't\. In Scheme none of the list functions work on vectors\.
## sequence data types
The containers that respond to sequence functions\.
## sequence predicate
## list functions usable on sequences
## make\-array
In Lisp terminology, both arrays and vectors refer to collections which are of fixed size; vectors are arrays with rank 1\. Only common lisp supports arrays with rank greater than 1\.
## array access
## set array element
## array dimensions
*array\-rank*returns the number of indices required to specify an element in the array\.*array\-dimensions*returns the size of the array; the number of cells is the product of the elements of the list\.
## range
## list comprehension
## [Dictionaries](https://hyperpolyglot.org/lisp#dictionaries)
Lisp has a tradition of using lists of pairs for dictionaries\. The data structures in this section are implemented using hash tables\.
**racket:**
In addition to hash tables there are a set of functions which work with any dictionary type, which in Racket include hash tables, lists of cons cell pairs, and vectors\. When a vector is treated as a dictionary, the value is an element and the key is the integer index of the element\.
**clojure:**
There are three dictionary types which can be used with the functions described in this section:
constructortype\(hash\-map "t" 1 "f" 0\)clojure\.lang\.PersistentHashMap\(array\-map "t" 1 "f" 0\)clojure\.lang\.PersistentArrayMap\(zipmap '\("t" "f"\) '\(1 0\)\)clojure\.lang\.PersistentArrayMap\(sorted\-map "t" 1 "f" 0\)clojure\.lang\.PersistentTreeMap\(sorted\-map\-by \#\(< %1 %2\) "t" 1 "f" 0\)clojure\.lang\.PersistentTreeMap## [literal](https://hyperpolyglot.org/lisp#dict-literal)
The syntax for a dictionary literal\.
## [constructor](https://hyperpolyglot.org/lisp#dict-ctor)
The constructor for a dictionary\.
**racket:**
The constructors useequal?to test for equality of the two keys\.
There are also constructors which useeq?oreqv?to test keys:hasheq,hasheqv,make\-immutable\-hasheq,make\-immutable\-hasheqv\.
## [predicate](https://hyperpolyglot.org/lisp#dict-pred)
How to test whether a value is a dictionary\.
## [size](https://hyperpolyglot.org/lisp#dict-size)
How to get the number of keys stored in the dictionary\.
## [lookup](https://hyperpolyglot.org/lisp#dict-lookup)
How to look up the value associated with a key\.
## [update](https://hyperpolyglot.org/lisp#dict-update)
How to insert a key\-value pair or replace the value stored with an existing key\.
## [missing key behavior](https://hyperpolyglot.org/lisp#dict-missing-key)
What happens when a lookup is performed on a key not in the dictionary\.
**racket:**
How to handle the error and return a null when the key is not found:
```
(with-handlers ((exn:fail? (lambda (e) null))) (get h "goodbye"))
```
## [is key present](https://hyperpolyglot.org/lisp#dict-is-key-present)
How to check whether a key exists in a dictionary\.
## [delete](https://hyperpolyglot.org/lisp#dict-del)
How to remove a key and its associated value from a dictionary\.
## [merge](https://hyperpolyglot.org/lisp#dict-merge)
How to merge two dictionaries\.
## [invert](https://hyperpolyglot.org/lisp#dict-invert)
How to turn a dictionary into its inverse\. If a key 'foo' is mapped to value 'bar' by a dictionary, then its inverse will map the key 'bar' to the value 'foo'\.
If multiple keys are mapped to the same value in the original dictionary, some of the keys will be discarded in the inverse\.
## [iterate](https://hyperpolyglot.org/lisp#dict-iter)
How to iterate over the key\-value pairs in a dictionary\.
## [keys and values as lists](https://hyperpolyglot.org/lisp#dict-key-val-lists)
How to get the keys or the values in a dictionary as lists\.
## [User\-Defined Types](https://hyperpolyglot.org/lisp#user-defined-types)
## defstruct
## struct
## struct getter
## struct setter
## struct predicate
## [Functions](https://hyperpolyglot.org/lisp#functions)
## let, let\*
Traditionallyletperforms its assignments in parallel andlet\*serially\.
**clojure**
In Clojure,*let*and*let\**are synonyms and both perform serial assignment\.
**emacs**
Note thatletuses dynamic scope\. Uselexical\-letfor lexical scope:
```
ELISP> (let ((x 3)) (defun get-x () x))
get-x
ELISP> (get-x)
*** Eval error *** Symbol's value as variable is void: x
ELISP> (let ((x 4)) (get-x))
4
ELISP> (lexical-let ((x 3)) (defun get-x-2 () x))
get-x-2
ELISP> (get-x-2)
3
ELISP> (lexical-let ((x 4)) (get-x-2))
3
```
## define function
## optional argument
## variable number of arguments
## default value
## named parameter
**common lisp:**
In common lisp, named parameters are optional\. Named values can be assigned default values:
```
(defun logarithm (&key number (base 10)) (/ (log number) (log base)))
```
If a named parameter is not provided at invocation and has not been assigned a default value, then it is set to*nil*\.
**racket:**
[How to Implement Named Parameters in Scheme](http://rosettacode.org/wiki/Named_parameters#Scheme)
**emacs lisp:**
In emacs lisp named parameters are mandatory\. A runtime error results in they are not provided when the function is invoked\.
## tail call optimization
**common lisp:**
The ANSI Common Lisp specification does not require an implementation to perform tail call optimization\.
## [get docstring](https://hyperpolyglot.org/lisp#docstring)
How to get the documentation string for a function\.
**common lisp:**
describereturns the documentation string with additional information such as the function signature\. To get just the documentation string use this:
```
(documentation #'mapcar 'function)
```
## [define function with docstring](https://hyperpolyglot.org/lisp#define-docstring)
How to define a function that has a documentation string\.
## [apropos and documentation search](https://hyperpolyglot.org/lisp#search-doc)
How to search definitions and documentation\.
Apropos takes a pattern and returns all defined symbol names which match the pattern\.
**clojure:**
aproposreturns matching symbol names as a list\.
find\-docsearches all documentation strings and writes any which match to standard out\.
Bothaproposandfind\-doccan take a string or a regular expression as an argument\.
**emacs lisp:**
aproposdisplays the documentation for matching definitions in the\*Apropos\*buffer\. The argument is a string but will be treated as a regular expression\.
## [Execution Control](https://hyperpolyglot.org/lisp#execution-control)
## progn
*progn*and its equivalents in other dialects returns the value of the last expression\. Common Lisp and Emacs Lisp also have*prog1*and*prog2*for returning the value of the 1st or 2nd expression\.
## loop
## do
## dotimes
## if
## when
## [Exceptions](https://hyperpolyglot.org/lisp#exceptions)
## error
## handle error
**racket:**
Calling*error*raises an exception of type exn:fail
**emacs:**
In the example:
```
(condition-case nil (error "failed") (error (message "caught error") nil))
```
the 2nd argument to*condition\-case*is the code which might raise an error, and the 3rd argument is the error handler\. The error handler starts with condition to be caught\. The last*nil*is the return value of the entire*condition\-case*expression\.
An error cannot be handled by catch\. An uncaught throw will generate an error, which can be handled by a condition\-case error handler\.
## define exception
How to define a custom exception with a payload\.
**common lisp:**
The :report clause is not necessary\. If defined it will be displayed if the exception is handled by the lisp debugger\.
## throw exception
**emacs:**
The 1st argument of an emacs*throw*expression identifies the type of exception, and the 2nd argument will be the return value of the*catch*expression that catches the exception\.
## catch exception
**emacs**
The following*catch*expression will return*nil*:
```
(catch 'failed (throw 'failed nil) t)
```
## restart case
## invoke restart
## finally clause
**racket:**
- [Unwind\-protect vs\. Continuations](http://www.nhplace.com/kent/PFAQ/unwind-protect-vs-continuations-original.html)Kent Pitman
- [Unwind\-protect in Portable Scheme](http://www.ccs.neu.edu/home/dorai/uwcallcc/uwcallcc.html)Dorai Sitiram
**clojure:**
Here is an optional technique for making sure that a file handle is closed:
```
(with-open [#^PrintWriter w (writer f)] (.print w content))
```
## lazy evaluation
## continuations
## [Streams](https://hyperpolyglot.org/lisp#streams)
## [standard file handles](https://hyperpolyglot.org/lisp#std-file-handles)
## [end\-of\-file behavior](https://hyperpolyglot.org/lisp#eof)
## [read line from stdin](https://hyperpolyglot.org/lisp#read-stdin)
## [chomp](https://hyperpolyglot.org/lisp#chomp)
## [write line to stdout](https://hyperpolyglot.org/lisp#println)
## [write formatted string to stdout](https://hyperpolyglot.org/lisp#format-stdout)
**racket**
*printf*prints to stdout\.*format*returns a string\.
**emacs lisp**
The*format*statement returns the generated string\. When used for i/o, it prints in the emacs minibuffer\.
## [open file for reading](https://hyperpolyglot.org/lisp#open-file)
## [open file for writing](https://hyperpolyglot.org/lisp#open-file-write)
## [open file for appending](https://hyperpolyglot.org/lisp#open-file-append)
## [close file](https://hyperpolyglot.org/lisp#close-file)
## [close file implicitly](https://hyperpolyglot.org/lisp#close-file-implicitly)
## [read line](https://hyperpolyglot.org/lisp#read-line)
## [iterate over file by line](https://hyperpolyglot.org/lisp#iterate-file)
## [read file into array of strings](https://hyperpolyglot.org/lisp#read-file-array)
## [read file into string](https://hyperpolyglot.org/lisp#read-file-str)
## [write string](https://hyperpolyglot.org/lisp#write-str)
## [write line](https://hyperpolyglot.org/lisp#write-line)
## [flush filehandle](https://hyperpolyglot.org/lisp#flush-file)
## [Emacs Buffers](https://hyperpolyglot.org/lisp#emacs-buffers)
## [Files](https://hyperpolyglot.org/lisp#files)
## [file test, regular file test](https://hyperpolyglot.org/lisp#file-test)
## [file size](https://hyperpolyglot.org/lisp#file-size)
## [is file readable, writable, executable](https://hyperpolyglot.org/lisp#file-readable-writable-executable)
## [set file permissions](https://hyperpolyglot.org/lisp#chmod)
## [copy file, remove file, rename file](https://hyperpolyglot.org/lisp#cp-rm-mv)
## [create symlink, symlink test, get target](https://hyperpolyglot.org/lisp#symlink)
## [temporary file](https://hyperpolyglot.org/lisp#tmp-file)
## [in memory file](https://hyperpolyglot.org/lisp#in-memory-file)
## [Directories](https://hyperpolyglot.org/lisp#directories)
## [build pathname](https://hyperpolyglot.org/lisp#build-pathname)
How to build a file pathname from components\.
## [dirname and basename](https://hyperpolyglot.org/lisp#dirname-basename)
How to extract the directory portion of a pathname; how to extract the non\-directory portion\.
## [absolute pathname](https://hyperpolyglot.org/lisp#abs-pathname)
How to get the get the absolute pathname for a pathname\. If the pathname is relative the current working directory will be appended\.
## [iterate over a directory by file](https://hyperpolyglot.org/lisp#iterate-dir)
How to iterate over the files in a directory\.
## [make directory](https://hyperpolyglot.org/lisp#mkdir)
How to create a directory, including any parents directories specified in the path\.
## [recursive copy](https://hyperpolyglot.org/lisp#recursive-cp)
How to copy a directory and its contents\.
## [remove empty directory](https://hyperpolyglot.org/lisp#rmdir)
How to remove an empty directory\.
## [remove directory and its contents](https://hyperpolyglot.org/lisp#rm-rf)
How to remove a directory and its contents\.
## [directory test](https://hyperpolyglot.org/lisp#dir-test)
How to test whether a directory exists\.
## [Processes and Environment](https://hyperpolyglot.org/lisp#processes-environment)
## external command
## command line arguments
**emacs**
The global variables*command\-line\-args*and*argv*are set when emacs is run in shebang mode: i\.e\. with the —script option\.*command\-line\-args*contains the pathname used to invoke emacs, as well as any options processed by emacs at startup, in addition to any additional arguments\.*argv*only contains the additional arguments\.
## environment variables
## [Libraries and Namespaces](https://hyperpolyglot.org/lisp#libraries-namespaces)
## loading a file
How to load a file and evaluate the top level expressions\.
**common lisp**
Does not display the result of any evaluations\.
**racket**
Displays the result of the last evaluation\.
## loading a library
## [Objects](https://hyperpolyglot.org/lisp#objects)
## define class
## make instance
## read attribute
## write attribute
## define method
## invoke method
## define subclass
## universal superclass
## multiple inheritance
## [Lisp Macros](https://hyperpolyglot.org/lisp#lisp-macros)
## backquote and comma
## defmacro
## defmacro\-backquote
## macro predicate
## macroexpand
*macroexpand*recursively expands a sexp until the head is no longer a macro\. It does not expand arguments that are macros\.
**common lisp**
Common lisp also has*macroexpand\-1*, which will non\-recursively expand a macro once\. The head of the expansion may thus be a macro\.
**clojure**
Clojure also has*macroexpand\-1*\. See above for an example of use\.
**emacs lisp**
Emacs has*macroexpand\-all*, which will recursively expand a sexp until head and arguments are free of macros\.
## splice quote
## recursive macro
## hygienic
Does the language have macros whose expansions are guaranteed not to introduce name collisions\.
## local values
## [Reflection](https://hyperpolyglot.org/lisp#reflection)
## type\-of
How to get the data type of the entity referred to by a symbol\.
## [Java Interoperation](https://hyperpolyglot.org/lisp#java-interop)
## version used on jvm
## extra libraries used
**racket:**
The srfi\-1 library brings in a common list functions which Kawa does not make available by default\. See[SRFI](http://srfi.schemers.org/srfi-1/srfi-1.html)\.
## new
## method
## class method
## chain
## import
## to java array
[ANSI Specification](http://www.lispworks.com/documentation/HyperSpec/Front/) [SBCL User Manual](http://www.sbcl.org/manual/) [Quicklisp](http://www.quicklisp.org/beta/)
For a package manager we use Quicklisp\. Here is how to install it and use it to load thecl\-ppcrelibrary:
```
$ curl -O http://beta.quicklisp.org/quicklisp.lisp
$ sbcl
* (load "quicklisp.lisp")
* (quicklisp-quickstart:install)
* (ql:quickload "cl-ppcre")
* (cl-ppcre:all-matches "foo" "foo bar")
```
Quicklisp creates aquicklispdirectory in the user's home directory\. Once quicklisp is downloaded and installed, it can be used like this:
```
$ sbcl
* (load "~/quicklisp/setup.lisp")
* (ql:quickload "cl-ppcre")
* (cl-ppcre:all-matches "foo" "foo bar")
```
One can ensure that Quicklisp is automatically loaded at startup by putting the load command into the\.sbclrcfile:
```
$ cat ~/.sbclrc
(load "~/quicklisp/setup.lisp")
```
## [Racket](https://hyperpolyglot.org/lisp#top)
[Guide: Racket](http://docs.racket-lang.org/guide/index.html) [Reference: Racket](http://docs.racket-lang.org/reference/index.html) [PLaneT: Racket Packages](http://planet.racket-lang.org/)
Racket ships with a large number of libraries in thecollectsdirectory of the installation which can be loaded with therequirecommand, which takes a raw symbol which is the relative pathname from thecollectsdirectory to the file, not including the\.rktsuffix\. The Racket 5\.1 distribution includes 50 SRFI libraries\.
Racket also has a built in package management system\. Browse the[list of available packages](http://planet.racket-lang.org/)\. To install a package, click through to the detail page for the package and get therequirestring to load it\. If therequirestring is executed by Racket, the library will be downloaded somewhere in the user's home directory\. When I ran this on my Mac
```
$ racket
> (require (planet "spgsql.rkt" ("schematics" "spgsql.plt" 2 3)))
```
the files for the PostgreSQL database bindings were installed in~/Library/Racket\.
## [Clojure](https://hyperpolyglot.org/lisp#top)
[Clojure Reference](http://clojure.org/Reference) [Clojure Cheat Sheet](http://clojure.org/cheatsheet)
## Calling Java
Here are the basics of calling Java code:
```
(def rnd (new java.util.Random)) ; create Java object
(. rnd nextFloat) ; invoke method on object
(. rnd nextInt 10) ; invoke method with argument
(. Math PI) ; static member
(import '(java.util Random)) ; import
```
Clojure automatically imports everything in java\.lang\.
There are shortcuts for the above syntax:
```
(Random.)
(new Random)
Math/PI
(. Math PI)
(.nextInt rnd)
(. rnd nextInt)
```
Because they are primitive types and not objects, Clojure provides functions specific to Java arrays:
```
(make-array CLASS LEN)
(make-array CLASS DIM & DIMS)
(aset ARY IDX VAL)
(aset ARY IDX_DIM1 IDX_DIM2 ... VAL)
(aget ARY IDX)
(aget ARY IDX_DIM1 IDX_DIM2 ...)
(alength JARY)
(to-array SEQ)
(into-array TYPE SEQ)
(amap ARY I COPY EXPR)
(areduce ARY IDX COPY INIT EXPR )
```
## [Emacs Lisp](https://hyperpolyglot.org/lisp#top)
[GNU Emacs Manual](http://www.gnu.org/software/emacs/manual/html_mono/emacs.html) [GNU Emacs Lisp Reference Manual](http://www.gnu.org/software/emacs/manual/html_mono/elisp.html)
To get an introduction to Emacs Lisp Programming from within Emacs use
RunM\-x lisp\-interaction\-modeto put Emacs in lisp interaction mode\. In lisp interaction mode the commandC\-x ewill evaluate the s\-expression on the current line\.M\-x eval\-bufferwill evaluate the entire buffer\.
Use lisp interaction mode to define functions which can be called from Emacs\. The following defines a function calleddired\-emacs\-lispfor browsing the Emacs Lisp directory:
```
(defun dired-emacs-lisp ()
"Open the Emacs Lisp directory in dired."
(interactive)
(dired "/Applications/Emacs.app/Contents/Resources/lisp"))
```
The directory is hard\-coded into the function and may be different on your system\. Once defined the function can be invoked withM\-x dired\-emacs\-lisp\. Not all Lisp functions can be called in this manner\. Those that can are called*commands*\. The body of a command has an optional documentation string, followed by a call tointeractive, followed by the code which executes when the command is invoked\. The documentation string can be accessed from Emacs by runningM\-x describe\-functionand entering the name of the function when prompted\.
The call tointeractiveis what makes a Lisp function a command\. It can takes optional arguments\. UseM\-x describe\-functiononinteractiveto see a description of these arguments\.
To bind the command to the keyC\-c lrun the following in Lisp interaction mode:
```
(global-set-key "\C-cl" 'dired-emacs-lisp)
```
If it is desired to have the above command and key binding always available when Emacs starts up, put them in~/\.emacs\.d/init\.el\.
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