Elisp: String Comparison, Equality, Order

Equality Test

string-equal

For comparing

• Two Strings
• Two Symbols
• A string and a symbol

;; dedicated function for comparing string
(string-equal "abc" "abc") ;  t

;; string case matters
(string-equal "abc" "Abc") ;  nil

;; can be used to compare two symbols
(string-equal 'abc 'abc) ;  t

;; can be used to compare string and symbol
(string-equal "abc" 'abc) ;  t

string-equal-ignore-case

like string-equal but Case-Insensitive.

new in Emacs 29 (Released 2023-07)

compare-strings

(compare-strings STR1 START1 END1 STR2 START2 END2 &optional IGNORE-CASE)

test substring equality, and optionally ignore case.

(compare-strings "xx3" 0 2 "xx4" 0 2)
;; t

string-collate-equalp

(string-collate-equalp S1 S2 &optional LOCALE IGNORE-CASE)

test string equality but consider similar character as equivalent. e.g. the unicode ligature char fi is considered equal to character sequence fi.

(string-collate-equalp "fi"  "fi")
;; t

;; fi
;; name: LATIN SMALL LIGATURE FI
;; codepoint 64257

String Comparison

• string-greaterp
• string-collate-lessp
• string-version-lessp
• string-prefix-p
• string-suffix-p

• string-distance