CODEWITHSUNDEEP
stringclojurecharacter
imranolas
imranolas

Reputation: 520

Clojure: character literal equality

I presumed, somewhat naively perhaps, that single character strings in Clojure would be equal regardless of how they were generated.

(= "G" "G")
=>
true

(= "G" \G)
=>
false

(= \G \G)
=>
true

Turns out not to be the case. Can anyone explain why?

Upvotes: 3

Views: 1195

Answers (2)

ez121sl
ez121sl

Reputation: 2429

Just for the sake of completeness... ClojureScript, unlike Clojure, behaves exactly as the OP presumed. Since Javascript does not have the character type, just String, ClojureScript characters are implemented as single-character strings.

In ClojureScript REPL:

(= "G" "G")
;=> true

(= "G" \G)
;=> true

(= \G \G)
;=> true

(type "G")
;=> #object[String "function String() {
;=>    [native code]
;=> }"]

(type \G)
;=> #object[String "function String() {
;=>    [native code]
;=> }"]

Upvotes: 5

Sam Estep
Sam Estep

Reputation: 13324

A character is not the same as a single-character string. Rather, a single-character string can be thought of as a sequence whose first and only item is a character.

(type "G")
;=> java.lang.String
(type \G)
;=> java.lang.Character

(count "G")
;=> 1
(count \G)
;=> UnsupportedOperationException count not supported on this type: Character

(seq "G")
;=> (\G)
(seq \G)
;=> IllegalArgumentException Don't know how to create ISeq from: java.lang.Character

(first "G")
;=> \G
(first \G)
;=> IllegalArgumentException Don't know how to create ISeq from: java.lang.Character

Upvotes: 5

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