I have a list containing letters. When I do (car '(a)) it gives me the symbol a. How do I compare it to the characte开发者_如何学Pythonr a?
Must I do (eq? (car list) (car '(a))?
Symbols and characters are different kinds of data. Fortunately, Scheme is willing to let you convert nearly anything you want. In Racket, for instance:
#lang racket
;; the symbol a:
'a
;; the character a:
#\a
;; are they equal? no.
(equal? 'a #\a) ;; produces #f
;; converting a character to a symbol:
(define (char->symbol ch)
(string->symbol (string ch)))
(char->symbol #\a) ;;=> produces 'a
;; converting a symbol to a character
(define (symbol->char sym)
(match (string->list (symbol->string sym))
[(list ch) ch]
[other (error 'symbol->char
"expected a one-character symbol, got: ~s" sym)]))
(symbol->char 'a) ;; => produces #\a
With all that said, if you're working on a homework assignment, the instructor almost certainly has an easier path in mind for you.
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