Your comment says that y-or-n? returns either #t or #f. I see the line where you return #t. Where do you return #f?
Justin On Dec 30, 2013 4:04 PM, "亀田馬志" <masashi.kam...@gmail.com> wrote: > Hello. > > I think I understand how memq, memv, member works: > > > (memq 'y '(y yes n no)) > '(y yes n no) > > (memq 'n '(y yes n no)) > '(n no) > > (memq 'racket '(y yes n no)) > #f > > > > By the way, I wrote a procedure as follows: > > (require srfi/13) > > (define (yes-or-no? arg) > ; expected it returns #t or #f > ; depending on input such as yes or no > (letrec ((y-or-n? > ; if argument is either Y or YES, > ; it returns #t otherwise #f > (lambda (sym) > (and (memq sym '(Y YES)) #t))) > (symbol-upcase > ; confirm any symbol into uppercase > (lambda (arg) > (if (symbol? arg) > (string->symbol (string-upcase (symbol->string arg))) > (yes-or-no? (read)))))) > (let ((sym (symbol-upcase arg))) > (if (memq sym '(Y YES N NO)) > (y-or-n? sym) > (yes-or-no? (read)))))) > > I expected that (cond ((I input y or yes) returns #t) > ((I input n or no) returns #f) > (else this procedure waits something)) > > However, result is sooooo strange: > > > (yes-or-no? (read)) > 3 > 2 > 4 > foo > bar > baz > yes > y > no > n > #f > > Notice that even though yes, y or no is entered, the procedure ignores and > it never returns #f until n is entered. > Strange. > Does anyone know why this doesn't work? > > Thanks. > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > >
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