On Thu, Jul 9, 2020 at 10:32 AM Sorawee Porncharoenwase < sorawee.pw...@gmail.com> wrote:
> Racket REPL doesn’t handle unicode well. If you try (regexp-match? > #px"^[a-zA-Z]+$" "héllo") in DrRacket, or write it as a program in a file > and run it, you will find that it does evaluate to #f. > See this issue for workarounds, including installing the `readline-gpl` package: https://github.com/racket/racket/issues/3223 But you may have some other issues: for me, `(regexp-match? #px"^[a-zA-Z]+$" "h\U+FFC3\U+FFA9llo")` gives an error saying "read-syntax: no hex digit following `\U`" For the original question: > On Thu, Jul 9, 2020 at 7:19 AM Peter W A Wood <peterwaw...@gmail.com> > wrote: > >> I was experimenting with regular expressions to try to emulate the Python >> isalpha() String method. >> > You'd want to benchmark, but, for this purpose, I have a hunch you might get better performance by using `in-string` with a `for/and` loop (which can use unsafe operations internally)—probably especially so if you were content to just test `char-alphabetic?`, which follows Unicode's definition of "alphabetic" rather that Python's idiosyncratic one. Here's an example: #lang racket > > (module+ test > (require rackunit)) > > (define (char-letter? ch) > ;; not the same as `char-alphabetic?`: see > ;; https://docs.python.org/3/library/stdtypes.html#str.isalpha > (case (char-general-category ch) > [(lm lt lu ll lo) #t] > [else #f])) > > (define (string-is-alpha? str) > (for/and ([ch (in-string str)]) > (char-letter? ch))) > > (module+ test > (check-true (string-is-alpha? "hello")) > (check-false (string-is-alpha? "h1llo")) > (check-true (string-is-alpha? "héllo"))) > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAH3z3gYfZqGe5hQheAsSxdX8VzAsGYhi61W5ZpmMkkaRb0F%2B5A%40mail.gmail.com.
