Or you can always use eval. ((eval res (interaction-environment)))
Sorry... I was watching "The Most Beautiful Program Ever Written" talk from W. Byrd and got too excited :-D Aleix On Fri, Mar 5, 2021 at 4:30 PM Olivier Dion via General Guile related discussions <guile-user@gnu.org> wrote: > > On Fri, 05 Mar 2021, Tim Meehan <btmee...@gmail.com> wrote: > > I wanted to store a thunk in a hashtable so that I could look up its key > > and then run it later. Something like this: > > > > #! /usr/bin/guile > > !# > > > > (use-modules (ice-9 hash-table)) > > > > (define stuff (alist->hash-table > > '((a . (lambda () (display "event a\n"))) > > (b . (lambda () (display "event b\n"))) > > (c . (lambda () (display "event c\n")))))) > > You've quoted the whole s-exp. Which means lambda is never applied. > You have to apply lambda in order to create a procedure. > > > > > (define res (hash-ref stuff 'a)) > > (res) > > > > But when I run it: > > Wrong type to apply: (lambda () (display "event a\n")) > > You're trying to apply a list and not a procedure. This is because of > the quote mentioned above. In other words, you're doing this: > ---------------------------------------------------------------------- > (apply '(lambda () (display "event a\n"))) > ---------------------------------------------------------------------- > > Change the ' for ` and unquote the lambdas with ,. Like this: > ---------------------------------------------------------------------- > (define stuff (alist->hash-table > `((a . ,(lambda () (display "event a\n"))) > (b . ,(lambda () (display "event b\n"))) > (c . ,(lambda () (display "event c\n")))))) > ---------------------------------------------------------------------- > > Or use the list procedure instead of quoting: > ---------------------------------------------------------------------- > #! /usr/bin/guile > !# > > (use-modules (ice-9 hash-table)) > > (define stuff (alist->hash-table > (list (cons 'a (lambda () (display "event a\n"))) > (cons 'b (lambda () (display "event b\n"))) > (cons 'c (lambda () (display "event c\n")))))) > > (define res (hash-ref stuff 'a)) > (res) > ---------------------------------------------------------------------- > > -- > Olivier Dion > PolyMtl >
