Thank you. This works just fine in any place, where function is expected. But the case with "case" still doesn't work
(case 5 [((hash-dot (+ 2 3))) 1] [else 2]) => 2 I think, that I need to do something with the Racket reader. Понедельник, 29 июля 2013, 13:53 -04:00 от Vincent St-Amour <[email protected]>: >Here's a quick solution: > > #lang racket > > (define-syntax-rule (hash-dot e) > (let-syntax ([computed-e (lambda (stx) (datum->syntax #'e e))]) > (computed-e))) > > (hash-dot (+ 2 3)) > > >This defines a local macro that computes the value of `e' at compile >time. Any binding that you use in `e' will need to be bound at syntax >time (which, in #lang racket, is all of racket/base), which may mean >using `(require (for-syntax X))'. > >If you try to compute, say, a function at compile-time, you'll run into >trouble, though. > >Vincent > > > >At Mon, 29 Jul 2013 06:25:21 +0400, >Roman Klochkov wrote: >> >> [1 <multipart/alternative (7bit)>] >> [1.1 <text/plain; utf-8 (base64)>] >> Is there simple way to calculate during compilation. Something like #. in >> Common Lisp. >> >> For example how to do something like >> (case ftype >> ((#.(keyword->g-type 'enum) >> #.(keyword->g-type 'flags)) >> (convert-to-foreign value (g-type->lisp type))) >> (#.(keyword->g-type 'double) >> (coerce value 'double-float)) >> (#.(keyword->g-type 'float) >> (coerce value 'single-float)) >> ((#.(keyword->g-type 'int) >> #.(keyword->g-type 'uint) >> #.(keyword->g-type 'long) >> #.(keyword->g-type 'ulong) >> #.(keyword->g-type 'int64) >> #.(keyword->g-type 'uint64)) >> (round value)) >> (else value)) >> >> >> >> where keyword->g-type is a function (-> symbol? exact-integer?). >> >> I don't want to place resulting numbers, because then there will be a lot of >> "magic numbers" corresponfing to different foreign types. >> >> >> -- >> Roman Klochkov >> [1.2 <text/html; utf-8 (base64)>] >> >> [2 <text/plain; us-ascii (7bit)>] >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users -- Roman Klochkov
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