Re: define-typed: checking values on proc entry and exit

On 10.05.24 15:47, Dr. Arne Babenhauserheide wrote:
> Hi,
>
> in #guile on IRC¹, old talked about Typed Racket so I thought whether
> that could be done with define-syntax-rule. So I created define-typed.
> This is also on my website², but I wanted to share and discuss it here.
>
> I follow the format by [sph-sc], a Scheme to C compiler. It declares
> types after the function definition like this:
>
> ┌────
> │ (define (hello typed-world) (string? string?)
> │   typed-world)
> └────
>
> ┌────
> │ (define-syntax-rule (define-typed (procname args ...) (ret? types ...) body ...)
> │   (begin
> │     (define (procname args ...)
> │       ;; define a helper pro
> │       (define (helper)
> │         body ...)
> │       ;; use a typecheck prefix for the arguments
> │       (map (λ (type? argument)
> │              (unless (type? argument)
> │                (error "type error ~a ~a" type? argument)))
> │            (list types ...) (list args ...) )
> │       ;; get the result
> │       (let ((res (helper)))
> │         ;; typecheck the result
> │         (unless (ret? res)
> │           (error "type error: return value ~a does not match ~a"
> │                  res ret?))
> │         ;; return the result
> │         res))
> │     ;; add procedure properties
> │     (let ((helper (lambda (args ...) body ...)))
> │       (set-procedure-properties! procname (procedure-properties helper))
> │       ;; preserve the name
> │       (set-procedure-property! procname 'name 'procname))))
> └────
>
> This supports most features of regular define like docstrings, procedure
> properties, and so forth.
>
> ┌────
> │ (define-typed (hello typed-world) (string? string?)
> │   typed-world)
> │ (hello "typed")
> │ ;; => "typed"
> │ (hello 1337)
> │ ;; => type error ~a ~a #<procedure string? (_)> 1337
> │ (define-typed (hello typed-world) (string? string?)
> │   "typed"
> │   #((props))
> │   typed-world)
> │ (procedure-properties hello)
> │ ;; => ((name . hello) (documentation . "typed") (props))
> └────
>
> This should automate some of the guards of [Optimizing Guile Scheme], so
> the compiler can optimize more (i.e. if you check for `real?') but keep
> in mind that these checks are not free: only typecheck outside tight
> loops.
>
> They provide a type boundary instead of forcing explicit static typing.
>
> Also you can do more advanced checks by providing your own test
> procedures and validating your API more elegantly, but these then won’t
> help the compiler produce faster code.
>
> But keep in mind that this does not actually provide static program
> analysis like while-you-write type checks. It’s simply [syntactic sugar]
> for a boundary through which only allowed values can pass. Thanks to
> program flow analysis by the just-in-time compiler, it can make your
> code faster, but that’s not guaranteed. It may be useful for your next
> API definition.
>
> My question now: do you have an idea for a better name than
> define-typed?
>
>
> [sph-sc] <https://github.com/sph-mn/sph-sc>
>
> [Optimizing Guile Scheme]
> <https://dthompson.us/posts/optimizing-guile-scheme.html>
>
> [syntactic sugar]
> <http://www.phyast.pitt.edu/~micheles/scheme/scheme12.html#are-macros-just-syntactic-sugar>
>
>
> ¹ https://web.libera.chat/?nick=Wisp|?#guile
> ² https://www.draketo.de/software/guile-snippets#define-typed
>
>
> Best wishes,
> Arne

Hello Arne,

You might also be interested in my repository for function contracts using CK 
macros:

https://codeberg.org/ZelphirKaltstahl/guile-examples/src/commit/0e231c289596cb4c445efb30168105914a8539a5/macros/contracts

I hope I can check out your macro soon and hope to be able to understand it : )

Regards,
Zelphir

-- 
repositories: https://notabug.org/ZelphirKaltstahl