Re: Contract programming in Guile

[Linus Björnstam]

I wrote this a billion million years ago: 
https://hg.sr.ht/~bjoli/misc/browse/contract.scm?rev=tip

Very basic. Contracts are just syntax and not first-class objects. 

-- 
  Linus Björnstam

On Sat, 17 Jul 2021, at 18:01, Olivier Dion via General Guile related 
discussions wrote:
> Hi all,
> 
> I'm a big fan of contract programming and was wondering if there's any
> SRFI or library that offers this in Guile?
> 
> Here's an example of what I mean by contract:
> --------------------------------------------------------------------------------
> ;; Given
> (define (sum x y z)
> 
>   "Return the sum of X, Y and Z."
> 
>   (#:pre-conditions
>    (>= x 0)
>    (>= y 0)
>    (>= z 0))
> 
>   (#:post-conditions
>    (>= result 0))
> 
>   (+ x y z))
> 
> ;; Would expand to something like
> (use-modules (ice-9 local-eval))
> 
> (define (sum x y z)
> 
>   "
>   Return the sum of X, Y, and Z.
>   
>   pre-conditions:
>       (>= x 0)
>         (>= y 0)
>         (>= z 0)
>         
>    post-conditions:
>         (>= result 0)
>   "
> 
>   (for-each (lambda (condition)
>               (unless (local-eval condition (the-environment))
>                 (begin
>                   (format #t "Failed pre-condition: ~a\n" condition)
>                   (exit 1))))
>             '((>= x 0)
>               (>= y 0)
>               (>= z 0)))
> 
>   (let ((result (begin (+ x y z))))
>     (for-each (lambda (condition)
>                 (unless (local-eval condition (the-environment))
>                   (begin
>                     (format #t "Failed post-condition: ~a\n" condition)
>                     (exit 1))))
>               '((>= result 0)))
>     result))
> --------------------------------------------------------------------------------
> 
> -- 
> Olivier Dion
> PolyMtl
> 
>