On Mon, Apr 22, 2019 at 08:57:32PM +0200, Zelphir Kaltstahl wrote:
> Hello Guile users,
>
> I was looking for an assert facility in Guile and found the following:
>
> https://www.gnu.org/software/guile/manual/html_node/rnrs-base.html#rnrs-base
>
> (Search for assert there to find it on the page.)
>
> However, while searching, I also found something that looks even better:
>
> http://okmij.org/ftp/Scheme/assert-syntax-rule.txt
This is my assert macro. I'm sure there are dozens of other versions.
---
(define-module (mlg assert)
#:export (assert
assert-type))
(define-syntax __FILE__
(syntax-rules ()
((_)
(or (assv-ref (current-source-location) 'filename)
"(unknown file)"))))
(define-syntax __LINE__
(syntax-rules ()
((_)
(or (assv-ref (current-source-location) 'line)
"(unknown line)"))))
(define-syntax assert
(lambda (x)
(syntax-case x ()
((_ expression)
#'(let ((ret expression))
(unless ret
(error
(format #f "~a:~a: assertion failed: ~a = ~s"
(__FILE__) (__LINE__) 'expression expression))))))))
(define-syntax assert-type
(lambda (x)
(syntax-case x ()
[(_ type var)
#`(if (not (#,(datum->syntax #'var
(string->symbol (string-append
(symbol->string
(syntax->datum #`type))
"?")))
var))
(scm-error 'wrong-type-arg
#f
(string-append "not type '"
#,(symbol->string (syntax->datum #`type))
"': ~s")
(list var)
(list var)))])))
