Re: Applicable structs and vtables

[<tomas@tuxteam.de>]

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On Fri, Aug 13, 2021 at 08:33:33PM +0000, Zelphir Kaltstahl wrote:
> Hi Guile users,
> 
> I have some code, in which I wrap procedures in a record, which contains
> members, which express the arity of the procedures. For example one struct be:
> 
> <arity-function: min: 1, max: 3, function: (some lambda here)>

I don't know whether what you're after is about generalising what a
function can be ("callable objects" or similar), or if procedure
arity introspection at run time is your ultimate goal.

In the second case, there is `procedure-minimum-arity', which might
already cater to your wishes :-)

  (procedure-minimum-arity cons) ; takes two arguments, no "rest"
  => (2 0 #f)
  (procedure-minimum-arity +) ; takes at least 0, takes "rest"
  => (0 2 #t)
  (let ((foo (lambda (x y . z) ('some-result)))) ; DIY
    (procedure-minimum-arity foo))               ; at least 2, with "rest"
  => (2 0 #t)

I don't know (yet) what the middle number is for, though ;-)

Cheers
 - t

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