Hi Tomas! Ultimately I need the minimum and maximum arity of functions (not sure if anything in between is needed, but I think not). Minimum and knowing, that rest arguments exist is not sufficient. The exact maximum number of arguments is what I require, even if it turns out to be infinity or some implementation limit.
Trying to give an example: It is a learning project, about function combinators and there are combinators, which could for example return functions, which split their arguments into 2 groups of arguments, 1 group for each combined function. Lets say the combined function h takes k, k+1 or k+2 arguments. Out of k arguments the first function (f) of the combined functions could take n arguments leaving k-n arguments for the second function (g). However, if k+1 arguments were provided to h or k+2 arguments, then then the second function (g) could take k-n+1 or k-n+2 arguments, simply because more arguments are remaining for the second function. To implement checks for correct number of arguments at runtime (assertions), I need, I think, the exact maximum number of arguments and not only the information, that there can be rest arguments. The reference manual has more about "program arities" (https://www.gnu.org/software/guile/manual/guile.html#Compiled-Procedures <https://www.gnu.org/software/guile/manual/guile.html#Compiled-Procedures>), but that API is not working currently, as found out in a previous thread on this mailing list: https://lists.gnu.org/archive/html/guile-user/2021-05/msg00044.html <https://lists.gnu.org/archive/html/guile-user/2021-05/msg00044.html>. I think only the one function you mention is currently working. While that API is not properly working, I think "callable objects" could be a solution to my problem. Thanks for your reply! Zelphir On 8/14/21 8:53 AM, to...@tuxteam.de wrote: > 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 -- repositories: https://notabug.org/ZelphirKaltstahl
