Re: Arbitrary function: find the number(s) of expected arguments

[Clément Pit--Claudel]

Drew, your message is actually much harder to read in Thunderbird that the one 
you replied to. Maybe using a plain text response in such cases would be best? 
I had no trouble reading Paul's email, but yours was tricky.

On 03/25/2016 02:19 PM, Drew Adams wrote:
> (Please use plain-text for this mailing list from now on. I won't bother 
> trying to convert the formatting this time.)
> 
>  
> 
>> IIUC, you _cannot_ use `func-arity' to test whether something
> 
>> is a subr.
> 
> Yes, but you can and should use `subrp' for that.
> 
> Of course you can. But that's irrelevant here. This is about what 
> `subr-arity' does. Its behavior is not the same as `func-arity' for a 
> non-subr. If we are not deprecating `subr-arity' then it is not enough to 
> send users to the doc for `func-arity'.
> 
>> IOW, I am repeating the same argument I made before, when
> 
>> I said that `subr-arity' should not be deprecated and
> 
>> simply replaced by `func-arity'.
> 
> I understood it as argument against aliasing `subr-arity' to
> 
> the new function: this can break _existing_ code if it relies
> 
> on the fact that `subr-arity' signals an error when called with
> 
> anything, but builtin.
> 
> Yes. And?
> 
> The same argument applies to just having its doc string tell users to use 
> `func-arity'. That might not break existing code, but it breaks the doc 
> string. It no longer says what function `subr-arity' does. And it gives the 
> false impression that `func-arity' does the same thing. In fact, `func-arity' 
> does something /different/ if the arg is not a subr.
> 
>> This is a step backward.  Unless we are really deprecating
> 
>> and replacing it, we should document `subr-arity' properly,
> 
>> as before, with the addition of cross-ref to see `func-arity',
> 
>> stating that it handles any type of function.
> 
> I personally don't see why we need two functions for this.
> 
> So, I would deprecate `subr-arity', but keep it around for
> 
> backward compatibility.
> 
> I personally feel the opposite - see my argument about not breaking existing 
> code. But if that will be the decision then that's different. So far, there 
> has been no decision to deprecate `subr-arity', AFAIK.
> 
> On the other hand, I don't really care. All I want is that there
> 
> is `func-arity' that works for _any_ function. I'm not attached
> 
> to anything in the patch and as long as `func-arity' works,
> 
> `func-arity' works for any function. So your want is satisfied.
> 
> However, obtaining your want at the expense of also breaking a doc string is 
> not right.
> 
> feel free to change anything.
> 
> I'm not going to change the broken doc string. But I certainly hope that 
> someone will.
> 
> When code is improved, if that change entails needing to change the doc, then 
> the doc should be updated appropriately.
>

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