Re: pcase defuns

[Richard Stallman <rms@gnu.org>]

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  > The way I look at it, it does do this, but it's just structured 
  > differently. The normal defun as one arglist. Mine has one per 
  > matching clause, which means that it can take a variety of 
  > different arguments, all matching. And the arglist and the 
  > matching clauses are the same thing, so the arglist can be (n), or 
  > ('foo n), or (1 2 (3 n)), etc.  Yes, it's weird, but I think the 
  > differentiation here is useful, see my next point.

The argument list is not just a concept in users' minds.
The command C-h f, which shows documentation for a function,
displays the function's argument list.  If you try C-h f cons RET,
you'll see what I mean.

See also `func-arity'.

So there is a practical reason for defining constructs to
set up the function's argument list.

  > In particular, with your 
  > proposal, we lose the ability to have fairly different arg 
  > patterns, with different numbers of args, or different 
  > destructuring patterns.

Not necessarily.  You could specify `&rest args' for an arglist that
conveys no information.  But users find it useful to see in a simple
way what the arguments of the function should be.


-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)