Re: pcase defuns

[Tassilo Horn]

Andrew Hyatt <ahyatt@gmail.com> writes:

Hi Andrew,

> As a part of a personal project, I wrote a way to define functions in
> an equivalent way to pcases.  For example:
>
> (pcase-defun mytest (a b _)
>  "Match on 'a 'b with the third argument a wildcard"
>  "a b match")
>
> (pcase-defun mytest (c ,var _)
>  "Match on 'c binding VAR, with the third argument a wildcard"
>  (format "c %s match" var) )
>
> (mytest 'a 'b 'c) -> "a b match"
> (mytest 'c 100 'c) -> "c 100 match"

So that's basically similar to cl-defgeneric / cl-defmethod just with
pcase pattern matching, right?

In that case, I think I like the cl approach better, i.e., having a
separate definition for the signature + several implementations for
variants.

But since the order of patterns is very significant, I'm not sure if
it's a good idea to specify them separately.  E.g., what if there are
pcase-defun's for mytest in several files?  Then you might get different
behavior depending on the order how files are loaded.  And even in the
"all patterns in mytest.el" case: what if I re-evaluate some
pcase-defuns after the file has been loaded?

So probably I'd favor a pcase-defun which specifies all patterns and
bodies in a single definition, e.g., like:

(pase-defun mytest
  "Docstring"
 ((a b _)
  "a b match")
 ((c ,var _)
  (format "c %s match" var)))

Bye,
Tassilo