Re: Installing cond* in core

[Stefan Monnier <monnier@iro.umontreal.ca>]

>   > I think the question is rather: why should we have two equivalent and
>   > almost identical matching syntaxes and implementations?
> That is the easiest way to make cond* function.

Only if you consider "easiest" at each small incremental step.
The overall cost of what you've done is already much higher :-)

> I do not understand the pcase code for implementing pattern matching,

You don't need to understand it.

> A priori, I suspect it won't fit.  cond*-subpat, which does this job
> in cond*, passes data up and down the recursion.  I can't tell whether
> pcase does something comparable.  Also, cond*-subpat does not generate
> the overall structure of a clause -- its caller, cond*-match, does
> that.

Throw away cond*-subpat.  Just rewrite

    (cond*
     ((match* PAT FORM) THEN)
     . ELSE)

into something like

    (pcase FORM
      (PAT THEN)
      (_ (cond* . ELSE)))

And presumably for

    (cond*
     ((match* PAT FORM))
     . REST)

you'd rewrite it to

    (pcase-let ((PATH FORM))
      (cond* . REST))

No need to look inside or understand `pcase.el` at all!



        Stefan