Re: Instead of pcase

[Dmitry Gutov]

On 30/11/2023 05:37, Richard Stallman wrote:
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>
>    > I guess that's the point I wanted to underscore: that those pcase uses
>    > are more-or-less optimal in terms of complexity (for its ultimate
>    > goals), that in most cases it comes from the problem domain rather than
>    > from the solution.
>
> I think the way you measure "complexity" is different from the way I
> measure it.  I suspect that your measure does not count the complexity
> of learning `pcase' -- that it assumes the reader knows that already.
>
> That complexitu is what I am trying to eliminate.
>
> I also think that you measure "complexity" as the opposite of terseness,
> so that a couple of uses of `match-set' is in your view "added complexity".
> However, terseness is what makes `pcase' more complex.

You haven't posted your conversion, but I suspect it was not just less 
terse, but it also forced the programmer to repeat the same sets of 
information: first, in the predicate, to check that the value has a 
certain structure, and then in the matcher, to deconstruct the structure 
and create a set of variable bindings.

This repetition both adds verbosity and increases the chance to make a 
mistake in one of the two places. But once you eliminate it, I believe 
the result has to look like a more verbose pcase. Choosing an new syntax 
should be possible (indeed, somebody posted a link to a similar 
construct in Racket which is more wordy), but then those who don't like 
high-level constructs probably won't like it either.