Re: New draft (#5) and last call for comments on SRFI 257: Simple extendable pattern matcher with backtracking
Wolfgang Corcoran-Mathe 20 Oct 2025 16:39 UTC
On 2025-10-20 15:52 +0000, Sergei Egorov wrote:
> - Consistency. If the constructor (list x y z) makes no promise
> about the evaluation order of `x`, `y`, and `z`, the pattern
> (~list x y z) should not impose a matching order either.
This is a good argument, but the presence of binding expressions
makes the situation more complicated. Unspecified evaluation order
is good; unspecified scope is not. No weakness is more deadly for
matching macros.
I second (third?) Daphne & Marc here. If the matching order is
unspecified, then ban variable references that depend on order.
Otherwise, impose clear semantics for scope.
--
Wolfgang Corcoran-Mathe <xxxxxx@sigwinch.xyz>