David Mertz wrote:
> I have a little bit of skepticism about the pattern matching syntax, for
> similar reasons to those Larry expresses, and that Steve Dower mentioned on
> Discourse.
> Basically, I agree matching/destructuring is a powerful idea. But I also
> wonder how much genuinely better it is than a library that does not require
> a language change. For example, I could create a library to allow this:
> m = Matcher(arbitrary_expression)
> if m.case("StringNode(s)"):
> process_string(m.val)
> elif m.case("[a, 5, 6, b]"):
> process_two_free_vars(*m.values)
> elif m.case("PairNone(a, b)"):
> a, b = m.values
> process_pair(a, b)
> elif m.case("DictNode"):
> foo = {key, process_node(child_node) for key, child_node in
> m.values.items()}
> I don't disagree that the pattern mini-language looks nice as syntax. But
> there's nothing about that mini-language that couldn't be put in a library
> (with the caveat that patterns would need to be quoted in some way).
What you are proposing here is very similar in effect to executing pattern
matching statements using `eval`. What is the advantage of implementing the
pattern matching functionality in a library if the user interface for that
functionality has the same pitfalls as `eval`?
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