This whole area is clearly somewhat troublesome:
> On Sep 10, 2020, at 12:05 PM, Iavor Diatchki <iavor.diatc...@gmail.com> wrote:
>
> 3. nested bang patterns in pattern bindings should count as "uses" of the
> value and therefore should be strict. For example if I write `let ( !x, !y )
> = undefined in ()`, I think this should be equivalent to `let (x,y) =
> undefined in x `seq` y `seq` ()`. With the current behavior the bang
> patterns don't do anything, while my guess would be that most people would
> expect the suggested behavior instead. As usual, we should not allow that at
> the top level.
This isn't quite right.
Consider
> ex0 = let ( !x, !y ) = undefined in ()
> ex1 = let ( !x, !y ) = (5, undefined) in x
> ex2 = let ( !x, y ) = (5, undefined) in x
ex0 converges, because let-bindings are lazy by default.
ex1 diverges, because the bang on y means that, when the patten-match happens
at all, x and y are bound strictly. So bangs *do* matter in nested patterns
within pattern bindings. By contrast, ex2 converges.
Again, I'm not arguing in favor of the current behavior, but I want to make
sure we're all as informed as possible in this debate.
Richard
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