Simon Peyton-Jones wrote:
| Actually, I think it's a much bigger wart that pattern matching in let
| and where is lazy, and everywhere else is strict, than that we have an
| operator ~ on patterns with a clean compositional semantics. Way back
in
But ! patterns would restore what you want
let !(x,y) = e in ...
Arguably, it's non-uniform, but at least the strict version would be
much more convenient than switching to case.
Simon
Of course, it's nice to be able to get strict matching in a let if you
want it. But what I think is
a wart is that //patterns mean different things// in a let or where, and
in a case or lambda. That's
something you have to learn at some point, and I'd rather it was just a
question of learning what
~ means. (You have to learn what lazy pattern matching means anyway, so
you have to learn
the //semantics// of ~ -- learning the syntax too isn't hard).
BTW if let and where were strict-by-default, just as lambda and case
are, then there would be
no need for ! patterns, would there?
John
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