RE: Bang patterns, ~ patterns, and lazy let

I've updated the Wiki to add your strict proposal, but rather briefly. If you want to add stuff, send it to me and I'll add it. Meanwhile: | And as a consequence, it is no longer possible to transform a pair of | bindings into a binding of a pair. In Haskell 98, | | p1 = e1 | p2 = e2 | | is always equivalent to | | (~p1, ~p2) = (e1,e2) In your strict proposal, I'm sure you hope that the above pair would be equivalent to (p1,p2) = (e1,e2) which would be even nicer. But sadly I don't think it is, because that'd change the strongly connected component structure. Somehow that smells wrong. Simon

Simon Peyton-Jones wrote:
I've updated the Wiki to add your strict proposal, but rather briefly. If you want to add stuff, send it to me and I'll add it.
Meanwhile:
| And as a consequence, it is no longer possible to transform a pair of | bindings into a binding of a pair. In Haskell 98, | | p1 = e1 | p2 = e2 | | is always equivalent to | | (~p1, ~p2) = (e1,e2)
In your strict proposal, I'm sure you hope that the above pair would be equivalent to (p1,p2) = (e1,e2) which would be even nicer.
But sadly I don't think it is, because that'd change the strongly connected component structure. Somehow that smells wrong.
Simon
What have you got in mind? ANY tupling of bindings may change the SCC structure, and hence the results of type inference--I'm taking that as read. But that still leaves the question of whether the dynamic semantics of the program is changed. Let's assume for the time being that all bindings carry a type signature--then the SCC structure is irrelevant, isn't it? Or am I missing something here? I'm under the impression that the *dynamic* semantics of p1 = e1 p2 = e2 *would* be the same as (p1,p2) = (e1,e2) under my strict matching proposal. I don't see how the SCC structure can affect that. John
participants (2)
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John Hughes
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Simon Peyton-Jones