In scope-passing style: use a Movable b instead of Ur b
#473
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I think I've got all the places where I could do this. @Qqwy did you have other places is mind that I might have missed? |
Functions of the form ```haskell f :: (A %1 -> Ur b) %1 -> Ur b ``` are now of the form ```haskell f :: Movable b => (A %1 -> b) %1 -> b ``` The new type is strictly more general. Technically this seems to involve some extra allocations here and there. I expect it to be negligible (we don't want to call too many scoped functions anyway). The extra allocation is interesting, in that it's not always strictly necessary: when returning an `Int`, I don't need to produce an `Ur Int` to make sure that I've actually forced everything, just returning the forced `Int` would do the trick. Yet we use an `Ur Int` to communicate that we've indeed done the job (in some cases the optimiser can actually remove the extra allocation, but not in every case as far as I can tell). Maybe there are cheaper way to tell the compiler that we've, in fact, moved the value. But that's a question for the future. See #468 for the initial discussion.
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@aspiwack Thanks for tagging me! I think you've caught them all. 🚀 |
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Let me merge then. |
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Functions of the form
are now of the form
The new type is strictly more general. Technically this seems to involve some extra allocations here and there. I expect it to be negligible (we don't want to call too many scoped functions anyway).
The extra allocation is interesting, in that it's not always strictly necessary: when returning an
Int, I don't need to produce anUr Intto make sure that I've actually forced everything, just returning the forcedIntwould do the trick. Yet we use anUr Intto communicate that we've indeed done the job (in some cases the optimiser can actually remove the extra allocation, but not in every case as far as I can tell). Maybe there are cheaper way to tell the compiler that we've, in fact, moved the value. But that's a question for the future.See #468 for the initial discussion.