> I admit I don't feel as strongly any more. My argument in that thread was > from the standpoint of a language designer: there is really no reason, a > priori, for an unboxed-tuple binding to be strict. What controls strictness > is whether the bound variables are of unlifted type. However, I'm currently > in more sympathy with language users, who (for whatever reason) seem to > think that bindings with #s in them should be strict. (I have this > intuition myself, even though it's not quite warranted on technical > grounds.) >
A middle ground could be to not allow unbanged patterns for unboxed tuples. Since they currently exist, we could also simply emit a warning, saying: “this is probably not what you want, do add an exclamation mark”. > What do we think of > > pattern Unl x y = (# x, y #) > > ex1, ex2 :: () > ex1 = let Unl x y = Unl undefined undefined in () > ex2 = let Unl x y = undefined in () > > > ? Today, both ex1 and ex2 evaluate to (). If we were to change the > specification here, would we consider any unlifted-type pattern (where the > type of the pattern itself is unlifted, independent of the type of any of > its bound variables) to be banged? Or would it be a super-special case for > unboxed tuples? > Ooh… pattern synonyms for unboxed tuple. I must confess that I don't know what the semantics of these ought to be. It does look like an interesting can of worms. How do they currently desugar?
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