G'day all.
Quoting John Meacham
I can't speak for why they weren't included in Haskell 98, but on occasion I have wanted something like
f :: Int -> !Int -> Int f x y = foo
which would translate to:
f :: Int -> Int -> Int f _ y | seq y False = undefined f x y = foo
although I am not sure how useful it would actually be.
Although that's not quite what you want. Having ! part of the type signature suggests that it's the caller's job to do the seq, not the callee's. This way, you can avoid the eval if the caller has already evaluated the argument, or if the caller knows that evaluation is a no-op.
another thing which might be handy is ' !' completely analogous to $!, with the exact same precedence as normal functional application (think space-bang, just like dollar-bang)
Yes, I don't like the precedence (or associativity, for that matter) of $! either. Cheers, Andrew Bromage