A question about Haskell 98: is this legal:
data T = T1 Int Int Int
| T2 Float Float Float
f (T1 {}) = True
f (T2 {}) = False
The point is that T is not declared using
record syntax, but f nevertheless uses record
syntax in the pattern match to mean "T1 with any arguments".
This is less clumsy than writing
f (T1 _ _ _) = True
f (T2 _ _ _) = False
Some people, it turns out, use this a lot. Hugs accepts it.
GHC didn't until recently. But is it Haskell 98.
The Haskell 98 report, interpreted literally, certainly does
not prohibit it, though I certainly didn't have this example in mind.
So I propose to add a clarifying sentence somewhere to make
it clear that this *is* ok. Unless someone yells.
As ever, this will go on the "Typos" page (I have two or three
things to add there).
This is hardly a big deal, but I'm in the habit of publishing
proposals before implementing them.
Simon
