Re: [Haskell-cafe] wildcards for type variables?

On Wed, Jan 13, 2010 at 4:59 AM, Brandon S. Allbery KF8NH wrote:

On Jan 13, 2010, at 05:54 , David Virebayre wrote:

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On Wed, Jan 13, 2010 at 12:29 AM, Evan Laforge wrote:

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Occasionally I have a function with an unused argument, whose type I don't want to restrict.  Thus:

f :: _unused -> A -> B f _ a = b

I probably misunderstood the problem, why not f:: a -> A -> B

He's looking for the self-documentation aspect of "this argument is completely irrelevant".  Neither rolling a random unused type variable nor "forall"ing it (my first idea) really accomplishes that.

Isn't that what we have here? a function of type (a -> A -> B) cannot use the first argument in any meaningful way. But once you start throwing in higher ranked types you might have to think a bit to come to that conclusion. Antoine