[Haskell-cafe] Checking a value against a passed-in constructor?
danielkcook at gmail.com
Mon Jun 1 23:39:44 EDT 2009
(Relatively new to Haskell here ..)
So I have the following:
data MyVal = Atom String
| Bool Bool
And I want to do something like this
check :: (Bool -> MyVal) -> MyVal -> True
check f (f x) = True
check _ _ = False
What that means is I want to pass a MyVal constructor and a MyVal, and
return True if the second argument was constructed with the first.
More generally, I'd like to be able to do
genCheck :: (* -> MyVal) -> MyVal -> True
genCheck f (f x) = True
genCheck _ _ = False
So that I can pass in _any_ MyVal constructor and let the function
just check if the second argument was constructed with the first,
without caring which constructor it is.
What is the preferred way to do this, since neither of those functions
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