Assuming that z :: Int, you can declare an algebraic datatype
data TwoOrThree a b = Three (a, b, Int)
| Two (a, b)
deriving(Show, Eq) -- so you can experiment
And then define expand as
expand :: TwoOrThree a b -> (a, b, Int)
expand (Three tuple) = tuple
expand (Two (a, b)) = (a, b, 1)
Tom (amindfv)
On Oct 2, 2011 6:04 AM, "Du Xi" <sdiy...@sjtu.edu.cn> wrote:
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