[Haskell-beginners] Writing a polymorphic function in Haskell
Matt Williams
matt.williams45.mw at gmail.com
Fri Sep 22 19:53:55 UTC 2017
Dear All,
I am having problems writing a polymorphic function.
I have a type that has two constructors:
data Arg = IndArg {evi::Evi, t1::Treatment, t2::Treatment, out::Outcome,
dir::Direction}
| MetaArg {target::EviType}
deriving (Show)
I have a function checks for conflict:
checkConflict :: Arg -> Arg -> Bool
checkConflict a b = if t1 a == t1 b && t2 a == t2 b && dir a /= dir b then
True
else False
However, I can't make this work with both types of Argument - if I pass it
MetaArg, it raises an error.
In another language, I would write something like:
checkConflict(ArgA,ArgB):
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