I'm brand new to haskell and I'm having trouble using classes. The basic idea
is I want two classes, Sine and MetaSine, that are both instances of ISine.
This way I can use the act method and recurse through the metasines and sines.
Here's my code:
module Main
where
class ISine a where
period :: a -> Integer
offset :: a -> Integer
threshold :: a -> Integer
act :: (ISine b) => Integer -> a -> b
on :: Integer -> a -> Bool
--on needs offset, period, threshold
on time self = (mod (time-(offset self)) (period self)) < (threshold self)
data Sine =
Sine {
period :: Integer,
offset :: Integer,
threshold :: Integer,
letter :: String
}
instance Sine ISine where
act time (Sine self)
|on time self = [letter self]
|otherwise = []
data MetaSine =
MetaSine {
period :: Integer,
offset :: Integer,
threshold :: Integer,
sines :: (ISine a) => [a]
}
instance MetaSine ISine where
act time (MetaSine self)
|on time self = foldr (++) (map (act time) (sines self))
|otherwise = []
The errors I get involve multiple declarations of period, offset, and
threshold.
Any help would be greatly appreciated.
-Thomas
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