On Tue, Mar 19, 2013 at 3:58 PM, Christopher Done
From the paper Fun with Type Funs, it's said:
One compelling use of such type functions is to make type coercions implicit, especially in arithmetic. Suppose we want to be able to write add a b to add two numeric values a and b even if one is an Integer and the other is a Double (without writing fromIntegral explicitly).
And then an Add class is defined which can dispatch at the type-level to appropriate functions which resolve two types into one, with a catch-all case for Num.
Has anyone put this into a package, for all common arithmetic operations? I would use it. Doing arithmetic stuff in Haskell always feels labored because of having constantly convert between number types.
I prefer the current way (which is interestingly what Go chose as well). With implicit casts it's easy to shoot yourself in the foot e.g. when doing bit-twiddling. These two are different f :: Word8 -> Int -> Word32 f w8 n = fromIntegral (w8 `shiftL` n) f' :: Word8 -> Int -> Word32 f' w8 n = (fromIntegral w8) `shiftL` n