I was looking at GHC.Unicode library source and realized that almost all the Haskell internal libraries avoid tacit programming (aka point-free style) most of the time. Simple functions can be easily converted, such as:
isLatin1 :: Char -> Bool
isLatin1 c = c <= '\xff'
Resulting in:
isLatin1 :: Char -> Bool
isLatin1 = (<= '\xff')
But there are cases where I can't apply it, such as when I have more complex functions, like:
isOctDigit c = c >= '0' && c <= '7'
Is hard to deduct a way to compose the operations. I don't mean to get in the range, I mean to do multiple operations just by composing functions. The following:
isOctDigit = (>= '0') && (<= '7')
Is not valid, and also (>= '0') . (<= '7') clearly cannot happen because of the different return types.
Taking account these observations, I have the following questions:
- When should I use point-free programming instead of explicit it all?
- Why GHC prefer to explicit instead of use partial functions?
- How can I compose two functions of different types without being explicit, such as in the example?