Add ifThenElse and (?) to Data.Bool

It seems this’s a very old request, see https://wiki.haskell.org/If-then-else https://wiki.haskell.org/If-then-else. I’d like to see following: ifThenElse :: Bool -> a -> a -> a ifThenElse True x _ = x ifThenElse False _ y = y infixr 1 ? (?) :: Bool -> a -> a -> a (?) = ifThenElse in Date.Bool module, it will have advantages that: + It’s more composable than syntax. + Write (xxx ? yyy $ zzz) instead of (if xxx then yyy else zzz) is more consistent with (f . g $ x) style, and save key strokes. + In module with RebindableSyntax enabled, you can import ifThenElse to get default behavior. Whether or not to be exported by Prelude is another question, but Data.Bool seems a good place to start with. Cheers~ Winter