[Haskell-cafe] Custom unary operator extension?

I find it unfortunate that one can't (I guess) define custom unary operators in Haskell. Is this correct? If so, is this just because eg (* 100) declares a function that partially applies the * operator, so this syntax disallows unary operators? Could this be fixed by introducing a different syntax for partial operator application? E.g. (? * 100) instead of just (*100)? This would also fix the ambiguity between (-10) as being either the number minus 10 or the "subtract by 10' function. Cheers, Peter