[Haskell-cafe] Why do functions not inherit class when renamed?

[Duane Johnson]

I'm not sure I understand what is going on here, but it seems to me  
that the following assignment of "mult = (*)" causes "mult" to lose  
out on some of the polymorphic behavior of (*).  Is that right?  If  
so, why?



> Prelude Data.Function Data.List Data.Char> let sizeMult = (*) `on`  
> length
> Prelude Data.Function Data.List Data.Char> sizeMult "Duane" "Johnson"
> 35
> Prelude Data.Function Data.List Data.Char> let mult = (*)
> Prelude Data.Function Data.List Data.Char> let sizeMult2 = mult `on`  
> length
>
> <interactive>:1:26:
>     Couldn't match expected type `Integer' against inferred type `Int'
>     In the second argument of `on', namely `length'
>     In the expression: mult `on` length
>     In the definition of `sizeMult2': sizeMult2 = mult `on` length
> Prelude Data.Function Data.List Data.Char>



Thanks,
Duane Johnson
http://blog.inquirylabs.com/