WTF, Haskell?


Prelude> (+) 1 2*3
9
Prelude> (+) 1*3 2

<interactive>:1:0:
    No instance for (Num (t -> t))
      arising from a use of `*' at <interactive>:1:0-8
    Possible fix: add an instance declaration for (Num (t -> t))
    In the expression: (+) 1 * 3 2
    In the definition of `it': it = (+) 1 * 3 2

<interactive>:1:6:
    No instance for (Num (t1 -> t -> t))
      arising from the literal `3' at <interactive>:1:6-8
    Possible fix: add an instance declaration for (Num (t1 -> t -> t))
    In the second argument of `(*)', namely `3 2'
    In the expression: (+) 1 * 3 2
    In the definition of `it': it = (+) 1 * 3 2
Prelude>

Functions have higher precedence than operators.

Your first line means this:

((+) 1 2) * 3

Your second line means this:

((+) 1) * 3 2
which is naturally invalid