The infix style of writing an expression is just a convenience; we can also write an expression in prefix form, where the operator precedes its arguments. To do this, we must enclose the operator in parentheses.
举例如下：
ghci> 3 ^ 4
81
ghci> (^) 3 4
81
ghci> ^ 3 4
<interactive>:68:1: parse error on input ‘^’