+-*/
-associativity : L to R
-precedence : */ have higher Precedence than +-

Infix: 1+2+3     | g -3 * 2 + 1  | 4 * (1 + 2) | 4 * 1 + 2
PrefixL ++ 1 2 3 | + - g * 3 2 1 | * 4 + 1 2   | + * 4 1 2

(a[f(x)] = a[f(x)] + 3;
(i = f(x);
(a[i] = a[i] + 3;