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c++operator-precedence

Subscript operator precedence

The subscript operator has the second highest operator precedence (see the table). However, it seems to behave as if it had a low precedence. For example:

int arr[] = {10,20,30,40,50};
cout << arr[1+2];

This code outputs 40, which suggests that the result of + was available before the application of the subscript operator, which in turn suggests that + has a higher precedence than the subscript operator. What am I missing and how does the high precedence of the subscript operator express itself?

Solution

  • The subscript operator [] is applying to arr and the argument is 1 + 2. The argument is not relevant to the precedence of the [] operator.

    Cf. an expression like 1 + arr[1 + 2]. That is grouped as 1 + (arr[1 + 2]) due to the precedence that you cite, not (1 + arr)[1 + 2] which would be some curious pointer arithmetic!