Question about operator precedence in C++

Question

The output is 34, but how is this expression evaluated?

How would it be with parentheses?

The correct operator precedence is:

a += ((((((2 * i++) % 5) * 4) + (--j)) - (3 / k)) + 2);

But I think correct should be:

a += (((((2 * i++) % (5 * 4)) + (--j)) - (3 / k)) + 2);

#include <iostream>
using namespace std;

int main()
{
    int a = 3, i = 12, j = 14, k = 16;
    a += 2 * i++ % 5 * 4 + --j - 3 / k + 2;
    cout << a;
}

You may check docs if you have any doubts. It describes both precedence and associativity. — user2956272, Commented Nov 9, 2019 at 23:22
What do you think it should be and how do you come to that conclusion? — 1201ProgramAlarm, Commented Nov 9, 2019 at 23:35
Usually I'm one of the first downvoters but in this question I don't understand the downvotes. Could someone explain it to me? — Thomas Sablik, Commented Nov 9, 2019 at 23:52

Thomas Sablik · Accepted Answer · 2019-11-09 23:50:13Z

3

The operators *, / and % have same precedence and are grouped left to right. Therefore it is ((2 * i++) % 5) * 4 and not (2 * i++) % (5 * 4)

edited Nov 9, 2019 at 23:50

answered Nov 9, 2019 at 23:43

Thomas Sablik

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1

in the language of the standard, those operators are grouped left to right. “Evaluated” is easily misread here to suggest order of evaluation of their arguments, which is an entirely different matter. +1.
– Pete Becker
Commented Nov 9, 2019 at 23:47
1

@PeteBecker Changed it.
– Thomas Sablik
Commented Nov 9, 2019 at 23:50

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