Can anybody explain for me:
int a, b, c, d;
a = 2;
b = 4;
c = a, b;
d = (a, b);
Why c == 2 and d == 4 ???
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StoryTeller - Unslander Monica
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Trần Hồng Phát
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1Don't post code and results in images, it's a PITA to see on mobile devices, and to try your code in a compiler as well. -1 until you fix it. – Matteo Italia Dec 28 '16 at 07:26
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OK, So sorry about that. – Trần Hồng Phát Dec 28 '16 at 07:30
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1Downvote retracted. – Bathsheba Dec 28 '16 at 07:31
1 Answers
6
The two statements are both evaluated as
c = a;
d = b;
due to how the comma operator (which has the lowest precedence of any operator) works in C and C++.
For the first one, c = a is evaluated first (as = has higher precedence than the comma operator) then b (which is a no-op) is evaluated. The entire expression has a value b but that's not assigned to anything.
For d = (a, b);, (a, b) is first evaluated due to the parentheses. This has a value b, and that is assigned to d.
Bathsheba
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1@TrầnHồngPhát - You should accept this answer, since it helped you and it's spot on. – StoryTeller - Unslander Monica Dec 28 '16 at 07:33