I am newbie to coding and am confused about increment and decrement operators.
int a = 10;
int b = ++a + ++a + ++a;
According to youtube videos it should print 39 but it prints 37. Can someone explain me the reason ?
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5Those youtube videos aren't very good, then. – melpomene May 08 '17 at 20:59
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1This should not be closed... – Krupip May 08 '17 at 21:00
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I feel an urge to find these videos and tell the author everything I think of him... – Eugene Sh. May 08 '17 at 21:00
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@snb Why is that? – Eugene Sh. May 08 '17 at 21:01
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1I looked at that post but cant find anything useful :( – R. Bayram May 08 '17 at 21:05
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Even the fourth answer? – Eugene Sh. May 08 '17 at 21:06
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I understood that but if i make 4 ++a it gives 51 so in that case compiler makes numbers 12 12 13 14. Why first ++a is not 11 ? I didn`t understand that. – R. Bayram May 08 '17 at 21:11
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@R.Bayram Undefined behavior is undefined. – melpomene May 08 '17 at 21:17
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1@R.Bayram: C doesn't force left-to-right evaluation (except in a few cases that don't apply here), and it doesn't require that the side effect of `++` be applied immediately after evaluation. Because of this, the result of an expression like `++a + ++a + ++a` is not guaranteed to have a consistent result across different implementations, programs, or even different runs of the same program. The behavior is *undefined*, meaning it shouldn't have *any* specific result - it's a coding error, but the compiler isn't required to complain about it. – John Bode May 08 '17 at 21:53
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What baffles me is why anyone would care about the result of such ghastly code. It only ever appears in SO questions, (thousands of them), and is of negative use to future users/visitors:( – ThingyWotsit May 08 '17 at 22:07
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@EugeneSh. https://www.youtube.com/watch?v=HvcXju_jNWQ here be the one I presume. I've left a comment, it requires upvotes to appear at top. 60k views; and we got 2 questions from it within an hour today. – Antti Haapala -- Слава Україні Sep 07 '18 at 20:40
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@melpomene ^ ;) – Antti Haapala -- Слава Україні Sep 07 '18 at 20:42