Increment-decrement in c

Question

If

void main()
{ 
  int i=2,j=4; 
  i=+++i+j; //is not an error 
  i=---i+j; // is a L-value required error..
}

could anyone please explain in detail the concept behind multiple increments and decrements..

What are you intending to do with these multiple increments and decrements? — ccozad, Jan 21 '14 at 18:11
sorry about writing unreadable code...but could you explain me in the context of this question.. — john fedric, Jan 21 '14 at 18:20
@user2132128 - If you writing unreadable code then it is difficult to maintain/understand. If you write code that is readable then you do not run into this problem in the first place. So to answer your question - do not write unreadable code — Ed Heal, Jan 21 '14 at 18:22
Actually i don't use stackoverflow regularly..sorry for that.. — john fedric, Jan 21 '14 at 18:25
@user2132128 - It is nowt to do with SO. Just write readable code — Ed Heal, Jan 21 '14 at 18:26
i have already apologized twice on the same..could you please leave that.. — john fedric, Jan 21 '14 at 18:28
I don't see any multiple increments or decrements, you're just mixing the +/- operator with the ++/-- operator, and '+1' is getting treated different that '-1'. — woolstar, Jan 21 '14 at 18:39

score 0 · Answer 1 · answered Jan 21 '14 at 18:35

0

I think the parser is not able to parse it in the format it wants it to be. Try using parenthesis as below. It would work.

i=-(--i)+j;

answered Jan 21 '14 at 18:35

Saurabh

The question is what's different about the `-` operator and the `+` operator that the first one works. – woolstar Jan 21 '14 at 18:39
exactly sir..could you please explain me why first one works.. – john fedric Jan 21 '14 at 18:43
In both cases the program exhibits undefined behaviour and the output could be anything. 1. main should return int not void. In C returning void is an extension that not all compilers support making the code non-portable, in C++ it is just undefined behaviour. 2. both cases break the part of the standard that specifies variable may not be accessed more than once between sequence points where at least one of those accesses is to alter the variables value. The standard states that in such a case the behaviour will be undefined. I suggest you look sequence points and undefined behaviour on web. – Saurabh Jan 21 '14 at 20:35

1 Answers1