This can be better understood by taking some examples:
First:
Consider an expression:
x = ++j;
But for time being, if we need to assign a temporarily debug value, then we can write.
x = DEBUG_VALUE, ++j;
Second:
Comma ,
operators are frequently used in for()
-loop e.g.:
for(i = 0, j = 10; i < N; j--, i++)
// ^ ^ here we can't use ;
Third:
One more example(actually one may find doing this interesting):
if (x = 16 / 4), if remainder is zero then print x = x - 1;
if (x = 16 / 5), if remainder is zero then print x = x + 1;
It can also be done in a single step;
if(x = n / d, n % d) // == x = n / d; if(n % d)
printf("Remainder not zero, x + 1 = %d", (x + 1));
else
printf("Remainder is zero, x - 1 = %d", (x - 1));
PS: It may also be interesting to know that sometimes it is disastrous to use ,
operator. For example in the question Strtok usage, code not working, by mistake, OP forgot to write name of the function and instead of writing tokens = strtok(NULL, ",'");
, he wrote tokens = (NULL, ",'");
and he was not getting compilation error --but its a valid expression that tokens = ",'";
caused an infinite loop in his program.