c++ - comma operator in if condition - 


int = 1, b = 0;  if(a, b)    printf("success\n"); else    printf("fail\n");  if(b, a)    printf("success\n"); else    printf("fail");

this cpp file , got output in visual studio 2010 

fail success

why behavior? please explain?

http://en.wikipedia.org/wiki/comma_operator:

in c , c++ programming languages, comma operator (represented token ,) binary operator evaluates first operand , discards result, , evaluates second operand , returns value (and type).

in first if:

if (a, b)

a evaluated first , discarded, b evaluated second , returned 0. condition false.

in second if:

if (b, a)

b evaluated first , discarded, a evaluated second , returned 1. condition true.

if there more 2 operands, last expression returned.

if want both conditions true, should use && operator:

if (a && b)

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