Examples
In this example, the differing behavior between the second and third lines is due to the comma operator having lower precedence than assignment.
// Examples: Descriptions: Values after line is evaluated: int a=1, b=2, c=3, i=0; // comma acts as separator in this line, not as an operator ... a=1, b=2, c=3, i=0 i = (a, b); // stores b into i ... a=1, b=2, c=3, i=2 i = a, b; // stores a into i. Equivalent to (i = a), b; ... a=1, b=2, c=3, i=1 i = (a += 2, a + b); // increases a by 2, then stores a+b = 3+2 into i ... a=3, b=2, c=3, i=5 i = a += 2, a + b; // increases a by 2, then stores a into i. Equivalent to (i = (a += 2)), a + b; ... a=5, b=2, c=3, i=5 i = a, b, c; // stores a into i ... a=5, b=2, c=3, i=5 i = (a, b, c); // stores c into i ... a=5, b=2, c=3, i=3Note that comma cannot be used in indexing multidimensional array: the code A evaluates to A with the i discarded, instead of the correct A. This differs from the syntax in Pascal, where A is correct, and can be a source of errors.
Read more about this topic: Comma Operator
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