Programming in Objective-C, Sixth Edition

The Comma Operator

At the bottom of the precedence totem pole, so to speak, is the comma operator. In Chapter 5, we pointed out that inside a for statement, you can include more than one expression in any of the fields by separating each expression with a comma. For example, the for statement that begins

for ( i = 0, j = 100; i != 10; ++i, j -= 10 )  ...

initializes the value of i to 0 and j to 100 before the loop begins, and it increments the value of i and subtracts 10 from the value of j after the body of the loop is executed.

Because all operators in Objective-C produce a value, the value of the comma operator is that of the rightmost expression.