HP 3000 Manuals HP 3000 Manuals
Comma Operator
The comma operator is a binary operator whose operands are expressions.
The expression operands are evaluated from left to right.
Syntax
expression ::=
assignment-expression
expression , assignment-expression
Description
The comma operator is a "no-operation" operator. Its left operand is
evaluated for its side effects only. Its value is discarded. The right
operand is then evaluated and the result of the expression is the value
of the right operand.
Because the comma is a punctuator in lists of function arguments, you
need to use care within argument lists to ensure that the comma is
treated as a comma operator and not as an argument separator.
f(a, (b=7, b), c);
This example passes three arguments to f(). The first is the value of a,
the second is the value of b which is set equal to 7 before the function
call, and the third is the value of c. The comma separating the
assignment expression and the argument b is enclosed in parentheses. It
is therefore interpreted as a comma operator and not as an argument
separator.
Examples
func(a, (b=0, b), c) /* set b to 0 before passing it to func. */
index++, a = index /* increment index and then assign it to a.*/
i=0, j=0, k=0 /* initialize i,j,k to 0 */