HP C/iX Reference Manual (31506-90011)

92 Chapter6
Statements
The for Statement
The for Statement
The for statement evaluates three expressions and executes the loop body until the second
expression evaluates to false.
Syntax
for ( [expression1] ; [expression2] ; [expression3] ) statement
Description
The for statement is a general-purpose looping construct that allows you to specify the
initialization, termination, and increment of the loop. The for uses three expressions.
Semicolons separate the expressions. Each expression is optional, but you must include
the semicolons.
Expression1 is the initialization expression that typically specifies the initial values of
variables. It is evaluated only once before the first iteration of the loop.
Expression2 is the controlling expression that determines whether or not to terminate the
loop. It is evaluated before each iteration of the loop. If
expression2 evaluates to a
nonzero value, the loop body is executed. If it evaluates to 0, execution of the loop body is
terminated and control passes to the first statement after the loop body. This means that if
the initial value of
expression2 evaluates to zero, the loop body is never executed.
Expression3 is the increment expression that typically increments the variables
initialized in
expression1 . It is evaluated after each iteration of the loop body and before
the next evaluation of the controlling expression.
The for loop continues to execute until
expression2 evaluates to 0, or until a jump
statement, such as a break or goto, interrupts loop execution.
If the loop body executes a continue statement, control passes to
expression3 . Except for
the special processing of the continue statement, the for statement is equivalent to the
following:
expression1;
while ( expression2 ){
statement
expression3;
}
You may omit any of the three expressions. If expression2 (the controlling expression) is
omitted, it is taken to be a nonzero constant.
For example:
for (i=0; i<3; i++) {
func(i);
}
This example calls the function func three times, with argument values of 0, 1, and 2.