Sambar Server CScript Flow Control

Sambar Server Documentation

CScript Flow Control

Programs typically contain some construct that loops within the program, performing repetitive actions on a stream of data or a region of memory. There are several ways to loop in CScript. Two of the most common are the while loop:


while (expression)
{
    ...block of statements to execute...
}

and the for loop:


for (expression_1; expression_2; expression_3)
{
    ...block of statements to execute...
}

The while loop continues to loop until the conditional expression becomes false. The condition is tested upon entering the loop. Any logical construction (see below) can be used in this context. The for loop is a special case, and is equivalent to the following while loop:


expression_1;

while (expression_2)
{
    ...block of statements...

    expression_3;
}

Conditional Expressions

Conditional expressions are used within the if and while constructs:


if (conditional_1) 
{
    ...block of statements executed if conditional_1 is true...
}
else if (conditional_2)
{
    ...block of statements executed if conditional_2 is true...
}
else
{
    ...block of statements executed otherwise...
}

Conditionals are logical operations involving comparison of quantities (of the same type) using the following operators:

Conditional Operators Description

< smaller than

<= smaller than or equal to

== equal to

!= not equal to

>= greater than or equal to

> greater than

Boolean Operators Description

&& and

|| or

! not

Conditional Operators	Description
<	smaller than
<=	smaller than or equal to
==	equal to
!=	not equal to
>=	greater than or equal to
>	greater than
Boolean Operators	Description
&&	and
\|\|	or
!	not

Conditional operators are typically used to combine logical expressions, for example:


	x < 20 && x >= 10

These logical connectives employ a technique known as lazy evaluation. The left hand operand is evaluated first, and then the right hand is evaluated only one if it is required. Clearly false && anything is always false, true || anything is always true. In such cases the second test is not evaluated. The not operand reverses the state of a single logical value.


if ( ! acceptable )
        printf("Not Acceptable !!\n");

Another conditional use is in the switch construct:


switch (expression)
{
case const_expression_1:
    {
        ...block of statements...
    }
    break;

case const_expression_2:
    {
        ...block of statements...
    }
    break;
default:
    {
        ...block of statements..
    }
}

The appropriate block of statements is executed according to the value of the expression, compared with the constant expressions in the case statement. The break statements insure that the statements in the cases following the chosen one will not be executed.