Rexx - Loops

So far we have seen statements which have been executed one after the other in a sequential manner. Additionally, statements are provided in Rexx to alter the flow of control in a program’s logic. They are then classified into a flow of control statements which we will study in detail.

A loop statement allows us to execute a statement or group of statements multiple times. The following illustration is the general form of a loop statement in most of the programming languages.

Let us discuss various loops supported by Rexx.

Controlled Repetition

The do loops can be catered to carry out a controlled repetition of statements.

Syntax

The general syntax of this sort of statement is as follows.

do index = start [to pmit] [by increment] [for count] 
statement #1 
statement #2 
end 

The difference in this statement is that there is an index which is used to control the number of times the loop is executed. Secondly, there are parameters which state the value which the index should start with, where it should end and what is the increment value.

Flow Diagram

Let’s check out the flow diagram of this loop −

From the above diagram you can clearly see that the loop is executed based on the index value and how the index value is incremented.

The following program is an example of the controlled repetition statement.

Example

/* Main program */ 
do i = 0 to 5 by 2 
   say "hello" 
end 

hello 
hello 
hello