Loops

PRX allows us to create different kinds of loops. With them, we can either iterate over a number range or over lists.

Usage

DO-Statement

To iterate over a number range, we can use the DO-statement.

/* create new variables */
SET &TEST_IDX = 1;
SET &TEST_IDX_MAX = 10;

/* start DO-loop */
DO(&TEST_IDX,LE,&TEST_IDX_MAX);
    CALL SAY(&TEST_IDX);
    
    SET &TEST_IDX = &TEST_IDX + 1;
DO(END);

In the above example, we've utilized a DO-loop to print the numbers 1 to 10. A DO-loop accepts three parameters:

DO(&START,CONDITION,&END);

Be careful to count up the index variable! Otherwise your program will loop indefinitely.

FOREACH-Statement

To iterate over a list, we can use the FOREACH-statement.

/* create new list */
SET &TEST_LST = [1,2,3,4,5,6,7,8,9,10];

/* start FOREACH-loop */
FOREACH(&TEST_LST AS &TEST_ITEM);
    CALL SAY(&TEST_ITEM);
FOREACH(END);

Here, we've achieved the same thing with a FOREACH-loop. A FOREACH-loop generally consists of two parameters.

FOREACH(&LIST AS &ITEM);

Flow Control

In order to manipulate the flow of a loop, we can use the BREAK- and CONTINUE-statements.

BREAK-Statement

With the BREAK-statement, we can break outside of a loop prematurely.

/* create new variable */
SET &IDX = 1;
SET &MAX = 10;

/* create loop */
DO(&IDX,LE,&MAX);
    IF(&IDX GT 5);
        BREAK;
    IF(END);
DO(END);

CONTINUE-Statement

With the CONTINUE-statement, we can skip an iteration of a loop.

/* create new variable */
SET &IDX = 1;
SET &MAX = 10;

/* create loop */
DO(&IDX,LE,&MAX);
    IF(&IDX EQ 5);
        CONTINUE;
    IF(END);
DO(END);

We can also pass a NUM-parameter to BREAK or CONTINUE to affect multiple levels. This is useful in nested loops.

BREAK(2);
[...]
CONTINUE(2);

Following that, we will learn how to modularize our program using includes.