IF

IF statements are used for conditional execution of code in VPL programs.

IF <expr> THEN
 statement;
ELSIF <expr> THEN
 statement;
ELSE
 statement;
END_IF;

<expr> is an expression that evaluates to a BOOL, and it is therefore always either TRUE or FALSE. Based on the <expr>, the code after the THEN keyword is either executed or bypassed.

Example:

INCLUDE rtcu.inc
 
VAR
  a   : INT;
  b   : INT;
  str : STRING;
END_VAR;
 
PROGRAM test;
 
BEGIN
 
  IF a > b THEN
     str := "a is grater than b";
  ELSIF a = b THEN
     str := "a equals b";
  ELSE
     str := "a is lesser than b";
  END_IF;
 
END;
 
END_PROGRAM;