Boolean Keywords - AMX AXCESS CONTROL SYSTEM PROGRAM Instruction Manual

FIG. 21 An example of how a Boolean expression table is used to compare multiple conditions.
The Boolean expression tables in FIG. 22 are a quick reference guide for the result of a Boolean
expression.
FIG. 22 Sample Boolean truth table results

Boolean Keywords

The Boolean keywords supported by Axcess are described below:
Boolean Keywords
SELECT...ACTIVE
ELSE
IF
The IF statement provides
conditional branching of pro-
gram flow.
Axcess Programming Language
The SELECT...ACTIVE statement allows easy placement of several branches
from one path.
Syntax:
SELECT
{
ACTIVE (expression 1) : (* Statement 1 *)
ACTIVE (expression 2) : (* Statement 2 *)
ACTIVE (expression 3) : (* Statement 3 *)
(* ...etc. *)
}
Each one of the expressions is evaluated in order, until one is found to be true.
The statements associated with that true expression are then executed, and
the path then flows to whatever statements follow the closing brace. Using a
SELECT...ACTIVE is much preferred to multiple IF...ELSE IF statements, as it
uses less memory and runs faster.
If the corresponding IF statement is false, the program will jump to this section
of the IF...ELSE set of statements.
See IF for details.
Every IF statement must be followed by an expression enclosed in parenthe-
ses. This provides the beginning of a conditional execution of statements. For
example:
IF (expression)
(* Statement 1 *)
If the expression is true, Axcess executes Statement 1 and then continues with
whatever statements follow. If the expression is false, Statement 1 is ignored. If
Statement 1 is a compound statement, it must be enclosed in braces.
IF and the Boolean Expressions
67