PML Expressions

PML Customisation User Guide

PML Expressions

An expression consists of operators and operands.

2 + 3 

is an expression, where 2 and 3 are the operands, and + is the operator. The result of this expression is 5.

Expressions can (and normally do) contain variables and, in AVEVA E3D™, expressions will often contain names of AVEVA E3D™ element types, attributes and pseudo-attributes.

Expressions can also contain arithmetic and trigonometric functions, such as the SIN trigonometric function.

Often, expressions will contain logical operators:

!height GT !width

Here the logical operator GT is being be used to test if !height is greater than !width.

Each expression has a type such as REAL, STRING or BOOLEAN. All the elements in an expression must be of the correct type. For example:


!X + 'text'	$* wrong, Wrong, WRONG!

is meaningless if !X is REAL and will result in an error. (But see Concatenation for using the concatenation operator to convert different types to STRING.)