Describes the rules for the '=' and '!=' signs.

Equal to (=) or Not Equal to (!=)

Overview

Use the symbol

to notate the inequality 'equal to', or

!=

to notate the inequality 'not equal to'. In fact 'equal to' is an equality, but for consistency reasons the equal sign is listed below the inequality symbols.

For example:

A = B AND B != C

means:

A is equal to B and B is not equal to C

The equal and not-equal signs can also be used to test if a variable has been set, by testing on the value ??????.

Details

The expressions a and b in the inequality a = b, or a != b should be substituted by any of the following:
- a fixed text string, for example hypertension
- a fixed numerical value, for example 12.3, also valid is 12,3
- a global variable, for example $hour$
- any other variable or variable parameter, for example $Design.Constant 1.Value$, or $LastName$.

Variables are substituted by their current values at the time the inequality is processed. Spaces around the expressions are trimmed automatically.

The way the inequality is solved depends on the type of its expressions:

Both expressions are numbers
The inequality is handled according to numerical rules.

Both expressions are textual
If a text string is to be compared to another text string, then comparison is case sensitive.
For example:
Hello = hello evaluates to FALSE, because the texts are not exactly equal.
$var$ = ?????? evaluates to TRUE in case the variable $var$ has not been set.
$var$ != ?????? evaluates to TRUE in case the variable $var$ has been set to any value.
$var$ = evaluates to TRUE in case the variable $var$ has been set to an empty value, but it is better to check this like this:
"$var$" = ""
or:
"$var$" = " " to check if $var$ has been set to a space-character

One of both expressions is textual, the other is a number
If one of both expressions is a text, then the other expression is also handled like text.