Is

The reserved word is appears as:

• an operator symbol in object-oriented programming, or as a
• a modifier qualifying routine variable (is nested).

Operator

The operator is tests, whether an object (first operand) is an instance of a class or its children.

fruit is citrusFruit

is equivalent to

fruit.inheritsFrom(citrusFruit)

. The expression is true if and only if fruit descends from citrusFruit.

Modifier

If {$modeSwitch nestedProcVars+} or {$mode ISO} routine variables declared with the modifier is nested allows those to be assigned to nested routines. Otherwise only global routines' addresses can be assigned to routine variables.

From the Free Pascal wiki, page "Is", as it stood on 2020-05-16 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.