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Version: 5.x

ISCLASS operator

The ISCLASS operator creates a property that implements a signature matching operator.

Syntax​

ISCLASS(expr)
info

There is an alternative syntax for this operator, which has been deprecated since version 5. It will be removed in future versions:

CLASS(expr)

Description​

The ISCLASS operator creates a property that determines, from a class perspective, whether the expression specified in the operator can have a non-NULL value for the given arguments.

Parameters​

  • expr

    Expression that describes and creates a property, for which a set of parameter classes - a signature - is inferred. Matching this signature will be checked.

Example​

CLASS Person;
name = ABSTRACT CASE STRING[100] (Person);

CLASS Student : Person;
studentName = DATA STRING[100] (Student);

name(s) += WHEN ISCLASS(studentName(s)) THEN studentName(s); // is equivalent to WHEN s IS Student THEN studentName(s)