in — !in (predicates)

In any expression, the in keyword tests whether a value belongs to a collection and or the !in keyword tests whether a value does not belong to a collection.

Purpose

A predicate to test whether a value belongs or does not belong to a collection.

Context

Any expression

Syntax

(1) [?var:] className (?var1 in|!in ?var2);
(2) [?var:] className (?var1 in|!in {? var1, var2, ..., varn});

Description

Use the in keyword as a binary predicate in a condition to test whether an operand is part of another operand. The !in keyword does the negation of this test.

The operand can be expressed in two ways:

In syntax (1), the operand type must be an array or implement the java.util.Collection package.
In syntax (2), the values that compose the enumeration must be homogeneous. The enumeration contains either primitive types only or objects only.

The tests are done with equals, as in Java™ collections.

Example

rule InTestEnum
{
   when {
      ?i: Integer(intValue() in {1, 2, 3});
   }
   then {
      out.println("InTestEnum rule");
   }
}
 
 
rule InTestCollection
{
   when {
      ?i: Integer(intValue() in getValues());
   }
   then {
      out.println("InTest rule");
   }
}

with:

function int[] getValues()
{
   int values = new int[2];
   values[0] = 1;
   values[1] = 2;
   return values;
}