where (test)

This construct matches objects against tests.

Purpose

Matches objects against tests.

Syntax

where <test>

Description

In the definitions part of a rule, you can use one or more where clauses with the set construct to test that an object meets one or more conditions in order to be a valid value for the variable being declared. In the definitions part of the rule, the where statement does not end with a comma. Instead, each set construct should end with a semi-colon (;).

In the if part of a rule, you can use one or more where clauses in count conditions (there is more than, there is less than, and so on) to test that an object meets one or more conditions before being counted.

In a where construct, an implicit variable that refers to the current instance of the object being tested is automatically declared. In the test, you can thus refer to potential instances of the variable as this <object> (or each <object> if they are part of a collection.)

Example

The following example shows the definitions part of a rule that defines the local variable 'expensive items' as a collection of items whose price is greater than 100. The implicit variable each item is used in the where clause to refer to each item object in the collection.

definitions
    set 'expensive items' to all items
        where the price of each item is more than 100;