org.eclipse.viatra.query.runtime.matchers.psystem

Interface IExpressionEvaluator

All Known Implementing Classes:

XBaseEvaluator

public interface IExpressionEvaluator

An expression evaluator is used to execute arbitrary Java code during pattern matching. In order to include the evaluation in the planning seemlessly it is expected from the evaluator implementors to report all used PVariables by name.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	evaluateExpression(IValueProvider provider) The expression evaluator code
java.lang.Iterable<java.lang.String>	getInputParameterNames() All input parameter names should be reported correctly.
java.lang.String	getShortDescription() A textual description of the expression.

Method Detail

getShortDescription

java.lang.String getShortDescription()

A textual description of the expression. Used only for debug purposes, but must not be null.

getInputParameterNames

java.lang.Iterable<java.lang.String> getInputParameterNames()

All input parameter names should be reported correctly.

evaluateExpression

java.lang.Object evaluateExpression(IValueProvider provider)
                             throws java.lang.Exception

The expression evaluator code

Parameters:

provider - the value provider is an engine-specific way of reading internal variable tuples to evaluate the expression with

Returns:

the result of the expression: in case of predicate evaluation the return value must be true or false; otherwise the result can be an arbitrary object. No null values should be returned.

Throws:

java.lang.Exception