// Copyright 2004-2005 ASERT. Released under the Canoo Webtest license.
package com.canoo.webtest.util;
/**
* Evaluator is a callback interface for the Expression class.
* Objects wanting to define special values to be parsed in expressions
* should supply an Evaluator instance that converts a string value
* into it's double value.
* <p/>
* For example, to parse "2*(3-PI)", evaluate will be called with the value
* "PI", which should return the value Math.PI. The whole expression will then
* evaluate to 0.283
*
* @author Paul King
* @author Rob Nielsen
*/
public interface Evaluator
{
/**
* Evaluates a special string value.
*
* @param s the string to evaluate
* @return the double value of the string
* @throws IllegalArgumentException if there is a problem parsing the parameter
*/
double evaluate(String s);
}
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