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/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see .
 */

/*
 *    IfElseMacro.java
 *    Copyright (C) 2015 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core.expressionlanguage.common;

import weka.core.expressionlanguage.core.Node;
import weka.core.expressionlanguage.core.Macro;
import weka.core.expressionlanguage.core.MacroDeclarations;
import weka.core.expressionlanguage.core.SemanticException;
import weka.core.expressionlanguage.common.Primitives.BooleanExpression;
import weka.core.expressionlanguage.common.Primitives.DoubleExpression;
import weka.core.expressionlanguage.common.Primitives.StringExpression;

/**
 * A macro declaration exposing the ifelse function.

* * The ifelse macro can be used as follows:
* ifelse(condition, ifpart, elsepart)

* * Whith the following constraints:
*
    *
  • condition must be of boolean type
  • *
  • ifpart and elsepart must be of the same type
  • *
  • ifpart must be either of boolean, double or string type
  • *
* * Examples:
*
    *
  • ifelse(A < B, true, A = B)
  • *
  • ifelse(A = B, 4.0^2, 1/5)
  • *
  • ifelse(A > B, 'bigger', 'smaller')
  • *
* * @author Benjamin Weber ( benweber at student dot ethz dot ch ) * @version $Revision: 1000 $ */ public class IfElseMacro implements MacroDeclarations, Macro { private final static String IF_ELSE = "ifelse"; /** * Whether the macro is declared * * @param name name of the macro * @return whether the macro is declared */ @Override public boolean hasMacro(String name) { return IF_ELSE.equals(name); } /** * Tries to fetch the macro

* * The same invariant of {@link MacroDeclarations} applies here too. * * @param name name of the macro * @return a macro */ @Override public Macro getMacro(String name) { if (IF_ELSE.equals(name)) return this; throw new RuntimeException("Undefined Macro '" + name + "'!"); } /** * Evaluates the ifelse macro * * @param params the parameters * @return an AST (abstract syntax tree) node evaluating the ifelse function */ @Override public Node evaluate(Node... params) throws SemanticException { if (params.length != 3) throw new SemanticException("ifelse takes exactly 3 arguments!"); if (!(params[0] instanceof BooleanExpression)) throw new SemanticException("ifelse's first parameter must be boolean!"); if (params[1] instanceof BooleanExpression && params[2] instanceof BooleanExpression) { return new BooleanIfElse( (BooleanExpression) params[0], (BooleanExpression) params[1], (BooleanExpression) params[2] ); } else if (params[1] instanceof DoubleExpression && params[2] instanceof DoubleExpression) { return new DoubleIfElse( (BooleanExpression) params[0], (DoubleExpression) params[1], (DoubleExpression) params[2] ); } else if (params[1] instanceof StringExpression && params[2] instanceof StringExpression) { return new StringIfElse( (BooleanExpression) params[0], (StringExpression) params[1], (StringExpression) params[2] ); } throw new SemanticException("ifelse's second and third parameter must be doubles, booleans or Strings!"); } private static class DoubleIfElse implements DoubleExpression { private final BooleanExpression condition; private final DoubleExpression ifPart; private final DoubleExpression elsePart; public DoubleIfElse(BooleanExpression condition, DoubleExpression ifPart, DoubleExpression elsePart) { this.condition = condition; this.ifPart = ifPart; this.elsePart = elsePart; } @Override public double evaluate() { if (condition.evaluate()) return ifPart.evaluate(); return elsePart.evaluate(); } } private static class BooleanIfElse implements BooleanExpression { private final BooleanExpression condition; private final BooleanExpression ifPart; private final BooleanExpression elsePart; public BooleanIfElse(BooleanExpression condition, BooleanExpression ifPart, BooleanExpression elsePart) { this.condition = condition; this.ifPart = ifPart; this.elsePart = elsePart; } @Override public boolean evaluate() { if (condition.evaluate()) return ifPart.evaluate(); return elsePart.evaluate(); } } private static class StringIfElse implements StringExpression { private final BooleanExpression condition; private final StringExpression ifPart; private final StringExpression elsePart; public StringIfElse(BooleanExpression condition, StringExpression ifPart, StringExpression elsePart) { this.condition = condition; this.ifPart = ifPart; this.elsePart = elsePart; } @Override public String evaluate() { if (condition.evaluate()) return ifPart.evaluate(); return elsePart.evaluate(); } } }




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