weka.core.expressionlanguage.common.IfElseMacro Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of weka-stable Show documentation
Show all versions of weka-stable Show documentation
The Waikato Environment for Knowledge Analysis (WEKA), a machine
learning workbench. This is the stable version. Apart from bugfixes, this version
does not receive any other updates.
/*
* 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 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();
}
}
}