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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.rankingexpression.rule;
import java.io.Serializable;
/**
* A mathematical operator
*
* @author bratseth
*/
public enum TruthOperator implements Serializable {
SMALLER("<") { public boolean evaluate(double x, double y) { return x<y; } },
SMALLEREQUAL("<=") { public boolean evaluate(double x, double y) { return x<=y; } },
EQUAL("==") { public boolean evaluate(double x, double y) { return x==y; } },
APPROX_EQUAL("~=") { public boolean evaluate(double x, double y) { return approxEqual(x,y); } },
LARGER(">") { public boolean evaluate(double x, double y) { return x>y; } },
LARGEREQUAL(">=") { public boolean evaluate(double x, double y) { return x>=y; } },
NOTEQUAL("!=") { public boolean evaluate(double x, double y) { return x!=y; } };
private final String operatorString;
TruthOperator(String operatorString) {
this.operatorString = operatorString;
}
/** Perform the truth operation on the input */
public abstract boolean evaluate(double x, double y);
@Override
public String toString() { return operatorString; }
public static TruthOperator fromString(String string) {
for (TruthOperator operator : values())
if (operator.toString().equals(string))
return operator;
throw new IllegalArgumentException("Illegal truth operator '" + string + "'");
}
private static boolean approxEqual(double x,double y) {
if (y < -1.0 || y > 1.0) {
x = Math.nextAfter(x/y, 1.0);
y = 1.0;
} else {
x = Math.nextAfter(x, y);
}
return x==y;
}
}
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