com.sri.ai.grinder.sgdpllt.library.number.LessThan Maven / Gradle / Ivy
/*
* Copyright (c) 2013, SRI International
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*
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package com.sri.ai.grinder.sgdpllt.library.number;
import static com.sri.ai.expresso.helper.Expressions.FALSE;
import static com.sri.ai.expresso.helper.Expressions.INFINITY;
import static com.sri.ai.expresso.helper.Expressions.MINUS_INFINITY;
import static com.sri.ai.expresso.helper.Expressions.TRUE;
import static com.sri.ai.expresso.helper.Expressions.isNumber;
import static com.sri.ai.expresso.helper.Expressions.makeSymbol;
import static com.sri.ai.util.Util.lessThan;
import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.grinder.api.Registry;
import com.sri.ai.grinder.sgdpllt.api.Context;
import com.sri.ai.grinder.sgdpllt.library.FunctorConstants;
import com.sri.ai.grinder.sgdpllt.rewriter.api.Simplifier;
/**
* @author braz
*/
@Beta
public class LessThan implements Simplifier {
@Override
public Expression applySimplifier(Expression expression, Context context) {
return simplify(expression, context);
}
/**
* Receives an application of {@link FunctorConstants.LESS_THAN} and evaluates it if possible.
* @param lessThanApplication
* @param registry TODO
* @return
*/
public static Expression simplify(Expression lessThanApplication, Registry registry) {
Expression result;
if (lessThanApplication.get(0).equals(lessThanApplication.get(1))) {
result = FALSE; // not less than itself
}
else if (isNumber(lessThanApplication.get(0)) && isNumber(lessThanApplication.get(1))) {
result = makeSymbol(lessThan(lessThanApplication.get(0).rationalValue(), lessThanApplication.get(1).rationalValue()));
}
else if ( lessThanApplication.get(0).equals(MINUS_INFINITY) && !lessThanApplication.get(1).equals(MINUS_INFINITY)) {
result = TRUE;
}
else if ( lessThanApplication.get(0).equals(INFINITY) && !lessThanApplication.get(1).equals(INFINITY)) {
result = FALSE;
}
else if (!lessThanApplication.get(0).equals(MINUS_INFINITY) && lessThanApplication.get(1).equals(MINUS_INFINITY)) {
result = FALSE;
}
else if (!lessThanApplication.get(0).equals(INFINITY) && lessThanApplication.get(1).equals(INFINITY)) {
result = TRUE;
}
else {
result = lessThanApplication;
}
return result;
}
}