com.sri.ai.grinder.sgdpllt.library.Associative Maven / Gradle / Ivy
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package com.sri.ai.grinder.sgdpllt.library;
import java.util.LinkedList;
import java.util.List;
import com.google.common.annotations.Beta;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.expresso.helper.Expressions;
/**
* @author braz
*/
@Beta
public class Associative {
/** A static version of associate when check for associative operator is done, with predicate indicating whether argument of same functor is to be associated. */
public static Expression associateWhenSureOperatorIsAssociative(Expression expression) {
Predicate alwaysTrue = Predicates.alwaysTrue();
Expression result = associateWhenSureOperatorIsAssociative(expression, alwaysTrue);
return result;
}
/** A static version of associate when check for associative operator is done, with predicate indicating whether argument of same functor is to be associated. */
public static Expression associateWhenSureOperatorIsAssociative(Expression expression, Predicate isAssociatable) {
if (expression.numberOfArguments() == 0) {
return expression;
}
List resultArguments = new LinkedList();
Expression functor = expression.getFunctor();
boolean change = false;
for (Expression argument : expression.getArguments()) {
if (argument.hasFunctor(functor) &&
argument.numberOfArguments() > 1 &&
isAssociatable.apply(argument)) {
resultArguments.addAll(argument.getArguments());
change = true;
}
else {
resultArguments.add(argument);
}
}
if (change) {
return Expressions.makeExpressionOnSyntaxTreeWithLabelAndSubTrees(functor, resultArguments);
}
return expression;
}
}