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/*
* Copyright (c) 2013, SRI International
* All rights reserved.
* Licensed under the The BSD 3-Clause License;
* you may not use this file except in compliance with the License.
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*
* http://opensource.org/licenses/BSD-3-Clause
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package com.sri.ai.grinder.sgdpllt.theory.base;
import static com.sri.ai.expresso.helper.Expressions.FALSE;
import static com.sri.ai.expresso.helper.Expressions.TRUE;
import static com.sri.ai.grinder.sgdpllt.theory.base.ConstantStepSolver.constantStepSolver;
import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.grinder.sgdpllt.api.Context;
import com.sri.ai.grinder.sgdpllt.api.StepSolver;
import com.sri.ai.grinder.sgdpllt.core.constraint.ContextSplitting;
/**
* A context-dependent problem step solver
* that simply decides whether a literal is true or not,
* producing boolean {@link Expression}.
*
* Note that this is different from {@link LiteralStepSolver}
* because that class produces a Java {@link Boolean} solution.
*
* @author braz
*
*/
@Beta
public class LiteralExpressionStepSolver implements StepSolver {
protected Expression literal;
public LiteralExpressionStepSolver(Expression literal) {
super();
this.literal = literal;
}
@Override
public LiteralExpressionStepSolver clone() {
try {
return (LiteralExpressionStepSolver) super.clone();
} catch (CloneNotSupportedException e) {
throw new Error("Trying to clone " + getClass() + " but cloning is not supported for this class.");
}
}
@Override
public StepSolver.Step step(Context context) {
ContextSplitting split = new ContextSplitting(literal, context);
switch (split.getResult()) {
case CONSTRAINT_IS_CONTRADICTORY:
return null;
case LITERAL_IS_TRUE:
return new Solution<>(TRUE);
case LITERAL_IS_FALSE:
return new Solution<>(FALSE);
case LITERAL_IS_UNDEFINED:
StepSolver ifTrue = constantStepSolver(TRUE);
StepSolver ifFalse = constantStepSolver(FALSE);
return new ItDependsOn(literal, split, ifTrue, ifFalse);
default:
throw new Error("Unrecognized splitting result.");
}
}
}