content: /*
   * Copyright (c) 2018, 2020, the Alpha Team.
   * All rights reserved.
   *
   * Additional changes made by Siemens.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1) Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2) Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package at.ac.tuwien.kr.alpha.core.grounder;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  import org.junit.jupiter.api.Test;
  
  import at.ac.tuwien.kr.alpha.api.programs.ASPCore2Program;
  import at.ac.tuwien.kr.alpha.api.programs.ProgramParser;
  import at.ac.tuwien.kr.alpha.api.programs.atoms.Atom;
  import at.ac.tuwien.kr.alpha.api.programs.atoms.BasicAtom;
  import at.ac.tuwien.kr.alpha.api.programs.terms.Term;
  import at.ac.tuwien.kr.alpha.api.programs.terms.VariableTerm;
  import at.ac.tuwien.kr.alpha.commons.programs.terms.Terms;
  import at.ac.tuwien.kr.alpha.commons.substitutions.Unifier;
  import at.ac.tuwien.kr.alpha.core.parser.ProgramParserImpl;
  
  public class UnifierTest extends SubstitutionTest {
  
  	@Test
  	public void extendUnifier() {
  		VariableTerm varX = Terms.newVariable("X");
  		VariableTerm varY = Terms.newVariable("Y");
  		Unifier sub1 = new Unifier();
  		sub1.put(varX, varY);
  		Unifier sub2 = new Unifier();
  		sub2.put(varY, Terms.newConstant("a"));
  
  		sub1.extendWith(sub2);
  		BasicAtom atom1 = parseAtom("p(X)");
  
  		Atom atomSubstituted = atom1.substitute(sub1);
  		assertEquals(Terms.newConstant("a"), atomSubstituted.getTerms().get(0));
  	}
  
  	@Test
  	public void mergeUnifierIntoLeft() {
  		VariableTerm varX = Terms.newVariable("X");
  		VariableTerm varY = Terms.newVariable("Y");
  		VariableTerm varZ = Terms.newVariable("Z");
  		Term constA = Terms.newConstant("a");
  		Unifier left = new Unifier();
  		left.put(varX, varY);
  		left.put(varZ, varY);
  		Unifier right = new Unifier();
  		right.put(varX, constA);
  		Unifier merged = Unifier.mergeIntoLeft(left, right);
  		assertEquals(constA, merged.eval(varY));
  		assertEquals(constA, merged.eval(varZ));
  	}
  
  	private BasicAtom parseAtom(String atom) {
  		ProgramParser programParser = new ProgramParserImpl();
  		ASPCore2Program program = programParser.parse(atom + ".");
  		return (BasicAtom) program.getFacts().get(0);
  	}
  }
  