001/** 002 * Copyright (C) 2007 - 2016, Jens Lehmann 003 * 004 * This file is part of DL-Learner. 005 * 006 * DL-Learner is free software; you can redistribute it and/or modify 007 * it under the terms of the GNU General Public License as published by 008 * the Free Software Foundation; either version 3 of the License, or 009 * (at your option) any later version. 010 * 011 * DL-Learner is distributed in the hope that it will be useful, 012 * but WITHOUT ANY WARRANTY; without even the implied warranty of 013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 014 * GNU General Public License for more details. 015 * 016 * You should have received a copy of the GNU General Public License 017 * along with this program. If not, see <http://www.gnu.org/licenses/>. 018 */ 019package org.dllearner.prolog; 020 021/** 022 * 023 * @author Sebastian Bader 024 * 025 */ 026public class Literal { 027 private Atom atom; 028 private boolean positive; 029 030 public Literal(Atom atom, boolean state) { 031 this.atom = atom; 032 this.positive = state; 033 } 034 035 public Atom getAtom() { 036 return atom; 037 } 038 039 public boolean isPositive() { 040 return positive; 041 } 042 043 public boolean isGround() { 044 return atom.isGround(); 045 } 046 047 public Literal getInstance(Variable variable, Term term) { 048 return new Literal(atom.getInstance(variable, term), positive); 049 } 050 051 @Override 052 public String toString() { 053 return (positive?"+":"-")+atom.toString(); 054 } 055 056 public String toPLString() { 057 return (positive?"":"not ")+atom.toPLString(); 058 } 059 060 @Override 061 public boolean equals(Object obj) { 062 if (obj == null) 063 return false; 064 065 Literal l; 066 067 try { 068 l = (Literal) obj; 069 } catch (ClassCastException cce) { 070 return false; 071 } 072 073 if (positive != l.positive) 074 return false; 075 076 return atom.equals(l.atom); 077 } 078 079 @Override 080 public int hashCode() { 081 return atom.hashCode() * (positive?1:2); 082 } 083}