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 021import java.util.ArrayList; 022 023/** 024 * 025 * @author Sebastian Bader 026 * 027 */ 028public class List extends Term { 029 private Term head; 030 private List tail; 031 032 public List() { 033 head = null; 034 tail = null; 035 } 036 037 public List(Term head, List tail) { 038 this.head = head; 039 this.tail = tail; 040 if (tail == null) 041 this.tail = new List(); 042 } 043 044 public static List compose(ArrayList<Term> content) { 045 if (content.isEmpty()) { 046 return new List(); 047 } else { 048 Term head = content.remove(0); 049 List body = compose(content); 050 return new List(head, body); 051 } 052 } 053 054 @Override 055 public boolean isGround() { 056 if (!head.isGround()) 057 return false; 058 return tail.isGround(); 059 } 060 061 062 @Override 063 public String toString() { 064 return "L["+((head != null)?head.toString()+"|"+tail:"")+"]"; 065 } 066 067 @Override 068 public String toPLString() { 069 return "["+((head != null)?head.toPLString()+"|"+tail.toPLString():"")+"]"; 070 } 071 072 @Override 073 public Term getInstance(Variable variable, Term term) { 074 if (head != null) { 075 Term newhead = head.getInstance(variable, term); 076 List newtail = (List) tail.getInstance(variable, term); 077 return new List(newhead, newtail); 078 } 079 return new List(null, null); 080 } 081 082 @Override 083 public boolean equals(Object obj) { 084 if (obj == null) 085 return false; 086 087 List list; 088 try { 089 list = (List) obj; 090 } catch (ClassCastException cce) { 091 return false; 092 } 093 094 if (head == null) { 095 if (list.head != null) 096 return false; 097 } else { 098 if (!head.equals(list.head)) 099 return false; 100 } 101 102 if (tail == null) { 103 return (list.tail == null); 104 } else { 105 return tail.equals(list.tail); 106 } 107 } 108 109 @Override 110 public int hashCode() { 111 if (head == null) 112 return 0; 113 return head.hashCode(); 114 } 115 116 @Override 117 public Object clone() { 118 return new List((Term) head.clone(), (List) tail.clone()); 119 } 120}