| package jp.ac.kobe_u.cs.prolog.builtin; |
| import jp.ac.kobe_u.cs.prolog.lang.*; |
| /** |
| * <code>atom_chars/2</code><br> |
| * @author Mutsunori Banbara (banbara@kobe-u.ac.jp) |
| * @author Naoyuki Tamura (tamura@kobe-u.ac.jp) |
| * @version 1.1 |
| */ |
| public class PRED_atom_chars_2 extends Predicate { |
| static SymbolTerm Nil = SymbolTerm.makeSymbol("[]"); |
| Term arg1, arg2; |
| |
| public PRED_atom_chars_2(Term a1, Term a2, Predicate cont) { |
| arg1 = a1; |
| arg2 = a2; |
| this.cont = cont; |
| } |
| |
| public PRED_atom_chars_2() {} |
| |
| public void setArgument(Term[] args, Predicate cont){ |
| arg1 = args[0]; |
| arg2 = args[1]; |
| this.cont = cont; |
| } |
| |
| public int arity() { return 2 ; } |
| |
| public String toString() { return "atom_chars(" + arg1 + "," + arg2 + ")"; } |
| |
| public Predicate exec(Prolog engine) { |
| engine.setB0(); |
| Term a1, a2; |
| a1 = arg1; |
| a2 = arg2; |
| |
| a1 = a1.dereference(); |
| a2 = a2.dereference(); |
| if (a1.isVariable()) { // atom_chars(-Atom, +CharList) |
| if (a2.isNil()) { |
| if (! a1.unify(SymbolTerm.makeSymbol(""), engine.trail)) |
| return engine.fail(); |
| return cont; |
| } else if (a2.isVariable()) { |
| throw new PInstantiationException(this, 2); |
| } else if (! a2.isList()) { |
| throw new IllegalTypeException(this, 2, "list", a2); |
| } |
| StringBuffer sb = new StringBuffer(); |
| Term x = a2; |
| while(! x.isNil()) { |
| if (x.isVariable()) |
| throw new PInstantiationException(this, 2); |
| if (! x.isList()) |
| throw new IllegalTypeException(this, 2, "list", a2); |
| Term car = ((ListTerm)x).car().dereference(); |
| if (car.isVariable()) |
| throw new PInstantiationException(this, 2); |
| if (! car.isSymbol() || ((SymbolTerm)car).name().length() != 1) |
| throw new IllegalTypeException(this, 2, "character", a2); |
| sb.append(((SymbolTerm)car).name()); |
| x = ((ListTerm)x).cdr().dereference(); |
| } |
| if (! a1.unify(SymbolTerm.makeSymbol(sb.toString()), engine.trail)) |
| return engine.fail(); |
| return cont; |
| } else if (a2.isNil() || a2.isVariable() || a2.isList()) { // atom_chars(+Atom, ?CharList) |
| if (! a1.isSymbol()) |
| throw new IllegalTypeException(this, 1, "atom", a1); |
| String s = ((SymbolTerm)a1).name(); |
| Term x = Nil; |
| for (int i=s.length(); i>0; i--) { |
| x = new ListTerm(SymbolTerm.makeSymbol(s.substring(i-1,i)), x); |
| } |
| if(! a2.unify(x, engine.trail)) |
| return engine.fail(); |
| return cont; |
| } else { |
| return engine.fail(); |
| } |
| } |
| } |