//tabstop=4
//*****************************************************************************/
// Project: jpl
//
// File: $Id: Compound.java,v 1.1 2004-08-27 20:27:56 vsc Exp $
// Date: $Date: 2004-08-27 20:27:56 $
// Author: Fred Dushin <fadushin@syr.edu>
//
//
// Description:
//
//
// -------------------------------------------------------------------------
// Copyright (c) 2004 Paul Singleton
// Copyright (c) 1998 Fred Dushin
// All rights reserved.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Library Public License for more details.
//*****************************************************************************/
package jpl;
import java.util.Map;
import jpl.fli.IntHolder;
import jpl.fli.Prolog;
import jpl.fli.StringHolder;
import jpl.fli.term_t;
//----------------------------------------------------------------------/
// Compound
/**
* A Compound represents a structured term,
* comprising a functor and arguments (Terms).
* Atom is a subclass of Compound, whose instances have zero arguments.
* Direct instances of Compound must have one or more arguments
* (it is an error to attempt to construct a Compound with zero args;
* a JPLException will be thrown).
* For example, this Java expression yields
* a representation of the term f(a):
* <pre>
* new Compound( "f", new Term[] { new Atom("a") } )
* </pre>
* Note the use of the "anonymous array" notation to denote the arguments
* (an anonymous array of Term).
* <br>
* Alternatively, construct the Term from Prolog source syntax:
* <pre>
* Util.textToTerm("f(a)")
* </pre>
* The <i>arity</i> of a Compound is the quantity of its arguments.
* Once constructed, neither the name, arity nor any argument of a Compound can be altered.
* <hr><i>
* Copyright (C) 2004 Paul Singleton<p>
* Copyright (C) 1998 Fred Dushin<p>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.<p>
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library Public License for more details.<p>
* </i><hr>
* @author Fred Dushin <fadushin@syr.edu>
* @version $Revision: 1.1 $
* @see jpl.Term
* @see jpl.Atom
*/
public class Compound extends Term {
//==================================================================/
// Attributes
//==================================================================/
/**
* the name of this Compound
*/
protected final String name;
/**
* the arguments of this Compound
*/
protected final Term[] args;
//==================================================================/
// Constructors
//==================================================================/
/**
* Creates a Compound with name but no args (i.e. an Atom).
*
* @param name the name of this Compound
* @param args the arguments of this Compound
*/
protected Compound(String name) {
if (name == null) {
throw new JPLException("jpl.Atom: cannot construct with null name");
}
this.name = name;
this.args = new Term[] {
};
}
/**
* Creates a Compound with name and args.
*
* @param name the name of this Compound
* @param args the arguments of this Compound
*/
public Compound(String name, Term[] args) {
if (name == null) {
throw new JPLException("jpl.Compound: cannot construct with null name");
}
if (args == null) {
throw new JPLException("jpl.Compound: cannot construct with null args");
}
if (args.length == 0) {
throw new JPLException("jpl.Compound: cannot construct with zero args");
}
this.name = name;
this.args = args;
}
//==================================================================/
// Methods (common)
//==================================================================/
/**
* Returns the ith argument (counting from 1) of this Compound;
* throws an ArrayIndexOutOfBoundsException if i is inappropriate.
*
* @return the ith argument (counting from 1) of this Compound
*/
public final Term arg(int i) {
return args[i - 1];
}
/**
* Tests whether this Compound's functor has (String) 'name' and 'arity'.
*
* @return whether this Compound's functor has (String) 'name' and 'arity'
*/
public final boolean hasFunctor(String name, int arity) {
return name.equals(name) && arity == args.length;
}
/**
* Returns the name (unquoted) of this Compound.
*
* @return the name (unquoted) of this Compound
*/
public final String name() {
return name;
}
/**
* Returns the arity (1+) of this Compound.
*
* @return the arity (1+) of this Compound
*/
public final int arity() {
return args.length;
}
/**
* Returns a prefix functional representation of a Compound of the form name(arg1,...),
* where each argument is represented according to its toString() method.
* <br>
* NB 'name' should be quoted iff necessary, and Term.toString(Term[]) is not
* really a Term method, more a utility...
*
* @return string representation of an Compound
*/
public String toString() {
return quotedName() + (args.length > 0 ? "(" + Term.toString(args) + ")" : "");
}
/**
* Two Compounds are equal if they are identical (same object) or their names and arities are equal and their
* respective arguments are equal.
*
* @param obj the Object to compare (not necessarily another Compound)
* @return true if the Object satisfies the above condition
*/
public final boolean equals(Object obj) {
return (this == obj || (obj instanceof Compound && name.equals(((Compound) obj).name) && Term.terms_equals(args, ((Compound) obj).args)));
}
public int type() {
return Prolog.COMPOUND;
}
public String typeName(){
return "Compound";
}
//==================================================================/
// Methods (protected)
//==================================================================/
/**
* Returns a quoted (iff necessary) form of the Atom's name, as understood by Prolog read/1
*
* @return a quoted form of the Atom's name, as understood by Prolog read/1
*/
protected String quotedName() {
return ((Atom) (new Query(new Compound("sformat", new Term[] { new Variable("S"), new Atom("~q"), new Compound(".", new Term[] { new Atom(this.name), new Atom("[]")})
})))
.oneSolution()
.get(
"S")).name;
}
//==================================================================/
// Methods (deprecated)
//==================================================================/
/**
* Returns the arguments of this Compound.
*
* @return the arguments of this Compound
* @deprecated
*/
public final Term[] args() {
return args;
}
/**
* Returns the ith argument (counting from 0) of this Compound.
*
* @return the ith argument (counting from 0) of this Compound
* @deprecated
*/
public final Term arg0(int i) {
return args[i];
}
/**
* Returns a debug-friendly representation of a Compound.
*
* @return a debug-friendly representation of a Compound
* @deprecated
*/
public String debugString() {
return "(Compound " + name + " " + Term.debugString(args) + ")";
}
//==================================================================/
// Converting JPL Terms to Prolog terms
//==================================================================/
/**
* To put a Compound in a term, we create a sequence of term_t
* references from the Term.terms_to_term_ts() method, and then
* use the Prolog.cons_functor_v() method to create a Prolog compound
* term.
*
* @param varnames_to_vars A Map from variable names to Prolog variables
* @param term A (previously created) term_t which is to be
* set to a Prolog term corresponding to the Term subtype
* (Atom, Variable, Compound, etc.) on which the method is invoked.
*/
protected final void put(Map varnames_to_vars, term_t term) {
Prolog.cons_functor_v(term, Prolog.new_functor(Prolog.new_atom(name), args.length), Term.putTerms(varnames_to_vars, args));
}
//==================================================================/
// Converting Prolog terms to JPL Terms
//==================================================================/
/**
* Converts the Prolog term in term_t (known to be a compound) to a JPL Compound.
* In this case, we create a list of Terms by calling Term.getTerm for each
* term_t reference we get from Prolog.get_arg
* (Not sure why we couldn't get a sequence from there, but...).<p>
*
* @param varnames_to_vars A Map from variable names to Prolog variables
* @param term The Prolog term to convert
* @return A new Compound
*/
protected static Term getTerm(Map varnames_to_vars, term_t term) {
// we need holders to get the term's name and arity back from the FLI:
StringHolder name_holder = new StringHolder();
IntHolder arity_holder = new IntHolder();
Prolog.get_name_arity(term, name_holder, arity_holder); // assume it succeeds
Term args[] = new Term[arity_holder.value];
for (int i = 1; i <= arity_holder.value; i++) {
term_t termi = Prolog.new_term_ref();
Prolog.get_arg(i, term, termi);
args[i - 1] = Term.getTerm(varnames_to_vars, termi);
}
return new Compound(name_holder.value, args);
}
//==================================================================/
// Computing Substitutions
//==================================================================/
/**
* Nothing needs to be done except to pass the buck to this Compound's args.
*
* @param varnames_to_Terms A Map from variable names to JPL Terms
* @param vars_to_Vars A Map from Prolog variables to JPL Variables
*/
protected final void getSubst(Map varnames_to_Terms, Map vars_to_Vars) {
Term.getSubsts(varnames_to_Terms, vars_to_Vars, args);
}
}
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