org.armedbear.lisp.Binding Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of abcl Show documentation
Common Lisp implementation running on the JVM
There is a newer version: 1.9.2
/*
 * Binding.java
 *
 * Copyright (C) 2002-2005 Peter Graves
 * $Id$
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obligated to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */

package org.armedbear.lisp;

/** Used by the environment to capture different kinds of bindings:
 * tags, blocks, functions and variables.
 *
 */
// Package accessibility.
final class Binding
{
    /** The symbol in case of a variable, block, symbol-macro or
     * non-SETF function binding, the tag (symbol or
     * integer) in case of a tag binding or the cons
     * in case of a SETF function binding
     */
    final LispObject symbol;

    /** Used only for tags and blocks. Refers to the
     * defining environment.
     *
     */
    Environment env = null;

    /** The value bound.
     *
     * In case of a block binding, it holds the block identifier to be used
     * with the Return to be thrown.
     *
     * In case of a tagbody, it holds the tail subforms of the tagbody, of
     * which the tag is the first subform.
     *
     * In case of a function binding, it holds the function object.
     *
     * In case of a variable binding, it holds the value associated with the
     * variable, unless specialp is true.
     *
     * In case of a symbol macro binding, holds the SymbolMacro instance
     * holding the macro's expansion.
     */
    LispObject value;

    /** Only used for variable bindings. Indicates whether or not the value
     * should be retrieved from the dynamic environment or from this binding.
     */
    boolean specialp;
    final Binding next;

    Binding(LispObject symbol, LispObject value, Binding next)
    {
        this.symbol = symbol;
        this.value = value;
        this.next = next;
    }

    Binding(LispObject symbol, Environment env,
            LispObject value, Binding next)
    {
        this(symbol, value, next);
        this.env = env;
    }
}