erjang.ENil.java Source code

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Here is the source code for erjang.ENil.java

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/**
 * This file is part of Erjang - A JVM-based Erlang VM
 *
 * Copyright (c) 2009 by Trifork
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *  
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 **/

package erjang;

import java.nio.ByteBuffer;
import java.util.List;

import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

public class ENil extends ESeq {

    private static final Type ENIL_TYPE = Type.getType(ENil.class);
    private static final Type ERT_TYPE = Type.getType(ERT.class);

    public ENil() {
        super();
    }

    public boolean isNil() {
        return true;
    }

    public String stringValue() {
        return "";
    }

    @Override
    public EObject head() {
        throw new UnsupportedOperationException();
    }

    @Override
    public EList tail() {
        throw new UnsupportedOperationException();
    }

    public boolean collectIOList(List<ByteBuffer> out) {
        return true;
    }

    @Override
    public void collectCharList(CharCollector out) {
    }

    @Override
    public String toString() {
        return "[]";
    }

    @Override
    public ESeq cons(EObject h) {
        /*
        ESmall sm;
        if ((sm=h.testSmall()) != null && ((sm.value & ~0xff) == 0)) {
           return new EStringList((byte)sm.value, this);
        }
        */
        return new EList(h, this);
    }

    @Override
    public Type emit_const(MethodVisitor fa) {
        fa.visitFieldInsn(Opcodes.GETSTATIC, ERT_TYPE.getInternalName(), "NIL", ENIL_TYPE.getDescriptor());
        return ENIL_TYPE;
    }

    @Override
    public ECons testNonEmptyList() {
        return null;
    }

    @Override
    public ECons testCons() {
        return this;
    }

    public ENil testNil() {
        return this;
    }

    /* (non-Javadoc)
     * @see erjang.EObject#compare_same(erjang.EObject)
     */
    @Override
    int compare_same(EObject rhs) {
        if (rhs.testNil() != null)
            return 0;
        return -1;
    }

    @Override
    public void encode(EOutputStream eos) {
        eos.write_nil();
    }

    @Override
    public ESeq prepend(ESeq list) {
        return list;
    }

    @Override
    public boolean equalsExactly(EObject rhs) {
        return rhs.isNil();
    }

    @Override
    public boolean equals(EObject other) {
        return other.isNil();
    }

    @Override
    public boolean equals(Object other) {
        if (other instanceof EObject) {
            return ((EObject) other).isNil();
        } else {
            return false;
        }
    }

    @Override
    public int hashCode() {
        return 0;
    }
}