AbstractFunction.java

/*
 * Vitry, copyright (C) Hans Hoglund 2011
 * 
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 * See COPYING.txt for details.
 */
package vitry.runtime;

import vitry.runtime.struct.Seq;


/**
 * This class implements most aspects of a function, except invocation.
 * Requires scope upon construction, however domain and range are mutable 
 * to allow for in-place type reconstruction.
 *
 * @author Hans Hoglund 
 */
abstract class AbstractFunction extends ConstructionPattern 
implements Function, Scope, TypableFunction
{
    final Env<Symbol, Object> environment;

    private Pattern domain;

    private Seq<Pattern> range;


    public AbstractFunction() {
        this(AbstractEnv.<Symbol, Object>empty());
    }

    public AbstractFunction(Scope scope) {
        this(scope.getValues(), null, null);
    }

    protected AbstractFunction(Env<Symbol, Object> env) {
        this(env, null, null);
    }

    protected AbstractFunction(Env<Symbol, Object> env, Pattern domain, Seq<Pattern> range) {
        this.environment = env;
        this.domain = domain;
        this.range = range;
    }


    public Object getValue(String name)
    {
        return getValue(Symbol.intern(name));
    }

    public Object getValue(Symbol name)
    {
        return environment.lookup(name);
    }

    public Env<Symbol, Object> getValues()
    {
        return this.environment;
    }

    public synchronized Pattern getDomain()
    {
        return domain;
    }

    public synchronized Seq<Pattern> getRange()
    {
        return range;
    }

    public synchronized void setDomain(Pattern domain)
    {
        this.domain = domain;
    }

    public synchronized void setRange(Seq<Pattern> range)
    {
        this.range = range;
    }

    public boolean isCompiled()
    {
        return true;
    }
    
    @Override
    public boolean eq(Function o)
    {
        return o == this;
    }

    @Override
    public boolean match(Function p)
    {
        return p == this;
    }

    public boolean eqFor(Pattern o)
    {
        return o.eq(this);
    }

    public boolean matchFor(Pattern p)
    {
        return p.match(this);
    }

    public boolean isInvertible()
    {
        return false;
    }

    public Pattern head()
    {
        return this.getDomain();
    }


    public Seq<Pattern> tail()
    {
        return this.getRange();
    }
    
    public boolean isNil()
    {
        return false;
    }

    public boolean hasTail()
    {
        return this.getRange() != null;
    }

    public String toString()
    {
        if (domain == null)
            return super.toString();
        if (range == null)
            return domain.toString();
        else
            return domain.toString() + " -> " + range.toString();
    }


    protected static int checkArity(int arity)
    {
        if (arity < VitryRuntime.MIN_ARITY || arity > VitryRuntime.MAX_ARITY)
            throw new IllegalArgumentException("Function must have arity a where "
                    + VitryRuntime.MIN_ARITY + " < a < " + VitryRuntime.MAX_ARITY);
        return arity;
    }


}