/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * This file is part of SimpleC.                                   *
 * See the file "SimpleC-LICENSE" for Copyright information and    *
 * the terms and conditions for copying, distribution and          *
 * modification of SimpleC.                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

package org.sablecc.simplec;


import java.util.*;

class Variable 
{
    static int next_number;
    final int number = next_number++;
    static LinkedList variables = new LinkedList();

    Type type;

    Variable parent = this;
    int rank = 0;
    LinkedList pending = new LinkedList();

    Variable(Type t)
    {
        type = t;

        variables.add(this);
    }

    Variable union(Variable var)
    {
        Variable x = ecr();
        Variable y = var.ecr();

        if(x == y)
        {
            return x;
        }

        if(x.rank > y.rank)
        {
            y.parent = x;

            return x;
        }

        x.parent = y;

        if(x.rank == y.rank)
        {
            y.rank++;
        }

        return y;
    }

    Variable ecr()
    {
        if(this != parent)
        {
            parent = parent.ecr();
        }

        return parent;
    }

    void setType(Type t)
    {
        Variable e = ecr();

        e.type = t;

        for(Iterator i = e.pending.iterator(); i.hasNext();)
        {
            e.join((Variable) i.next());
        }
    }

    void cjoin(Variable v)
    {
        Variable e1 = ecr();
        Variable e2 = v.ecr();

        if(e2.type == Bottom.instance)
        {
            e2.pending.add(e1);
        }
        else
        {
            e1.join(e2);
        }
    }

    void join(Variable v)
    {
        Variable e1 = ecr();
        Variable e2 = v.ecr();

        Type t1 = e1.type;
        Type t2 = e2.type;
        Variable e = e1.union(e2);

        if(t1 == Bottom.instance)
        {
            e.type = t2;

            if(t2 == Bottom.instance)
            {
                e1.pending.addAll(e2.pending);
                e.pending = e1.pending;
            }
            else
            {
                for(Iterator i = e1.pending.iterator(); i.hasNext();)
                {
                    e.join((Variable) i.next());
                }
            }
        }
        else
        {
            e.type = t1;

            if(t2 == Bottom.instance)
            {
                for(Iterator i = e2.pending.iterator(); i.hasNext();)
                {
                    e.join((Variable) i.next());
                }
            }
            else
            {
                t1.unify(t2);
            }
        }
    }

    public String toString()
    {
        return "T" + number + " = " + type;
    }
}