UnionFindItem.java

package de.skuzzle.polly.core.parser.ast.declarations.types.unification;


class UnionFindItem<E> {
    final E element;
    UnionFindItem<E> parent;
    
    
    
    public UnionFindItem(E element) {
        this.element = element;
        this.parent = this;
    }
    
    
    
    public boolean isRoot() {
        return this.parent == this;
    }
    
    
    
    public E getValue() {
        return this.element;
    }
    
    
    
    public UnionFindItem<E> newChild(E value) {
        final UnionFindItem<E> result = new UnionFindItem<E>(value);
        result.mergeInto(this);
        return result;
    }
    
    
    
    public UnionFindItem<E> root() {
        UnionFindItem<E> root = this.parent;
        while (root != root.parent) root = root.parent;
        
        UnionFindItem<E> current = this;
        while (current != root) {
            final UnionFindItem<E> temp = current.parent;
            current.parent = root;
            current = temp;
        }
        return root;
    }
    
    
    
    /**
     * Merges to items by setting this item's root to the root of the provided
     * item.  
     * @param other The item to merge with.
     * @return The new root item (which is the root of <tt>other</tt>
     */
    public UnionFindItem<E> mergeInto(UnionFindItem<E> other) {
        final UnionFindItem<E> myRoot = this.root();
        final UnionFindItem<E> otherRoot = other.root();
        myRoot.parent = otherRoot;
        return otherRoot;
    }
}