setmn.java

JAVA在编译原理上的应用。

package lolo.scans;

/** A recognizer class to scan for many characters from a set of characters. 
 *
 * @author <a href="http://www.inf.uos.de/bernd" target="_blank">Bernd K&uuml;hl</a>
           (<a href="mailto:[e-mail]">[e-mail]</a>)
 */
public class SetMN extends Set {
    /** The lower limit. */
    protected final int m;
    /** The upper limit. */
    protected final int n;
    /** Constructs a recognizer which scans at least <tt>m</tt> and at most <tt>n</tt> characters.
     * If <tt>inside</tt> is <tt>true</tt> the characters have to be inside <tt>set</tt>,
     * else they have to be oustide of <tt>set</tt>.
     *
     * @param set the set of characters.
     * @param inside marks if the symbol characters have to be inside or outside <tt>set</tt>.
     * @param m the minimal number of characters.
     * @param n the maximum number of characters.
     */
    public SetMN(String set, boolean inside, int m, int n) throws IllegalArgumentException {
        super(set, inside);
        if (m < 1)
            throw new IllegalArgumentException("m < 1");
        if (n < m)
            throw new IllegalArgumentException("n <= m");
        this.m = m;
        this.n = n;
    }
    
    /** Counts the current number of recognized characters. */
    protected transient int jog;
    public void reset() {
        jog = 0;
    }
    
    public State nextChar(char ch) {
        jog ++;
        boolean b = inside ? set.indexOf(ch) >= 0 : set.indexOf(ch) < 0;
        return stateObject.set(
            b && jog < n,	// more
            b && jog >= m	// found
        );
    }
    /** Indicates whether some other object is &quot;equal to&quot; this one.
     * 
     * @return whether some other object is &quot;equal to&quot; this one.
     */
    public boolean equals(Object o) {
        if (o == null || !(o instanceof SetMN)) return false;
        if (this == o) return true;
        SetMN setmn = (SetMN) o;
        return setmn.m == m && setmn.n == n && setmn.inside == inside && setmn.set.equals(set);
    }
    /** Returns a hash code value for this object.
     *
     * @return a hash code value for this object.
     */
    public int hashCode() {
        return set.hashCode()+
            new Integer(m).hashCode()+
            new Integer(n).hashCode()+
            new Boolean(inside).hashCode();
    }
    
    /** Returns a string representation of the object.
     *
     * @return a string representation of the object.
     */
    public String toString() {
        return getClass().getName()+"["+set+","+inside+","+m+","+n+"]";
    }
}