001
002/*
003 * $Id: Monomial.java 5997 2020-03-17 15:34:31Z kredel $
004 */
005
006package edu.jas.poly;
007
008
009import java.util.Map;
010
011import edu.jas.structure.ElemFactory;
012// import edu.jas.structure.RingFactory;
013import edu.jas.structure.Element;
014import edu.jas.structure.RingElem;
015
016
017/**
018 * Monomial class. Represents pairs of exponent vectors and coefficients.
019 * Adaptor for Map.Entry.
020 * @author Heinz Kredel
021 */
022public final class Monomial<C extends RingElem<C>> implements Element<Monomial<C>> {
023
024
025    /**
026     * Exponent of monomial.
027     */
028    public final ExpVector e;
029
030
031    /**
032     * Coefficient of monomial.
033     */
034    public final C c;
035
036
037    /**
038     * Constructor of monomial.
039     * @param me a MapEntry.
040     */
041    public Monomial(Map.Entry<ExpVector, C> me) {
042        this(me.getKey(), me.getValue());
043    }
044
045
046    /**
047     * Constructor of monomial.
048     * @param e exponent.
049     * @param c coefficient.
050     */
051    public Monomial(ExpVector e, C c) {
052        this.e = e;
053        this.c = c;
054    }
055
056
057    /**
058     * Getter for exponent.
059     * @return exponent.
060     */
061    public ExpVector exponent() {
062        return e;
063    }
064
065
066    /**
067     * Getter for coefficient.
068     * @return coefficient.
069     */
070    public C coefficient() {
071        return c;
072    }
073
074
075    /**
076     * Clone this Element.
077     * @return Creates and returns a copy of this Element.
078     */
079    public Monomial<C> copy() {
080        return new Monomial<C>(e, c);
081    }
082
083
084    /**
085     * String representation of Monomial.
086     * @see java.lang.Object#toString()
087     */
088    @Override
089    public String toString() {
090        return c.toString() + " " + e.toString();
091    }
092
093
094    /**
095     * Script representation of Monomial.
096     * @see edu.jas.structure.Element#toScript()
097     */
098    @Override
099    public String toScript() {
100        if (c.isZERO()) {
101            return "0";
102        }
103        StringBuffer sb = new StringBuffer();
104        if (!c.isONE()) {
105            sb.append(c.toScript());
106            if (e.signum() != 0) {
107                sb.append(" * ");
108            }
109        }
110        sb.append(e.toScript());
111        return sb.toString();
112    }
113
114
115    /**
116     * Get a scripting compatible string representation of the factory.
117     * @return script compatible representation for this ElemFactory.
118     * @see edu.jas.structure.Element#toScriptFactory()
119     */
120    @Override
121    public String toScriptFactory() {
122        // Python and Ruby case
123        return ""; // TODO
124    }
125
126
127    /**
128     * Get the corresponding element factory.
129     * @return null, factory for this Element.
130     * @see edu.jas.structure.Element#factory()
131     */
132    public ElemFactory<Monomial<C>> factory() {
133        return null; // TODO
134        //return new GenPolynomialRing<C>((RingFactory<C>)c.factory(), e.length());
135    }
136
137
138    /**
139     * Comparison with any other object.
140     * @see java.lang.Object#equals(java.lang.Object)
141     */
142    @Override
143    @SuppressWarnings("unchecked")
144    public boolean equals(Object B) {
145        if (!(B instanceof Monomial)) {
146            return false;
147        }
148        Monomial<C> b = (Monomial<C>) B;
149        return (compareTo(b) == 0);
150    }
151
152
153    /**
154     * hashCode.
155     * @see java.lang.Object#hashCode()
156     */
157    @Override
158    public int hashCode() {
159        int h = e.hashCode();
160        h = (h << 4) + c.hashCode();
161        return h;
162    }
163
164
165    /**
166     * Monomial comparison.
167     * @param S Monomial.
168     * @return SIGN(this-S).
169     */
170    @Override
171    public int compareTo(Monomial<C> S) {
172        if (S == null) {
173            return 1;
174        }
175        int s = e.compareTo(S.e);
176        if (s != 0) {
177            return s;
178        }
179        return c.compareTo(S.c);
180    }
181
182}