001/*
002 * $Id$
003 */
004
005package edu.jas.poly;
006
007
008import java.util.ArrayList;
009import java.util.Arrays;
010import java.util.Comparator;
011import java.util.List;
012
013import edu.jas.structure.RingElem;
014
015
016/**
017 * Ordered list of vectors of polynomials. Mainly for storage and printing /
018 * toString and conversions to other representations. Lists of polynomials in
019 * this list are sorted according to the head terms of the first column.
020 * @author Heinz Kredel
021 */
022
023public class OrderedModuleList<C extends RingElem<C>> extends ModuleList<C> {
024
025
026    /**
027     * Constructor.
028     * @param r polynomial ring factory.
029     * @param l list of list of polynomials.
030     */
031    public OrderedModuleList(GenPolynomialRing<C> r, List<List<GenPolynomial<C>>> l) {
032        super(r, sort(r, ModuleList.padCols(r, l)));
033    }
034
035
036    /**
037     * Comparison with any other object.
038     * @see java.lang.Object#equals(java.lang.Object)
039     */
040    @Override
041    @SuppressWarnings("unchecked")
042    // not jet working
043    public boolean equals(Object m) {
044        if (!super.equals(m)) {
045            return false;
046        }
047        OrderedModuleList<C> ml = null;
048        try {
049            ml = (OrderedModuleList<C>) m;
050        } catch (ClassCastException ignored) {
051        }
052        if (ml == null) {
053            return false;
054        }
055        // compare sorted lists, done already in super.equals()
056        return true;
057    }
058
059
060    /**
061     * Hash code for OrderedModuleList.
062     * @see java.lang.Object#hashCode()
063     */
064    @Override
065    public int hashCode() {
066        return super.hashCode();
067    }
068
069
070    /**
071     * Sort a list of vectors of polynomials with respect to the ascending order
072     * of the leading Exponent vectors of the first column. The term order is
073     * taken from the ring.
074     * @param r polynomial ring factory.
075     * @param l list of polynomial lists.
076     * @return sorted list of polynomial lists from l.
077     */
078    @SuppressWarnings({ "unchecked", "cast" })
079    public static <C extends RingElem<C>> List<List<GenPolynomial<C>>> sort(GenPolynomialRing<C> r,
080                    List<List<GenPolynomial<C>>> l) {
081        if (l == null) {
082            return l;
083        }
084        if (l.size() <= 1) { // nothing to sort
085            return l;
086        }
087        final Comparator<ExpVector> evc = r.tord.getAscendComparator();
088        Comparator<List<GenPolynomial<C>>> cmp = new Comparator<List<GenPolynomial<C>>>() {
089
090
091            public int compare(List<GenPolynomial<C>> l1, List<GenPolynomial<C>> l2) {
092                int c = 0;
093                for (int i = 0; i < l1.size(); i++) {
094                    GenPolynomial<C> p1 = l1.get(i);
095                    GenPolynomial<C> p2 = l2.get(i);
096                    ExpVector e1 = p1.leadingExpVector();
097                    ExpVector e2 = p2.leadingExpVector();
098                    if (e1 == e2) {
099                        continue;
100                    }
101                    if (e1 == null && e2 != null) {
102                        return -1;
103                    }
104                    if (e1 != null && e2 == null) {
105                        return 1;
106                    }
107                    if (e1 == null || e2 == null) { // for findbugs
108                        continue; // cannot happen
109                    }
110                    if (e1.length() != e2.length()) {
111                        if (e1.length() > e2.length()) {
112                            return 1;
113                        }
114                        return -1;
115                    }
116                    c = evc.compare(e1, e2);
117                    if (c != 0) {
118                        return c;
119                    }
120                }
121                return c;
122            }
123        };
124
125        List<GenPolynomial<C>>[] s = null;
126        try {
127            s = (List<GenPolynomial<C>>[]) new List[l.size()];
128            //System.out.println("s.length = " + s.length );
129            //s = l.toArray(s); does not work
130            //for ( int i = 0; i < l.size(); i++ ) {
131            //    s[i] = l.get(i);
132            //}
133            int i = 0;
134            for (List<GenPolynomial<C>> p : l) {
135                s[i++] = p;
136            }
137            Arrays.<List<GenPolynomial<C>>> sort(s, cmp);
138            return new ArrayList<List<GenPolynomial<C>>>(Arrays.<List<GenPolynomial<C>>> asList(s));
139        } catch (ClassCastException ok) {
140            System.out.println("Warning: polynomials not sorted");
141        }
142        return l; // unsorted
143    }
144
145}