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Java > Open Source Codes > org > lsmp > djep > groupJep > values > AlgebraicExtensionElement


1 /* @author rich
2  * Created on 09-Mar-2004
3  *
4  * This code is covered by a Creative Commons
5  * Attribution, Non Commercial, Share Alike license
6  * <a HREF="http://creativecommons.org/licenses/by-nc-sa/1.0">License</a>
7  */
8 package org.lsmp.djep.groupJep.values;
9
10 import org.lsmp.djep.groupJep.groups.AlgebraicExtension;
11
12 /**
13  * An element of the algrabraic extension K(t).
14  * a0 + a1 t + a(n-1) t^(n-1)
15  * where t is defined to be the the solution of a polynomial equation.
16  *
17  * @see AlgebraicExtension
18  * @author Rich Morris
19  * Created on 09-Mar-2004
20  */
21 public class AlgebraicExtensionElement extends FreeGroupElement {
22
23     AlgebraicExtension ae;
24
25     /**
26      * An element of the algrabraic extension K(t).
27      * a0 + a1 t + a(n-1) t^(n-1)
28      * where t is defined to be the the solution of a polynomial equation.
29      * If the degree of the polynomial specified by coeffs is greater
30      * than n then the polynomial will be reduced by using
31      * the equation t^n = .....
32      * @param the algebraic extension.
33      * @param coeffs array of coeficients for this algebraic number. c0 + c1 t + ... + cn t^n
34      */
35     public AlgebraicExtensionElement(AlgebraicExtension K, Number JavaDoc coeffs[])
36     {
37         super(K,coeffs);
38         this.ae = K;
39         int deg_p = ae.getPoly().getDegree();
40         while(this.getCoeffs().length > deg_p)
41         {
42             Polynomial poly2 = ae.getSubsPoly();
43             int deg_c = this.getCoeffs().length-1;
44             // coeffs = (a_m s^(m-n)+...+a_n) s^n + (a_(n-1) s^(n-1)+...+a_0)
45 // = p1 * s^n + p2;
46 // = p2 - p1 * q;
47 Number JavaDoc p1Coeffs[] = new Number JavaDoc[deg_c-deg_p+1];
48             Number JavaDoc p2Coeffs[] = new Number JavaDoc[deg_p];
49             System.arraycopy(this.getCoeffs(),deg_p,p1Coeffs,0,deg_c-deg_p+1);
50             System.arraycopy(this.getCoeffs(),0,p2Coeffs,0,deg_p);
51             Polynomial p1 = new Polynomial(ae.getBaseRing(),ae.getPoly().getSymbol(),p1Coeffs);
52             Polynomial p2 = new Polynomial(ae.getBaseRing(),ae.getPoly().getSymbol(),p2Coeffs);
53             Polynomial p3 = p1.mul(poly2);
54             Polynomial p4 = p3.add(p2);
55             super.setCoeffs(p4.getCoeffs());
56         }
57     }
58
59     /** sub classes should overright this to make the correct type. */
60     protected Polynomial valueOf(Number JavaDoc lcoeffs[])
61     {
62         AlgebraicExtensionElement g = new AlgebraicExtensionElement(ae,lcoeffs);
63         return g;
64     }
65 }
66
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