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1 package JSci.maths.symbolic;
2
3 import JSci.maths.*;
4 import JSci.maths.groups.*;
5 import java.util.*;
6
7 class Sum extends Expression {
8
9 private final List terms;
10
11 public Sum(Expression [] a) {
12 terms = Arrays.asList(a);
13 }
14
15 public Sum(List a) {
16 terms = a;
17 }
18
19 public Sum(Expression a,Expression b) {
20 terms = new ArrayList();
21 terms.add(a);
22 terms.add(b);
23 }
24
25 public String  toString() {
26 String r = "";
27 Expression f;
28 for (int j=0;j<terms.size();j++) {
29 if (j>0) r+="+";
30 f=(Expression)terms.get(j);
31 if (f.getPriority()<getPriority()) r+="("+f+")";
32 else r+=""+f;
33 }
34 return r;
35 }
36
37 public Expression differentiate(Variable x) {
38 List r = new ArrayList();
39 for (int j=0;j<terms.size();j++) {
40 r.add(((Expression)terms.get(j)).differentiate(x));
41 }
42 return new Sum(r);
43 }
44
45 public Expression evaluate() {
46 List t = new ArrayList();
48 for (int j=0;j<terms.size();j++) {
49 Expression f=((Expression)terms.get(j)).evaluate(); if (f instanceof Sum)
51 for (int k=0;k<((Sum)f).terms.size();k++)
52 t.add(((Sum)f).terms.get(k));
53 else t.add(f);
54 }
55 AbelianGroup.Member c = null;
57 List s = new ArrayList();
58 for (int j=0;j<t.size();j++) {
59 Expression f=(Expression)t.get(j);
60 if (f instanceof Constant) {
61 if (c==null) c=(AbelianGroup.Member)((Constant)f).getValue();
62 else c = c.add((AbelianGroup.Member)((Constant)f).getValue());
63 }
64 else s.add(f);
65 }
66 if (c!=null && ! (((AbelianGroup)(c.getSet())).isZero(c)))
67 s.add(new Constant(c));
68
69
72
74 if (s.size()==0) return new Constant(((AbelianGroup)getSet()).zero());
75 if (s.size()==1) return (Expression)s.get(0);
76 return new Sum(s);
77 }
78
79 protected int getPriority() {return 0;}
80
81 public Object getSet() { return ((Member)terms.get(0)).getSet(); }
82
83 }
84
85 |
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