1 | /* emacs edit mode for this file is -*- C++ -*- */ |
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2 | /* $Id: cf_ops.cc,v 1.3 1997-07-19 08:09:28 schmidt Exp $ */ |
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3 | |
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4 | #include <config.h> |
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5 | |
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6 | #include "assert.h" |
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7 | |
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8 | #include "cf_defs.h" |
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9 | #include "canonicalform.h" |
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10 | #include "cf_iter.h" |
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11 | |
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12 | CanonicalForm |
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13 | psr( const CanonicalForm &f, const CanonicalForm &g, const Variable & x ) |
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14 | { |
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15 | return ( power( LC(g,x), degree(f,x)-degree(g,x)+1 ) * f ) % g; |
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16 | } |
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17 | |
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18 | CanonicalForm |
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19 | psq( const CanonicalForm &f, const CanonicalForm &g, const Variable & x ) |
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20 | { |
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21 | return ( power( LC(g,x), degree(f,x)-degree(g,x)+1 ) * f ) / g; |
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22 | } |
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23 | |
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24 | void |
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25 | psqr( const CanonicalForm &f, const CanonicalForm &g, CanonicalForm &q, CanonicalForm &r, const Variable& x ) |
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26 | { |
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27 | divrem( power( LC(g,x), degree(f,x)-degree(g,x)+1 ) * f, g, q, r ); |
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28 | } |
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29 | |
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30 | static void swapvar_rec ( const CanonicalForm &f, CanonicalForm &result, const CanonicalForm &term ); |
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31 | |
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32 | static void swapvar_between ( const CanonicalForm &f, CanonicalForm &result, const CanonicalForm &term, int expx2 ); |
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33 | |
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34 | static Variable sv_x1, sv_x2; |
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35 | |
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36 | CanonicalForm |
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37 | swapvar ( const CanonicalForm &f, const Variable &x1, const Variable &x2 ) |
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38 | { |
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39 | ASSERT( x1.level() > 0 && x2.level() > 0, "cannot swap algebraic Variables" ); |
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40 | if ( f.inCoeffDomain() || x1 == x2 || ( x1 > f.mvar() && x2 > f.mvar() ) ) |
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41 | return f; |
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42 | else { |
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43 | CanonicalForm result = 0; |
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44 | if ( x1 > x2 ) { |
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45 | sv_x1 = x2; sv_x2 = x1; |
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46 | } |
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47 | else { |
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48 | sv_x1 = x1; sv_x2 = x2; |
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49 | } |
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50 | if ( f.mvar() < sv_x2 ) |
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51 | swapvar_between( f, result, 1, 0 ); |
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52 | else |
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53 | swapvar_rec( f, result, 1 ); |
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54 | return result; |
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55 | } |
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56 | } |
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57 | |
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58 | void |
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59 | swapvar_rec ( const CanonicalForm &f, CanonicalForm &result, const CanonicalForm &term ) |
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60 | { |
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61 | if ( f.inCoeffDomain() || f.mvar() < sv_x1 ) |
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62 | result += term * f; |
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63 | else if ( f.mvar() == sv_x2 ) |
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64 | for ( CFIterator i = f; i.hasTerms(); i++ ) |
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65 | swapvar_between( i.coeff(), result, term, i.exp() ); |
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66 | else if ( f.mvar() < sv_x2 ) |
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67 | swapvar_between( f, result, term, 0 ); |
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68 | else |
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69 | for ( CFIterator i = f; i.hasTerms(); i++ ) |
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70 | swapvar_rec( i.coeff(), result, term*power( f.mvar(), i.exp() ) ); |
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71 | } |
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72 | |
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73 | void |
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74 | swapvar_between ( const CanonicalForm &f, CanonicalForm &result, const CanonicalForm &term, int expx2 ) |
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75 | { |
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76 | if ( f.inCoeffDomain() || f.mvar() < sv_x1 ) |
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77 | result += term * power( sv_x1, expx2 ) * f; |
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78 | else if ( f.mvar() == sv_x1 ) |
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79 | for ( CFIterator i = f; i.hasTerms(); i++ ) |
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80 | result += power( sv_x2, i.exp() ) * term * i.coeff() * power( sv_x1, expx2 ); |
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81 | else |
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82 | for ( CFIterator i = f; i.hasTerms(); i++ ) |
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83 | swapvar_between( i.coeff(), result, term*power( f.mvar(), i.exp() ), expx2 ); |
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84 | } |
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85 | |
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86 | CanonicalForm |
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87 | apply ( const CanonicalForm & f, void (*mf)( CanonicalForm &, int & ) ) |
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88 | { |
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89 | if ( f.inCoeffDomain() ) { |
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90 | int exp = 0; |
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91 | CanonicalForm result; |
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92 | mf( result, exp ); |
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93 | ASSERT( exp == 0, "illegal result, do not know what variable to use" ); |
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94 | return result; |
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95 | } |
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96 | else { |
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97 | CanonicalForm result, coeff; |
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98 | CFIterator i; |
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99 | int exp; |
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100 | Variable x = f.mvar(); |
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101 | for ( i = f; i.hasTerms(); i++ ) { |
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102 | coeff = i.coeff(); |
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103 | exp = i.exp(); |
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104 | mf( coeff, exp ); |
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105 | if ( ! coeff.isZero() ) |
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106 | result += power( x, exp ) * coeff; |
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107 | } |
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108 | return result; |
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109 | } |
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110 | } |
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111 | |
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112 | void |
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113 | degreesRec ( const CanonicalForm & f, int * degs ) |
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114 | { |
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115 | if ( ! f.inCoeffDomain() ) { |
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116 | int level = f.level(); |
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117 | int deg = f.degree(); |
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118 | if ( degs[level] < deg ) |
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119 | degs[level] = f.degree(); |
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120 | for ( CFIterator i = f; i.hasTerms(); i++ ) |
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121 | degreesRec( i.coeff(), degs ); |
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122 | } |
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123 | } |
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124 | |
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125 | int * |
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126 | degrees ( const CanonicalForm & f, int * degs ) |
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127 | { |
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128 | if ( f.inCoeffDomain() ) |
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129 | return 0; |
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130 | else { |
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131 | int level = f.level(); |
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132 | if ( degs == 0 ) |
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133 | degs = new int[level+1]; |
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134 | for ( int i = 0; i <= level; i++ ) |
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135 | degs[i] = 0; |
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136 | degreesRec( f, degs ); |
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137 | return degs; |
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138 | } |
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139 | } |
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140 | |
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141 | CanonicalForm |
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142 | mapdomain ( const CanonicalForm & f, CanonicalForm (*mf)( const CanonicalForm & ) ) |
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143 | { |
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144 | if ( f.inCoeffDomain() ) |
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145 | return mf( f ); |
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146 | else { |
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147 | CanonicalForm result = 0; |
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148 | CFIterator i; |
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149 | Variable x = f.mvar(); |
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150 | for ( i = f; i.hasTerms(); i++ ) |
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151 | result += power( x, i.exp() ) * mapdomain( i.coeff(), mf ); |
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152 | return result; |
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153 | } |
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154 | } |
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155 | |
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156 | int |
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157 | totaldegree ( const CanonicalForm & f ) |
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158 | { |
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159 | if ( f.isZero() ) |
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160 | return -1; |
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161 | else if ( f.inCoeffDomain() ) |
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162 | return 0; |
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163 | else { |
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164 | CFIterator i; |
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165 | int cdeg = 0, dummy; |
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166 | for ( i = f; i.hasTerms(); i++ ) |
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167 | if ( (dummy = totaldegree( i.coeff() ) + i.exp()) > cdeg ) |
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168 | cdeg = dummy; |
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169 | return cdeg; |
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170 | } |
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171 | } |
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172 | |
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173 | |
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174 | int |
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175 | totaldegree ( const CanonicalForm & f, const Variable & v1, const Variable & v2 ) |
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176 | { |
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177 | if ( f.isZero() ) |
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178 | return -1; |
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179 | else if ( v1 > v2 ) |
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180 | return 0; |
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181 | else if ( f.inCoeffDomain() ) |
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182 | return 0; |
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183 | else if ( f.mvar() < v1 ) |
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184 | return 0; |
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185 | else if ( f.mvar() == v1 ) |
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186 | return f.degree(); |
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187 | else if ( f.mvar() > v2 ) { |
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188 | CFIterator i; |
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189 | int cdeg = 0, dummy; |
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190 | for ( i = f; i.hasTerms(); i++ ) |
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191 | if ( (dummy = totaldegree( i.coeff(), v1, v2 )) > cdeg ) |
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192 | cdeg = dummy; |
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193 | return cdeg; |
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194 | } |
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195 | else { |
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196 | CFIterator i; |
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197 | int cdeg = 0, dummy; |
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198 | for ( i = f; i.hasTerms(); i++ ) |
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199 | if ( (dummy = totaldegree( i.coeff(), v1, v2 ) + i.exp()) > cdeg ) |
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200 | cdeg = dummy; |
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201 | return cdeg; |
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202 | } |
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203 | } |
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204 | |
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205 | //{{{ CanonicalForm resultant( const CanonicalForm & f, const CanonicalForm & g, const Variable & x ) |
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206 | //{{{ docu |
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207 | // |
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208 | // resultant() - return resultant of f and g with respect to x. |
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209 | // |
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210 | // We calculate the resultant using a subresultant PSR. |
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211 | // |
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212 | // flipFactor: Res(f, g) = flipFactor * Res(g, f) |
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213 | // F, G: f and g with x as main variable |
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214 | // pi, pi1, pi2: used to compute PSR |
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215 | // delta: |
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216 | // bi, Hi: |
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217 | // |
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218 | //}}} |
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219 | CanonicalForm |
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220 | resultant( const CanonicalForm & f, const CanonicalForm & g, const Variable & x ) |
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221 | { |
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222 | CanonicalForm Hi, bi, pi, pi1, pi2, F, G; |
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223 | int delta, flipFactor; |
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224 | Variable v; |
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225 | |
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226 | ASSERT( x.level() > 0, "cannot calculate resultant in respect to algebraic variables" ); |
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227 | |
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228 | // some checks on triviality. We will not use degree( v ) |
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229 | // here because this may involve variable swapping. |
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230 | if ( f.isZero() || g.isZero() ) |
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231 | return 0; |
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232 | if ( f.mvar() < x ) |
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233 | return power( f, g.degree( x ) ); |
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234 | if ( g.mvar() < x ) |
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235 | return power( g, f.degree( x ) ); |
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236 | |
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237 | // make x main variale |
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238 | if ( f.mvar() > x || g.mvar() > x ) { |
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239 | if ( f.mvar() > g.mvar() ) |
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240 | v = f.mvar(); |
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241 | else |
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242 | v = g.mvar(); |
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243 | F = swapvar( f, v, x ); |
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244 | G = swapvar( g, v, x ); |
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245 | } |
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246 | else { |
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247 | v = x; |
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248 | F = f; |
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249 | G = g; |
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250 | } |
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251 | // at this point, we have to calculate resultant( F, G, v ) |
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252 | // where v is equal to or greater than the main variables |
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253 | // of F and G |
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254 | |
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255 | // trivial case: F or G in R. Swapping will not occur |
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256 | // when calling degree( v ). |
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257 | if ( F.degree( v ) < 1 ) |
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258 | return power( f, G.degree( v ) ); |
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259 | if ( G.degree( v ) < 1 ) |
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260 | return power( g, F.degree( v ) ); |
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261 | |
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262 | // start the pseudo remainder sequence |
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263 | if ( F.degree( v ) >= G.degree( v ) ) { |
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264 | pi = F; pi1 = G; |
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265 | flipFactor = 1; |
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266 | } |
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267 | else { |
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268 | if ( (F.degree( v ) * G.degree( v )) % 2 ) |
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269 | flipFactor = -1; |
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270 | else |
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271 | flipFactor = 1; |
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272 | pi = G; pi1 = F; |
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273 | } |
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274 | |
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275 | delta = degree( pi, v ) - degree( pi1, v ); |
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276 | Hi = power( LC( pi1, v ), delta ); |
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277 | |
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278 | // Ist hier nicht if und else zweig vertauscht ??? |
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279 | if ( (delta+1) % 2 ) |
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280 | bi = 1; |
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281 | else |
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282 | bi = -1; |
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283 | |
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284 | // Ist pi1.isZero vielleich schneller ??? |
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285 | while ( degree( pi1, v ) >= 0 ) { |
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286 | pi2 = psr( pi, pi1, v ); |
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287 | pi2 = pi2 / bi; |
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288 | pi = pi1; pi1 = pi2; |
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289 | if ( degree( pi1, v ) >= 0 ) { |
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290 | delta = degree( pi, v ) - degree( pi1, v ); |
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291 | |
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292 | // Ist hier nicht if und else zweig vertauscht ??? |
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293 | if ( (delta+1) % 2 ) |
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294 | bi = LC( pi, v ) * power( Hi, delta ); |
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295 | else |
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296 | bi = -LC( pi, v ) * power( Hi, delta ); |
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297 | |
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298 | // Was ist f"ur delta == 0 ??? |
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299 | Hi = power( LC( pi1, v ), delta ) / power( Hi, delta-1 ); |
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300 | } |
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301 | } |
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302 | |
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303 | // f and g have non-trivial common divisor |
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304 | // if ( degree( pi, v ) > 0 ) |
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305 | // return 0; |
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306 | |
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307 | // undo variable swap |
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308 | if ( v == x ) |
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309 | // Gibt man hier nicht den letzten Rest der PSR zur"uck |
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310 | // und nicht den Korrekturterm Hi ??? |
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311 | return Hi * flipFactor; |
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312 | else |
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313 | return swapvar( Hi, v, x ) * flipFactor; |
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314 | } |
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315 | //}}} |
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316 | |
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317 | static CanonicalForm |
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318 | cden ( const CanonicalForm & f ) |
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319 | { |
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320 | if ( f.inCoeffDomain() ) |
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321 | return f.den(); |
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322 | else { |
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323 | CFIterator i; |
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324 | CanonicalForm cd = 1; |
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325 | for ( i = f; i.hasTerms(); i++ ) |
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326 | cd = lcm( cd, cden( i.coeff() ) ); |
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327 | return cd; |
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328 | } |
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329 | } |
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330 | |
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331 | CanonicalForm |
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332 | common_den ( const CanonicalForm & f ) |
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333 | { |
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334 | if ( getCharacteristic() == 0 && isOn( SW_RATIONAL ) ) { |
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335 | Off( SW_RATIONAL ); |
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336 | CanonicalForm cd = cden( f ); |
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337 | On( SW_RATIONAL ); |
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338 | return cd; |
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339 | } |
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340 | else |
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341 | return 1; |
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342 | } |
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