1 | #ifndef theplu_yat_utility_segment |
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2 | #define theplu_yat_utility_segment |
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3 | |
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4 | // $Id: Segment.h 2357 2010-12-01 21:08:29Z peter $ |
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5 | |
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6 | /* |
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7 | Copyright (C) 2010 Peter Johansson |
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8 | |
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9 | This file is part of the yat library, http://dev.thep.lu.se/yat |
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10 | |
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11 | The yat library is free software; you can redistribute it and/or |
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12 | modify it under the terms of the GNU General Public License as |
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13 | published by the Free Software Foundation; either version 3 of the |
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14 | License, or (at your option) any later version. |
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15 | |
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16 | The yat library is distributed in the hope that it will be useful, |
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17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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19 | General Public License for more details. |
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20 | |
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21 | You should have received a copy of the GNU General Public License |
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22 | along with yat. If not, see <http://www.gnu.org/licenses/>. |
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23 | */ |
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24 | |
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25 | #include "yat_assert.h" |
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26 | |
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27 | #include <algorithm> |
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28 | #include <functional> |
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29 | |
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30 | namespace theplu { |
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31 | namespace yat { |
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32 | namespace utility { |
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33 | |
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34 | /** |
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35 | \brief a class for a Segment or Interval |
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36 | |
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37 | A Segment is defined by its \a begin and \a end. The end is not |
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38 | included in the Segment, i.e., you could write the Segment as |
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39 | [begin, end). Type T must be comparable, optionally with a |
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40 | comparator Compare, which should implement <a |
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41 | href="http://www.sgi.com/tech/stl/StrictWeakOrdering.html"> |
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42 | Strict Weak Ordering.</a>. |
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43 | |
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44 | \since new in yat 0.7 |
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45 | */ |
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46 | template<typename T, class Compare = std::less<T> > |
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47 | class Segment |
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48 | { |
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49 | public: |
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50 | /** |
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51 | type the Segment holds |
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52 | */ |
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53 | typedef T value_type; |
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54 | |
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55 | /** |
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56 | \brief default constructor |
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57 | */ |
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58 | Segment(void) {} |
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59 | |
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60 | /** |
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61 | \brief Constructor |
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62 | |
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63 | Creates a segment [begin, end) |
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64 | */ |
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65 | Segment(const T& begin, const T& end) |
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66 | : begin_(begin), end_(end) {} |
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67 | |
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68 | /** |
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69 | \return reference to first element in Segment |
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70 | */ |
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71 | T& begin(void) { return begin_; } |
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72 | |
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73 | /** |
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74 | \return const reference to first element in Segment |
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75 | */ |
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76 | const T& begin(void) const { return begin_; } |
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77 | |
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78 | /** |
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79 | \return reference to first element greater than Segment |
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80 | */ |
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81 | T& end(void) { return end_; } |
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82 | |
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83 | /** |
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84 | \return const reference to first element greater than Segment |
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85 | */ |
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86 | const T& end(void) const { return end_; } |
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87 | |
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88 | private: |
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89 | T begin_; |
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90 | T end_; |
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91 | |
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92 | // using compiler generated copying |
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93 | //Segment(const Segment&); |
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94 | //Segment& operator=(const Segment&); |
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95 | }; |
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96 | |
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97 | /** |
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98 | This function takes two Segment and compare them with comparator |
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99 | Compare. If all elements in \a lhs is less than all elements in |
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100 | \a rhs, \c true is returned. In other words, \c false is returned |
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101 | if \a rhs.begin() is less than \a lhs.end(). |
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102 | |
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103 | The exception is if both \a lhs and \a rhs are empty Segment |
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104 | (i.e. begin equals end) and their begins and ends are equal, in |
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105 | which case \c false is returned. This exception implies that |
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106 | compare(x,x) always returns false. |
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107 | |
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108 | \relates Segment |
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109 | |
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110 | \since new in yat 0.7 |
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111 | */ |
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112 | template<typename T, class Compare> |
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113 | bool compare(const Segment<T, Compare>& lhs, const Segment<T, Compare>& rhs) |
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114 | { |
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115 | Compare c; |
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116 | // begin <= end |
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117 | YAT_ASSERT(!c(lhs.end(), lhs.begin())); |
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118 | YAT_ASSERT(!c(rhs.end(), rhs.begin())); |
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119 | // take care of case when both sides are zero segments |
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120 | if (!c(lhs.begin(), lhs.end()) && !c(rhs.begin(), rhs.end())) { |
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121 | return c(lhs.begin(), rhs.begin()); |
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122 | } |
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123 | |
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124 | return ! c(rhs.begin(), lhs.end()); |
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125 | } |
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126 | |
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127 | /** |
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128 | \return -1 if compare(lhs, rhs) is \c true, +1 if compare(rhs, |
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129 | lhs) is \c true, and 0 otherwise |
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130 | |
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131 | \relates Segment |
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132 | |
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133 | \see compare(const Segment<T, Compare>&, const Segment<T, Compare>&) |
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134 | |
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135 | \since new in yat 0.7 |
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136 | */ |
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137 | template<typename T, class Compare> |
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138 | int compare_3way(const Segment<T, Compare>& lhs, |
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139 | const Segment<T, Compare>& rhs) |
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140 | { |
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141 | if (compare(lhs, rhs)) |
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142 | return -1; |
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143 | if (compare(rhs, lhs)) |
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144 | return 1; |
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145 | return 0; |
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146 | } |
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147 | |
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148 | /** |
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149 | \return -1 if \a element is less than all elements in \a segment, |
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150 | 0 if \a element overlaps with \a segment, and 1 otherwise. |
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151 | |
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152 | \relates Segment |
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153 | |
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154 | \since new in yat 0.7 |
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155 | */ |
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156 | template<typename T, class Compare> |
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157 | int compare_3way(const T& element, |
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158 | const Segment<T, Compare>& segment) |
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159 | { |
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160 | Compare comp; |
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161 | if (comp(element, segment.begin())) |
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162 | return -1; |
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163 | if (comp(element, segment.end())) |
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164 | return 0; |
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165 | return 1; |
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166 | } |
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167 | |
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168 | /** |
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169 | \return intersection of \a a and \a b. If \a a and \a b do not |
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170 | overlap an empty Section is returned (begin==end), but the exact |
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171 | value of begin is undefined. |
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172 | |
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173 | \relates Segment |
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174 | |
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175 | \since new in yat 0.7 |
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176 | */ |
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177 | template<typename T, class Compare> |
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178 | Segment<T, Compare> intersection(const Segment<T, Compare>& a, |
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179 | const Segment<T, Compare>& b) |
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180 | { |
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181 | Compare comp; |
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182 | Segment<T, Compare> result; |
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183 | |
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184 | result.begin() = std::max(a.begin(), b.begin(), comp); |
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185 | // the first max is needed in case a and b don't overlap |
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186 | result.end() = std::max(result.begin(), |
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187 | std::min(a.end(), b.end(), comp), |
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188 | comp); |
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189 | return result; |
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190 | } |
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191 | |
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192 | }}} |
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193 | #endif |
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