| 133 | /// |
| 134 | template<class InputIterator> |
| 135 | inline bool prev_permutation(InputIterator first, |
| 136 | InputIterator last, |
| 137 | command_queue &queue = system::default_queue()) |
| 138 | { |
| 139 | typedef typename std::iterator_traits<InputIterator>::value_type value_type; |
| 140 | |
| 141 | if(first == last) return false; |
| 142 | |
| 143 | InputIterator first_element = |
| 144 | detail::prev_permutation_helper(first, last, queue); |
| 145 | |
| 146 | if(first_element == last) |
| 147 | { |
| 148 | reverse(first, last, queue); |
| 149 | return false; |
| 150 | } |
| 151 | |
| 152 | value_type first_value = first_element.read(queue); |
| 153 | |
| 154 | InputIterator ceiling_element = |
| 155 | detail::pp_floor(first_element + 1, last, first_value, queue); |
| 156 | |
| 157 | value_type ceiling_value = ceiling_element.read(queue); |
| 158 | |
| 159 | first_element.write(ceiling_value, queue); |
| 160 | ceiling_element.write(first_value, queue); |
| 161 | |
| 162 | reverse(first_element + 1, last, queue); |
| 163 | |
| 164 | return true; |
| 165 | } |
| 166 | |
| 167 | } // end compute namespace |
| 168 | } // end boost namespace |