Hi! I wrote a Combination which is against to std::permutation. It can enumerate all result of a combination, such as selecting 3 chars from "ABCDE", by `dictionary order'. It's just like the std::permutation. The code is published at http://www.bxmy.org/code/combination.cpp. And I wrote a article about this Combination Algorithm in Chinese, http://www.bxmy.org/article/combination.pdf. Also, the code can be found in the enclosure. The combination has at least three functions: combination_adjust: should be called for initialize the sequence; next_combination: get next combination, like next_permutation; prev_combination: get previous combination, like prev_permutation. This algorithm separates all elements into two parts. One is [first, middle), the elements selected in. Other is [middle, last), the elements selected out. The steps are: 1) find the first element `Pout' in [first, middle) which should be selected out. 2) find the first element `Qin' in [middle, last) which should be selected in. 3) iter_swap(Pout, Qin). 4) merge [Pout+1, middle) and [Qin+1, last). It's simple and compatible with std::permutation well. I hope that it can be add into the STL. They are couple. Thanks. Ben T. Bear