te')); return $arr; } /* 遍历用户所有主题 * @param $uid 用户ID * @param int $page 页数 * @param int $pagesize 每页记录条数 * @param bool $desc 排序方式 TRUE降序 FALSE升序 * @param string $key 返回的数组用那一列的值作为 key * @param array $col 查询哪些列 */ function thread_tid_find_by_uid($uid, $page = 1, $pagesize = 1000, $desc = TRUE, $key = 'tid', $col = array()) { if (empty($uid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('uid' => $uid), array('tid' => $orderby), $page, $pagesize, $key, $col); return $arr; } // 遍历栏目下tid 支持数组 $fid = array(1,2,3) function thread_tid_find_by_fid($fid, $page = 1, $pagesize = 1000, $desc = TRUE) { if (empty($fid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('fid' => $fid), array('tid' => $orderby), $page, $pagesize, 'tid', array('tid', 'verify_date')); return $arr; } function thread_tid_delete($tid) { if (empty($tid)) return FALSE; $r = thread_tid__delete(array('tid' => $tid)); return $r; } function thread_tid_count() { $n = thread_tid__count(); return $n; } // 统计用户主题数 大数量下严谨使用非主键统计 function thread_uid_count($uid) { $n = thread_tid__count(array('uid' => $uid)); return $n; } // 统计栏目主题数 大数量下严谨使用非主键统计 function thread_fid_count($fid) { $n = thread_tid__count(array('fid' => $fid)); return $n; } ?>c++ - random_shuffle error : inability to pass a minstd_rand generator - Stack Overflow

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    c++ - random_shuffle error : inability to pass a minstd_rand generator - Stack Overflow

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    Following the documentation provided here I am trying to randomly permute a std::vector like this:

    #include <vector>
#include <boost/random/linear_congruential.hpp>
#include <boost/range/algorithm.hpp>

int main(){
    std::vector<int> vecint;
    for(int i = 0; i < 10; i++)
        vecint.push_back(i);
    boost::minstd_rand gen(0);
    boost::range::random_shuffle(vecint, gen);
}

    This however does not compile. Godbolt link is here:

    I think that the following condition specified in the documentation does not hold:

    RandomAccessRange's distance type is convertible to Generator's argument type.

    How can I find out the distance type of std::vector and the particular generator's argument type to figure out if they are compatible or not?

    Following the documentation provided here I am trying to randomly permute a std::vector like this:

    #include <vector>
#include <boost/random/linear_congruential.hpp>
#include <boost/range/algorithm.hpp>

int main(){
    std::vector<int> vecint;
    for(int i = 0; i < 10; i++)
        vecint.push_back(i);
    boost::minstd_rand gen(0);
    boost::range::random_shuffle(vecint, gen);
}

    This however does not compile. Godbolt link is here: https://godbolt./z/zjhh6r3xd

    I think that the following condition specified in the documentation does not hold:

    RandomAccessRange's distance type is convertible to Generator's argument type.

    How can I find out the distance type of std::vector and the particular generator's argument type to figure out if they are compatible or not?

    • c++
    • boost
    • boost-random
    Share Improve this question asked Feb 17 at 11:29 One_Cable5781One_Cable5781 655 bronze badges 7
    • 2 Why boost? What is wrong with for example std::shuffle(vecint.begin(), vecint.end(), gen); – Öö Tiib Commented Feb 17 at 13:15
    • I want this to be compiler independent. Unfortunately, I have verified that gcc and MSVC have different implementations of std::shuffle – One_Cable5781 Commented Feb 17 at 13:17
    • 1 gcc and MSVC have the standart implementation for std::shuffle. – dalfaB Commented Feb 17 at 13:28
    • @dalfaB Please see this question I made over at /r/cpp_questions as to why the outcomes are different and not reproducible and repeateable across gcc and msvc: reddit/r/cpp_questions/comments/1iqi3cm/… – One_Cable5781 Commented Feb 17 at 13:30
    • Do you want the shuffling to produce the exact same ordering independent of host compiler and target system? Why? Why is it a problem that the container have different order of its element after shuffling, depending on compiler/platform? It's supposed to be random after all... – Some programmer dude Commented Feb 17 at 13:49
     |  Show 2 more comments

    1 Answer 1

    Reset to default 2

    That minstd_rand is not generator functor but engine. Something like that works:

    #include <iostream>
#include <vector>
#include <boost/random/linear_congruential.hpp>
#include <boost/random/uniform_int.hpp>
#include <boost/random/variate_generator.hpp>
#include <boost/range/algorithm.hpp>

int main() {
    std::vector<int> vecint;
    for(int i = 0; i < 10; i++)
        vecint.push_back(i);
    boost::minstd_rand engine(0);
    boost::uniform_int<> distribution;
    boost::variate_generator gen(engine, distribution);
    boost::range::random_shuffle(vecint, gen);
    boost::range::copy(vecint, std::ostream_iterator<int>(std::cout, " "));
    std::cout << std::endl;
}

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