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      std::ranges::partition_copy,std::ranges::partition_copy_result

      From cppreference.com
      <cpp‎ |algorithm‎ |ranges
       
       
      Algorithm library
      Constrained algorithms and algorithms on ranges(C++20)
      Constrained algorithms, e.g.ranges::copy,ranges::sort, ...
      Execution policies(C++17)
      Sorting and related operations
      Partitioning operations
      Sorting operations
      Binary search operations
      (on partitioned ranges)
      Set operations (on sorted ranges)
      Merge operations (on sorted ranges)
      Heap operations
      Minimum/maximum operations
      (C++11)
      (C++17)
      Lexicographical comparison operations
      Permutation operations
      C library
      Numeric operations
      Operations on uninitialized memory
       
      Constrained algorithms
      All names in this menu belong to namespacestd::ranges
      Non-modifying sequence operations
      Modifying sequence operations
      Partitioning operations
      Sorting operations
      Binary search operations (on sorted ranges)
             
             
      Set operations (on sorted ranges)
      Heap operations
      Minimum/maximum operations
      Permutation operations
      Fold operations
      Operations on uninitialized storage
      Return types
       
      Defined in header<algorithm>
      Call signature
      template<std::input_iterator I,std::sentinel_for<I> S,

               std::weakly_incrementable O1,std::weakly_incrementable O2,
               class Proj=std::identity,
               std::indirect_unary_predicate<std::projected<I, Proj>> Pred>
      requiresstd::indirectly_copyable<I, O1>&&
               std::indirectly_copyable<I, O2>
      constexpr partition_copy_result<I, O1, O2>
          partition_copy( I first, S last, O1 out_true, O2 out_false,

                          Pred pred, Proj proj={});
      (1)(since C++20)
      template<ranges::input_range R,

               std::weakly_incrementable O1,std::weakly_incrementable O2,
               class Proj=std::identity,
               std::indirect_unary_predicate<std::projected<iterator_t<R>, Proj>> Pred>
      requiresstd::indirectly_copyable<ranges::iterator_t<R>, O1>&&
               std::indirectly_copyable<ranges::iterator_t<R>, O2>
      constexpr partition_copy_result<ranges::borrowed_iterator_t<R>, O1, O2>
          partition_copy( R&& r, O1 out_true, O2 out_false,

                          Pred pred, Proj proj={});
      (2)(since C++20)
      Helper types
      template<class I,class O1,class O2>
      using partition_copy_result=ranges::in_out_out_result<I, O1, O2>;
      (3)(since C++20)
      1) Copies the elements from the input range[firstlast) to two different output ranges depending on the value returned by the predicatepred. The elements that satisfy the predicatepred after projection byproj are copied to the range beginning atout_true. The rest of the elements are copied to the range beginning atout_false. The behavior is undefined if the input range overlaps either of the output ranges.
      2) Same as(1), but usesr as the source range, as if usingranges::begin(r) asfirst, andranges::end(r) aslast.

      The function-like entities described on this page arealgorithm function objects (informally known asniebloids), that is:

      Contents

      [edit]Parameters

      first, last - the iterator-sentinel pair defining the sourcerange of elements to copy from
      r - the source range of elements to copy from
      out_true - the beginning of the output range for the elements that satisfypred
      out_false - the beginning of the output range for the elements that do not satisfypred
      pred - predicate to apply to the projected elements
      proj - projection to apply to the elements

      [edit]Return value

      {last, o1, o2}, whereo1 ando2 are the ends of the output ranges respectively, after the copying is complete.

      [edit]Complexity

      Exactlyranges::distance(first, last) applications of the corresponding predicatecomp and any projectionproj.

      [edit]Possible implementation

      struct partition_copy_fn{template<std::input_iterator I,std::sentinel_for<I> S,std::weakly_incrementable O1,std::weakly_incrementable O2,class Proj=std::identity,std::indirect_unary_predicate<             std::projected<I, Proj>> Pred>    requiresstd::indirectly_copyable<I, O1>&&std::indirectly_copyable<I, O2>constexpr ranges::partition_copy_result<I, O1, O2>        operator()(I first, S last, O1 out_true, O2 out_false,                   Pred pred, Proj proj={})const{for(; first!= last;++first)if(!!std::invoke(pred,std::invoke(proj,*first)))*out_true=*first,++out_true;else*out_false=*first,++out_false;return{std::move(first), std::move(out_true), std::move(out_false)};} template<ranges::input_range R,std::weakly_incrementable O1,std::weakly_incrementable O2,class Proj=std::identity,std::indirect_unary_predicate<std::projected<iterator_t<R>, Proj>> Pred>    requiresstd::indirectly_copyable<ranges::iterator_t<R>, O1>&&std::indirectly_copyable<ranges::iterator_t<R>, O2>constexpr ranges::partition_copy_result<ranges::borrowed_iterator_t<R>, O1, O2>        operator()(R&& r, O1 out_true, O2 out_false, Pred pred, Proj proj={})const{return(*this)(ranges::begin(r),ranges::end(r), std::move(out_true),                       std::move(out_false), std::move(pred), std::move(proj));}}; inlineconstexpr partition_copy_fn partition_copy{};

      [edit]Example

      Run this code
      #include <algorithm>#include <cctype>#include <iostream>#include <iterator>#include <vector> int main(){constauto in={'N','3','U','M','1','B','4','E','1','5','R','9'}; std::vector<int> o1(size(in)), o2(size(in)); auto pred=[](char c){returnstd::isalpha(c);}; auto ret= std::ranges::partition_copy(in, o1.begin(), o2.begin(), pred); std::ostream_iterator<char> cout{std::cout," "};std::cout<<"in = ";    std::ranges::copy(in, cout);std::cout<<"\no1 = ";std::copy(o1.begin(), ret.out1, cout);std::cout<<"\no2 = ";std::copy(o2.begin(), ret.out2, cout);std::cout<<'\n';}

      Output:

      in = N 3 U M 1 B 4 E 1 5 R 9o1 = N U M B E Ro2 = 3 1 4 1 5 9

      [edit]See also

      divides a range of elements into two groups
      (algorithm function object)[edit]
      divides elements into two groups while preserving their relative order
      (algorithm function object)[edit]
      copies a range of elements to a new location
      (algorithm function object)[edit]
      copies a range of elements omitting those that satisfy specific criteria
      (algorithm function object)[edit]
      copies a range dividing the elements into two groups
      (function template)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/ranges/partition_copy&oldid=180532"

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