From cppreference.com
Defined in header
Call signature
template<std::input_iteratorI,/*nothrow-forward-iterator*/O,/*nothrow-sentinel-for*/<O>S>requiresstd::constructible_from<std::iter_value_t<O>,std::iter_rvalue_reference_t<I>>uninitialized_move_n_result<I,O>uninitialized_move_n(Iifirst,std::iter_difference_t<I>count,Oofirst,Solast); (1)(since C++20)
(constexpr since C++26)template</*execution-policy*/Ep,std::random_access_iteratorI,/*nothrow-random-access-iterator*/O,/*nothrow-sized-sentinel-for*/<O>S>requiresstd::constructible_from<std::iter_value_t<O>,std::iter_rvalue_reference_t<I>>uninitialized_move_n_result<I,O>uninitialized_move_n(Ep&&policy,Iifirst,std::iter_difference_t<I>count,Oofirst,Solast); (2) (since C++26)Helper types
template<classI,classO>usinguninitialized_move_n_result=ranges::in_out_result<I,O>; (3) (since C++20)For the definition of /*execution-policy*/, see
; for the definition of other exposition-only concepts, see
.
1) Constructs elements in the destination range [ofirst, olast) from elements in the source range ifirst + [0, count) as if by
autoret=ranges::uninitialized_move(std::counted_iterator(std::move(ifirst),count),
std::default_sentinel,ofirst,olast);
return{std::move(ret.in).base(),ret.out};
If an exception is thrown during the initialization then the objects that already constructed in [ofirst, olast) are destroyed in an unspecified order. Also, the objects in the input range beginning at ifirst, that were already moved, are left in a valid but unspecified state.
If [ofirst, olast) overlaps with ifirst + [0, count), the behavior is undefined.
2) Same as (1), but executed according to policy.
The function-like entities described on this page are
(informally known as niebloids), that is:
Explicit template argument lists cannot be specified when calling any of them.
None of them are visible to
.
When any of them are found by
as the name to the left of the function-call operator,
is inhibited.
Parameters
ifirst - the beginning of the input range of elements to move from ofirst, olast - the iterator-sentinel pair defining the output
of elements to initialize count - the number of elements to move policy - the
to use Return value
As described above.
Exceptions
Any exception thrown on construction of the elements in the destination range.
2) During the execution process:
If the temporary memory resources required for parallelization are not available,
is thrown.
If an uncaught exception is thrown while accessing objects via an algorithm argument, the behavior is determined by the execution policy (for
,
is invoked).
Notes
An implementation may improve the efficiency of the ranges::uninitialized_move_n (by using e.g.
) if the value type of the output range is
.
macro ValueStdFeature
(C++26)Parallel range algorithms
__cpp_lib_raw_memory_algorithms
(C++26)constexpr for
specialized <memory> algorithms
, (
)Possible implementation
structuninitialized_move_n_fn{template<std::input_iteratorI,/*nothrow-forward-iterator*/O,/*nothrow-sentinel-for*/<O>S>requiresstd::constructible_from<std::iter_value_t<O>,std::iter_rvalue_reference_t<I>>constexprranges::uninitialized_move_n_result<I,O>operator()(Iifirst,std::iter_difference_t<I>count,Oofirst,Solast)const{autoiter=std::counted_iterator(std::move(ifirst),count);autoret=ranges::uninitialized_move(iter,std::default_sentinel,ofirst,olast);return{std::move(ret.in).base(),ret.out};}};inlineconstexpruninitialized_move_n_fnuninitialized_move_n{};Example
Run this code
#include<cstdlib>#include<iomanip>#include<iostream>#include<memory>#include<string>voidprint(autorem,autofirst,autolast){for(std::cout<<rem;first!=last;++first)std::cout<<std::quoted(*first)<<' ';std::cout<<'\n';}intmain(){std::stringin[]{"No","Diagnostic","Required",};print("initially, in: ",std::begin(in),std::end(in));if(constexprautosz=std::size(in);void*out=std::aligned_alloc(alignof(std::string),sizeof(std::string)*sz)){try{autofirst{static_cast<std::string*>(out)};autolast{first+sz};std::ranges::uninitialized_move_n(std::begin(in),sz,first,last);print("after move, in: ",std::begin(in),std::end(in));print("after move, out: ",first,last);std::ranges::destroy(first,last);}catch(...){std::cout<<"Exception!\n";}std::free(out);}}Possible output:
initially, in: "No" "Diagnostic" "Required" after move, in: "" "" "" after move, out: "No" "Diagnostic" "Required" See also