From cppreference.com
Defined in header
Call signature
template<classT,std::output_iterator<constT&>O,std::sentinel_for<O>S>constexprOfill(Ofirst,Slast,constT&value); (1)(since C++20)
(until C++26)template<classO,std::sentinel_for<O>S,classT=std::iter_value_t<O>>requiresstd::output_iterator<O,constT&>constexprOfill(Ofirst,Slast,constT&value);(since C++26)template<classT,ranges::output_range<constT&>R>constexprranges::borrowed_iterator_t<R>fill(R&&r,constT&value); (2)(since C++20)
(until C++26)template<classR,classT=ranges::range_value_t<R>>requiresranges::output_range<R,constT&>constexprranges::borrowed_iterator_t<R>fill(R&&r,constT&value);(since C++26)template</*execution-policy*/Ep,std::random_access_iteratorO,std::sized_sentinel_for<O>S,classT=std::iter_value_t<O>>requiresstd::indirectly_writable<O,constT&>Ofill(Ep&&policy,Ofirst,Slast,constT&value); (3) (since C++26)template</*execution-policy*/Ep,/*sized-random-access-range*/R,classT=ranges::range_value_t<R>>requiresstd::indirectly_writable<ranges::iterator_t<R>,constT&>ranges::borrowed_iterator_t<R>fill(Ep&&policy,R&&r,constT&value); (4) (since C++26)For the definition of /*execution-policy*/, see
; for the definition of /*sized-random-access-range*/, see
.
1,2) Assigns value to all elements in the target range [first, last) or r.
3,4) Same as (1,2), 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
first, last - the pair of iterators defining the target
r - the target range value - the value to be assigned policy - the
to use Return value
The past-the-end iterator of the source range.
Complexity
Given N as ranges::distance(first,last) or ranges::distance(r):
1-4) Exactly N assignments.
Exceptions
3,4) 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).
Possible implementation
structfill_fn{template<classO,std::sentinel_for<O>S,classT=std::iter_value_t<O>>requiresstd::output_iterator<O,constT&>constexprOoperator()(Ofirst,Slast,constT&value)const{while(first!=last)*first++=value;returnfirst;}template<classR,classT=ranges::range_value_t<R>>requiresranges::output_range<R,constT&>constexprranges::borrowed_iterator_t<R>operator()(R&&r,constT&value)const{return(*this)(ranges::begin(r),ranges::end(r),value);}template<ranges::forward_rangeR,classT=ranges::range_value_t<R>>requiresranges::output_range<R,constT&>constexprranges::borrowed_iterator_t<R>operator()(R&&r,constT&value)const{return(*this)(ranges::begin(r),ranges::next(ranges::begin(r),ranges::end(r)),value);}};inlineconstexprfill_fnfill;Notes
macroValueStdFeature
__cpp_lib_algorithm_default_value_type
(C++26)
for algorithms (
)Example
Run this code
#include<algorithm>#include<complex>#include<iostream>#include<vector>voidprintln(constauto&seq){for(constauto&e:seq)std::cout<<e<<' ';std::cout<<'\n';}intmain(){std::vector<int>v{0,1,2,3,4,5};// set all elements to -1 using overload (1)std::ranges::fill(v.begin(),v.end(),-1);println(v);// set all element to 10 using overload (2)std::ranges::fill(v,10);println(v);std::vector<std::complex<double>>nums{{1,3},{2,2},{4,8}};println(nums);#ifdef __cpp_lib_algorithm_default_value_typestd::ranges::fill(nums,{4,2});// T gets deduced#elsestd::ranges::fill(nums,std::complex<double>{4,2});#endifprintln(nums);}Output:
-1 -1 -1 -1 -1 -1 10 10 10 10 10 10 (1,3) (2,2) (4,8) (4,2) (4,2) (4,2) See also
copy-assigns the given value to every element in a range
(function template)
(C++20)
assigns a value to a number of elements
(algorithm function object)
(C++20)(C++20)
copies a range of elements to a new location
(algorithm function object)
(C++20)
saves the result of a function in a range
(algorithm function object)
(C++20)
applies a function to a range of elements
(algorithm function object)
(C++26)
fills a range with random numbers from a uniform random bit generator
(algorithm function object)