From cppreference.com
Defined in header
template<classForwardIt,classT>voidfill(ForwardItfirst,ForwardItlast,constT&value); (1)(constexpr since C++20)
(until C++26)template<classForwardIt,classT=typenamestd::iterator_traits<ForwardIt>::value_type>constexprvoidfill(ForwardItfirst,ForwardItlast,constT&value);(since C++26)template<classExecutionPolicy,classForwardIt,classT>voidfill(ExecutionPolicy&&policy,ForwardItfirst,ForwardItlast,constT&value); (2)(since C++17)
(until C++26)template<classExecutionPolicy,classForwardIt,classT=typenamestd::iterator_traits<ForwardIt>::value_type>voidfill(ExecutionPolicy&&policy,ForwardItfirst,ForwardItlast,constT&value);(since C++26)1) Assigns value to all elements in the target range [first, last).
2) Same as (1), but executed according to policy.
This overload participates in overload resolution only if the value of the following expression is true:
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(until C++20)std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(since C++20)If value is not
to first, the program is ill-formed.
Parameters
first, last - the pair of iterators defining the target
value - the value to be assigned policy - the
to use Type requirements -ForwardIt must meet the requirements of
. Complexity
Exactly std::distance(first,last) assignments.
Exceptions
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).
Possible implementation
template<classForwardIt,classT=typenamestd::iterator_traits<ForwardIt>::value_type>voidfill(ForwardItfirst,ForwardItlast,constT&value){for(;first!=last;++first)*first=value;}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{0,1,2,3,4,5,6,7,8};println(v);// set all of the elements to 8std::fill(v.begin(),v.end(),8);println(v);std::vector<std::complex<double>>nums{{1,3},{2,2},{4,8}};println(nums);#ifdef __cpp_lib_algorithm_default_value_typestd::fill(nums.begin(),nums.end(),{4,2});#elsestd::fill(nums.begin(),nums.end(),std::complex<double>{4,2});#endifprintln(nums);}Output:
0 1 2 3 4 5 6 7 8 8 8 8 8 8 8 8 8 8 (1,3) (2,2) (4,8) (4,2) (4,2) (4,2) Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 T was required to be
, but
T is not always writable to ForwardItrequired to be writable instead See also
(C++20)
assigns a range of elements a certain value
(algorithm function object)
copy-assigns the given value to N elements in a range
(function template & algorithm function object)
(C++20)
(C++11)
copies a range of elements to a new location
(function template & algorithm function object)
(C++20)(C++20)
assigns the results of successive function calls to every element in a range
(function template & algorithm function object)
(C++20)
applies a function to a range of elements, storing results in a destination range
(function template & algorithm function object)
(C++20)