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std::experimental::sample(3)  C++ Standard Libary std::experimental::sample(3)

NAME
       std::experimental::sample - std::experimental::sample

Synopsis
	  Defined in header <experimental/algorithm>
	  template< class PopulationIterator, class
	  SampleIterator,

	  class	Distance, class	URBG >
	  SampleIterator  sample(  PopulationIterator first,	  (1) (library
       fundamentals TS)
	  PopulationIterator last,
	  SampleIterator out, Distance n,

	  URBG&& g);
	  template< class PopulationIterator, class
	  SampleIterator, class	Distance >
								    (library
       fundamentals TS
	  SampleIterator sample( PopulationIterator first,	(2) v2)
	  PopulationIterator last,

	  SampleIterator out, Distance n);

	  Selects n elements from the sequence [first; last)  such  that  each
       possible	sample
	  has  equal probability of appearance,	and writes those selected ele-
       ments into the
	  output iterator out

	  If n is greater than the number of elements in the sequence, selects
       last-first
	  elements.

	  The algorithm	is stable only if  PopulationIterator  meets  the  re-
       quirements of
	  LegacyForwardIterator

	  1) Random numbers are	generated using	the random number generator g.
	  2) Random numbers are	generated using	the per-thread engine.

Parameters
	  first,  last	      -	      pair of iterators	forming	the range from
       which to	make
				     the sampling (the population)
	  out		     -	     the output	iterator where the samples are
       written.	Must
				     not be in the [first;last)	range
	  n		     -	     number of samples to make
	  g		     -	     the random	number generator used  as  the
       source of
				     randomness
	  -
	  PopulationIterator  must  meet the requirements of LegacyInputItera-
       tor.
	  -
	  SampleIterator must meet the requirements of LegacyOutputIterator.
	  -
	  SampleIterator must also meet	the requirements of LegacyRandomAcces-
       sIterator if
	  PopulationIterator doesn't meet LegacyForwardIterator
	  -
	  PopulationIterator's value type must be writeable to out
	  -
	  Distance must	be an integer type
	  -
	  URBG must meet the requirements of UniformRandomBitGenerator and its
       return type
	  must be convertible to Distance

Return value
	  Returns a copy of out	after the last sample that  was	 output,  that
       is, end of the
	  sample range.

Complexity
	  Linear in std::distance(first,last)

Notes
	  This	function  may  implement  selection sampling or	reservoir sam-
       pling.

Example
       // Run this code

	#include <iostream>
	#include <random>
	#include <string>
	#include <iterator>
	#include <experimental/algorithm>

	int main()
	{
	    std::string	in = "abcdefgh", out;
	    std::experimental::sample(in.begin(),   in.end(),	 std::back_in-
       serter(out),
				      5,	  std::mt19937{std::random_de-
       vice{}()});
	    std::cout << "five random letters out of " << in <<	" : "  <<  out
       << '\n';
	}

Possible output:
	five random letters out	of abcdefgh : cdefg

See also
	  random_shuffle
	  shuffle	 randomly re-orders elements in	a range
	  (until C++17)	 (function template)
	  (C++11)

http://cppreference.com		  2022.07.31	  std::experimental::sample(3)

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