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std::iota(3)		      C++ Standard Libary		  std::iota(3)

NAME
       std::iota - std::iota

Synopsis
	  Defined in header <numeric>
	  template<  class  ForwardIt,	class  T  >			(since
       C++11)
	  void iota( ForwardIt first, ForwardIt	last, T	value  );   (constexpr
       since C++20)

	  Fills	 the  range [first, last) with sequentially increasing values,
       starting	with
	  value	and repetitively evaluating ++value.

	  Equivalent  operation	 (assuming  ++value  returns  the  incremented
       value):

	*first	 = value;
	*++first = ++value;
	*++first = ++value;
	*++first = ++value;
	// repeats until last is reached

	  If any of the	following conditions is	satisfied, the program is ill-
       formed:

	    * T	is not convertible to the value	type of	ForwardIt.
	    *  The  expression ++val is	ill-formed, where val is a variable of
       type T.

Parameters
	  first, last -	the range of elements to fill  with  sequentially  in-
       creasing	values
			starting with value
	  value	      -	initial	value to store

Complexity
	  Exactly std::distance(first, last) increments	and assignments.

Possible implementation
	  template<class ForwardIt, class T>
	  constexpr // since C++20
	  void iota(ForwardIt first, ForwardIt last, T value)
	  {
	      for (; first != last; ++first, ++value)
		  *first = value;
	  }

Notes
	  The  function	is named after the integer function  from the program-
       ming language
	  APL. It was one of the STL components	 that  were  not  included  in
       C++98, but made it
	  into the standard library in C++11.

Example
	  The	following   example   applies  std::shuffle  to	 a  vector  of
       std::lists' iterators.
	  std::iota is used to populate	containers.

       // Run this code

	#include <algorithm>
	#include <iomanip>
	#include <iostream>
	#include <list>
	#include <numeric>
	#include <random>
	#include <vector>

	class BigData // inefficient to	copy
	{
	    int	data[1024]; /* some raw	data */
	public:
	    explicit BigData(int i = 0)	{ data[0] = i; /* ... */ }
	    operator int() const { return data[0]; }
	    BigData& operator=(int i) {	data[0]	= i; return *this; }
	    /* ... */
	};

	int main()
	{
	    std::list<BigData> l(10);
	    std::iota(l.begin(), l.end(), -4);

	    std::vector<std::list<BigData>::iterator> v(l.size());
	    std::iota(v.begin(), v.end(), l.begin());
	    // Vector of iterators (to original	data) is used to avoid	expen-
       sive copying,
	    //	and  because  std::shuffle  (below)  cannot  be	 applied  to a
       std::list directly.

	    std::shuffle(v.begin(),   v.end(),	  std::mt19937{std::random_de-
       vice{}()});

	    std::cout << "Original contents of the list	l:\t";
	    for	(const auto& n : l)
		std::cout << std::setw(2) << n << ' ';
	    std::cout << '\n';

	    std::cout << "Contents of l, viewed	via shuffled v:\t";
	    for	(const auto i :	v)
		std::cout << std::setw(2) << *i	<< ' ';
	    std::cout << '\n';
	}

Possible output:
	Original contents of the list l:	-4 -3 -2 -1  0	1  2  3	 4  5
	Contents of l, viewed via shuffled v:	-1  5 -4  0  2	1  4 -2	 3 -3

See also
	  ranges::iota_view  a	view consisting	of a sequence generated	by re-
       peatedly
	  views::iota	    incrementing an initial value
	  (C++20)	    (class template) (customization point object)
	  fill		    copy-assigns the given value to every element in a
       range
			    (function template)
	  ranges::fill	    assigns a range of elements	a certain value
	  (C++20)	    (niebloid)
			    assigns the	results	of successive  function	 calls
       to every	element
	  generate	    in a range
			    (function template)
	  ranges::generate  saves the result of	a function in a	range
	  (C++20)	    (niebloid)
	  ranges::iota	     fills  a  range with successive increments	of the
       starting	value
	  (C++23)	    (niebloid)

http://cppreference.com		  2024.06.10			  std::iota(3)

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