std::iota
From cppreference.com
| Defined in header <numeric>
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| template< class ForwardIterator, class T > void iota( ForwardIterator first, ForwardIterator last, T value ); |
(since C++11) | |
Fills the range [first, last) with sequentially increasing values, starting with value and repetitively evaluating ++value.
Equivalent operation:
*(d_first) = value; *(d_first+1) = ++value; *(d_first+2) = ++value; *(d_first+3) = ++value; ...
Parameters
| first, last | - | the range of elements to fill with sequentially increasing values starting with value |
| value | - | initial value to store, the expression ++value must be well-formed |
Return value
(none)
Complexity
Exactly last - first increments and assignments.
Possible implementation
template<class ForwardIterator, class T> void iota(ForwardIterator first, ForwardIterator last, T value) { while(first != last) { *first++ = value; ++value; } } |
Notes
The function is named after the integer function ⍳ from the programming language APL. It was one of the STL components that were not included in C++98, but eventually made it into the standard library in C++11.
Example
The following example applies std::shuffle to a vector of std::list iterators since std::shuffle cannot be applied to a std::list directly. std::iota is used to populate both containers.
Run this code
#include <algorithm> #include <iostream> #include <list> #include <numeric> #include <random> #include <vector> int main() { std::list<int> l(10); std::iota(l.begin(), l.end(), -4); std::vector<std::list<int>::iterator> v(l.size()); std::iota(v.begin(), v.end(), l.begin()); std::shuffle(v.begin(), v.end(), std::mt19937{std::random_device{}()}); std::cout << "Contents of the list: "; for(auto n: l) std::cout << n << ' '; std::cout << '\n'; std::cout << "Contents of the list, shuffled: "; for(auto i: v) std::cout << *i << ' '; std::cout << '\n'; }
Possible output:
Contents of the list: -4 -3 -2 -1 0 1 2 3 4 5 Contents of the list, shuffled: 0 -1 3 4 -4 1 -2 -3 2 5
See also
| copy-assigns the given value to every element in a range (function template) | |
| assigns the results of successive function calls to every element in a range (function template) |