std:: begin (std::valarray)

The overload of std::begin for valarray returns an iterator of unspecified type referring to the first element in the numeric array.

The iterator returned from this function is invalidated when the member function resize() is called on v or when the lifetime of v ends, whichever comes first.

Parameters

Return value

Iterator to the first value in the numeric array.

Exceptions

May throw implementation-defined exceptions.

Notes

Unlike other functions that take std::valarray arguments, begin() cannot accept the replacement types (such as the types produced by expression templates) that may be returned from expressions involving valarrays: std:: begin ( v1 + v2 ) is not portable, std:: begin ( std:: valarray < T > ( v1 + v2 ) ) has to be used instead.

The intent of this function is to allow range for loops to work with valarrays, not to provide container semantics.

Example

#include <algorithm>
#include <iostream>
#include <valarray>
 
void show(const std::valarray<int>& v)
{
    std::for_each(std::begin(v), std::end(v), [](int c)
    {
        std::cout << c << ' ';
    });
    std::cout << '\n';
};
 
int main()
{
    const std::valarray<int> x{47, 70, 37, 52, 90, 23, 17, 33, 22, 16, 21, 4};
    const std::valarray<int> y{25, 31, 71, 56, 21, 21, 15, 34, 21, 27, 12, 6};
 
    show(x); 
    show(y); 
 
    const std::valarray<int> z{x + y};
 
    for (char c : z)
        std::cout << c;
}

47 70 37 52 90 23 17 33 22 16 21 4 
25 31 71 56 21 21 15 34 21 27 12 6 
Hello, C++!

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also