NAME¶

std::begin(std::valarray) - std::begin(std::valarray)

Synopsis¶

template< class T > (1) (since C++11)
/*unspecified1*/ begin( valarray<T>& v );
template< class T > (2) (since C++11)
/*unspecified2*/ begin( const valarray<T>& v );

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

1) The return type meets the requirements of mutable LegacyRandomAccessIterator.
2) The return type meets the requirements of constant LegacyRandomAccessIterator.

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

Parameters¶

v - a numeric array

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¶

// Run this code

#include <iostream>
#include <valarray>
#include <algorithm>

auto show = [](std::valarray<int> const& 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 };

std::for_each(std::begin(z), std::end(z), [](char c) { std::cout << c; });
}

Output:¶

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++!

See also¶

std::end(std::valarray) specializes std::end
(C++11) (function template)