std::span<T,Extent>::begin, std::span<T,Extent>::cbegin

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

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forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Iterator invalidation

Member function table

Non-member function table

 

std::span

Member functions

span::span (C++20)

span::operator= (C++20)

Element access

span::front (C++20)

span::back (C++20)

span::operator[] (C++20)

span::data (C++20)

Iterators

span::beginspan::cbegin (C++20)(C++23)

span::endspan::cend (C++20)(C++23)

span::rbeginspan::crbegin (C++20)(C++23)

span::rendspan::crend (C++20)(C++23)

Observers

span::empty (C++20)

span::size (C++20)

span::size_bytes (C++20)

Subviews

span::first (C++20)

span::last (C++20)

span::subspan (C++20)

Non-member functions

as_bytesas_writable_bytes (C++20)(C++20)

Non-member constant

dynamic_extent (C++20)

Deduction guides(C++20)

 

constexpr iterator begin() const noexcept;	(1)	(since C++20)
constexpr const_iterator cbegin() const noexcept;	(3)	(since C++23)

Returns an iterator to the first element of the span.

If the span is empty, the returned iterator will be equal to end().

Parameters

(none)

Return value

Iterator to the first element.

Complexity

Constant.

Example

Run this code

#include <iostream>
#include <span>
 
void print(std::span<const int> array)
{
    std::cout << "array = ";
    for (auto it = array.begin(); it != array.end(); ++it)
        std::cout << *it << ' ';
    std::cout << '\n';
}
 
void set_first_element(std::span<int> sp, int new_value)
{
    if (not sp.empty())
    {
        std::cout << "old *begin = " << *sp.begin() << '\n';
        *sp.begin() = new_value;
        std::cout << "new *begin = " << *sp.begin() << '\n';
    }
}
 
int main()
{
    int array[]{1, 3, 4, 5};
    print(array);
    set_first_element(array, 2);
    print(array);
}

Output:

array = 1 3 4 5
old *begin = 1
new *begin = 2
array = 2 3 4 5

See also

end cend (C++20)(C++23)	returns an iterator to the end (public member function)
begincbegin (C++11)(C++14)	returns an iterator to the beginning of a container or array (function template)