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Defined in header
Defined in header
Defined in header
(since C++23)
Defined in header
(since C++23)
Defined in header
Defined in header
(since C++26)
Defined in header
(since C++26)
Defined in header
Defined in header
Defined in header
Defined in header
(since C++26)
Defined in header
Defined in header
Defined in header
(since C++20)
Defined in header
(since C++23)
Defined in header
Defined in header
(since C++17)
Defined in header
Defined in header
Defined in header
Defined in header
template<classC>autobegin(C&c)->decltype(c.begin()); (1)(since C++11)
(constexpr since C++17)template<classC>autobegin(constC&c)->decltype(c.begin()); (2)(since C++11)
(constexpr since C++17)template<classT,std::size_tN>T*begin(T(&array)[N]); (3)(since C++11)
(noexcept since C++14)
(constexpr since C++14)template<classC>constexprautocbegin(constC&c)noexcept(/* see below */)->decltype(std::begin(c)); (4) (since C++14)Returns an iterator to the beginning of the given range.
1,2) Returns c.begin(), which is typically an iterator to the beginning of the sequence represented by c.
1) If C is a standard
, returns a C::iterator object.
2) If C is a standard
, returns a C::const_iterator object.
3) Returns a pointer to the beginning of array.
4) Returns std::begin(c), with c always treated as const-qualified.
If C is a standard
, returns a C::const_iterator object.
Parameters
c - a container or view with a begin member function array - an array of arbitrary type Return value
1,2)c.begin()
3)array
4)c.begin()
Exceptions
4)
specification:
noexcept(noexcept(std::begin(c)))Overloads
Custom overloads of begin may be provided for classes and enumerations that do not expose a suitable begin() member function, yet can be iterated. The following overloads are already provided by the standard library:
Similar to the use of swap (described in
), typical use of the begin function in generic context is an equivalent of usingstd::begin;begin(arg);, which allows both the
-selected overloads for user-defined types and the standard library function templates to appear in the same overload set.
template<typenameContainer,typenameFunction>voidfor_each(Container&&cont,Functionf){usingstd::begin;autoit=begin(cont);usingstd::end;autoend_it=end(cont);while(it!=end_it){f(*it);++it;}}Notes
The non-array overloads exactly reflect the behavior of C::begin. Their effects may be surprising if the member function does not have a reasonable implementation.
std::cbegin is introduced for unification of member and non-member range accesses. See also
.
If C is a shallow-const view, std::cbegin may return a mutable iterator. Such behavior is unexpected for some users. See also
and
.
Example
Run this code
#include<iostream>#include<iterator>#include<vector>intmain(){std::vector<int>v={3,1,4};autovi=std::begin(v);std::cout<<std::showpos<<*vi<<'\n';inta[]={-5,10,15};autoai=std::begin(a);std::cout<<*ai<<'\n';}Output:
+3 -5 See also
(C++11)(C++14)
returns an iterator to the end of a container or array
(function template)
(C++20)
returns an iterator to the beginning of a range
(customization point object)
(C++20)
returns an iterator to the beginning of a read-only range
(customization point object)