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Returns an iterator pointing to the position before the first element in the container.
The iterator returned shall not be dereferenced: It is meant to be used as an argument for member functions emplace_after, insert_after, erase_after or splice_after, to specify the beginning of the sequence as the location where the action is performed.
If the forward_list object is const-qualified, the function returns a const_iterator. Otherwise, it returns an iterator.
Member types iterator and const_iterator are forward iterator types (pointing to an element and to a const element, respectively).
Output:
No contained elements are accessed by the call, but the iterator returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
The copy construction or assignment of the returned iterator is also guaranteed to never throw.
Reference
C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
-
<cfenv> (fenv.h)C++11
- <cfloat> (float.h)
-
<cinttypes> (inttypes.h)C++11
- <ciso646> (iso646.h)
- <climits> (limits.h)
- <clocale> (locale.h)
- <cmath> (math.h)
- <csetjmp> (setjmp.h)
- <csignal> (signal.h)
- <cstdarg> (stdarg.h)
-
<cstdbool> (stdbool.h)C++11
- <cstddef> (stddef.h)
-
<cstdint> (stdint.h)C++11
- <cstdio> (stdio.h)
- <cstdlib> (stdlib.h)
- <cstring> (string.h)
-
<ctgmath> (tgmath.h)C++11
- <ctime> (time.h)
-
<cuchar> (uchar.h)C++11
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
-
<array>C++11
- <deque>
-
<forward_list>C++11
- <list>
- <map>
- <queue>
- <set>
- <stack>
-
<unordered_map>C++11
-
<unordered_set>C++11
- <vector>
-
Input/Output:
Multi-threading:
-
<atomic>C++11
-
<condition_variable>C++11
-
<future>C++11
-
<mutex>C++11
-
<thread>C++11
-
Other:
- <algorithm>
- <bitset>
-
<chrono>C++11
-
<codecvt>C++11
- <complex>
- <exception>
- <functional>
-
<initializer_list>C++11
- <iterator>
- <limits>
- <locale>
- <memory>
- <new>
- <numeric>
-
<random>C++11
-
<ratio>C++11
-
<regex>C++11
- <stdexcept>
- <string>
-
<system_error>C++11
-
<tuple>C++11
-
<type_traits>C++11
-
<typeindex>C++11
- <typeinfo>
- <utility>
- <valarray>
<forward_list>
-
forward_listC++11
forward_list
-
forward_list::~forward_listC++11
-
forward_list::forward_listC++11
member functions
-
forward_list::assignC++11
-
forward_list::before_beginC++11
-
forward_list::beginC++11
-
forward_list::cbefore_beginC++11
-
forward_list::cbeginC++11
-
forward_list::cendC++11
-
forward_list::clearC++11
-
forward_list::emplace_afterC++11
-
forward_list::emplace_frontC++11
-
forward_list::emptyC++11
-
forward_list::endC++11
-
forward_list::erase_afterC++11
-
forward_list::frontC++11
-
forward_list::get_allocatorC++11
-
forward_list::insert_afterC++11
-
forward_list::max_sizeC++11
-
forward_list::mergeC++11
-
forward_list::operator=C++11
-
forward_list::pop_frontC++11
-
forward_list::push_frontC++11
-
forward_list::removeC++11
-
forward_list::remove_ifC++11
-
forward_list::resizeC++11
-
forward_list::reverseC++11
-
forward_list::sortC++11
-
forward_list::splice_afterC++11
-
forward_list::swapC++11
-
forward_list::uniqueC++11
-
non-member overloads
- Reference
- <forward_list>
- forward_list
- forward_list::before_begin
public member function
<forward_list>
std:: forward_list::before_begin
iterator before_begin() noexcept;const_iterator before_begin() const noexcept;
Return iterator to before beginning
The iterator returned shall not be dereferenced: It is meant to be used as an argument for member functions emplace_after, insert_after, erase_after or splice_after, to specify the beginning of the sequence as the location where the action is performed.
Parameters
noneReturn Value
An iterator to the position before the beginning of the sequence.If the forward_list object is const-qualified, the function returns a const_iterator. Otherwise, it returns an iterator.
Member types iterator and const_iterator are forward iterator types (pointing to an element and to a const element, respectively).
Example
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|
Output:
mylist contains: 11 20 30 40 50 |
Complexity
Constant.Iterator validity
No changes.Data races
The container is accessed (neither the const nor the non-const versions modify the container).No contained elements are accessed by the call, but the iterator returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
Exception safety
No-throw guarantee: this member function never throws exceptions.The copy construction or assignment of the returned iterator is also guaranteed to never throw.
See also
- forward_list::cbefore_begin
- Return const_iterator to before beginning (public member function)
- forward_list::begin
- Return iterator to beginning (public member type)
- forward_list::end
- Return iterator to end (public member function)
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Spotted an error? contact us