public member function
<forward_list>
const_iterator cbefore_begin() const noexcept;
Return const_iterator to before beginning
Returns a const_iterator pointing to the position before the first element in the container.
A const_iterator is an iterator that points to const content. This iterator can be increased and decreased (unless it is itself also const), just like the iterator returned by forward_list::before_begin, but it cannot be used to modify the contents it points to.
The value returned shall not be dereferenced.
Return Value
A const_iterator to the position before the beginning of the sequence.
Member type const_iterator is a forward iterator type that points to a const element.
Example
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// forward_list::cbefore_begin
#include <iostream>
#include <forward_list>
int main ()
{
std::forward_list<int> mylist = {77, 2, 16};
mylist.insert_after ( mylist.cbefore_begin(), 19 );
std::cout << "mylist contains:";
for ( int& x: mylist ) std::cout << ' ' << x;
std::cout << '\n';
return 0;
}
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Output:
mylist contains: 19 77 2 16
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Iterator validity
No changes.
Data races
The container is accessed.
No contained elements are accessed by the call, but the iterator returned can be used to access them. 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.