I'm interested in the implementation of the reverse iterator with rbegin(), rend() and operator++ of the class string, I can't find it in google, how can I do it? thanks in advance for any help or any link
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3 Answers
You could look in the implementation header files. (e.g. /usr/include/c++/4.1.2/string on Linux). This will typically just pull in a load of other headers where the real meat lies, such as bits/basic_string.h.
I don't know where they reside for e.g. VC++, but you can usually just get Intellisense to find it by creating a std::string, selecting it and pressing F12.
answered Oct 4, 2010 at 11:40
Oliver Charlesworth
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1 Comment
alxx
For VC++, it's something like C:\Program Files\Microsoft Visual Studio 9.0\VC\include (just search for header name).
There is a basic implementation of reverse_iterator in the STL.
It is templatized by the Iterator to be reverted.
The idea is quite simple, if you look at a range:
[first, second, .... last]
^ ^
begin end
rend rbegin
There is extra-work done, compared to a pure reverse iterator using this implementation, since for each dereference, you need to copy the iterator you hold, decrement it, and then dereference it.
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Reverse iteration for bidirectional iterators is implemented in the std::reverse_iterator template.
The implementation of reverse iterators for std::string doesn't take more than:
template <xxx>
class basic_string
{
public:
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
typedef std::reverse_iterator<iterator> reverse_iterator;
reverse_iterator rbegin() { return reverse_iterator(this->end()); }
const_reverse_iterator rbegin() const { return const_reverse_iterator(this->end()); }
reverse_iterator rend() { return reverse_iterator(this->begin()); }
const_reverse_iterator rend() const { return const_reverse_iterator(this->begin()); }
//...
};
(Copied from GCC's implementation.)
