On Thu, Dec 17, 2009 at 6:44 PM, Steven D'Aprano <st...@remove-this-cybersource.com.au> wrote: > On Thu, 17 Dec 2009 12:07:59 -0800, Brendan Miller wrote: > >> I was thinking it would be cool to make python more usable in >> programming competitions by giving it its own port of the STL's >> algorithm library, which needs something along the lines of C++'s more >> powerful iterators. > > For the benefit of those of us who aren't C++ programmers, what do its > iterators do that Python's don't?
Python iterators basically only have one operation: next(), which returns the next element or throws StopIteration. In C++ terminology this is a Input iterator. It is good for writing "for each" loops or map reduce operations. An input iterator can't mutate the data it points to. C++ also has progressively stronger iterators: http://www.sgi.com/tech/stl/Iterators.html InputIterator <- read only, one direction, single pass ForwardIterator <- read/write, one direction, multi pass BidirectionalIterator <- read/write, can move in either direction RandomAccessIterator <- read/write, can move in either direction by an arbitrary amount in constant time (as powerful as a pointer) Each only adds extra operations over the one before. So a RandomAccessIterator can be used anywhere a InputIterator can, but not vice versa. Also, this is a duck typing relationship, not a formal class inheritance. Anything that quacks like a RandomAccessIterator is a RandomAccessIterator, but there is no actual RandomAccessIterator class. So, for instance stl sort function takes pair of random access iterator delimiting a range, and can sort any datastructure that can provide that powerful of an iterator (arrays, vectors, deques). http://www.sgi.com/tech/stl/sort.html MyCollection stuff; // put some stuff in stuff sort(stuff.begin(), stuff.end()); Where begin() and end() by convention return iterators pointing to the beginning and end of the sequence. -- http://mail.python.org/mailman/listinfo/python-list
