Reverse iterators have a member base() which returns a corresponding forward iterator. Beware that this isn’t an iterator that refers to the same object – it actually refers to the next object in the sequence. This is so that rbegin() corresponds with end() and rend() corresponds with begin(). So if you want to return an … Read more
here it is, obtaining a reference to the coresponding pointer of an iterator use : example: string my_str= “hello world”; string::iterator it(my_str.begin()); char* pointer_inside_buffer=&(*it); //<– [notice operator * returns a reference so doing & on a reference will give you the address].
I think it is entirely legitimate – an Iterator is just a stream of “stuff”. Why should the stream necessarily be bounded? Plenty of other languages (e.g. Scala) have the concept of unbounded streams built in to them and these can be iterated over. For example, using scalaz scala> val fibs = (0, 1).iterate[Stream](t2 => … Read more
a.push_back(x) is defined to have identical semantics to (void)a.insert(a.end(),x) for sequence containers that support it. See table 68 in ISO/IEC 14882:2003 23.1.1/12 [lib.sequence.reqmts]. Regarding the running time of vector.push_back(x) vs. vector.insert(vector.end(), x) consider the emphasized part: Table 68 lists sequence operations that are provided for some types of sequential containers but not others. An implementation … Read more
You must be using Python 3. In Python 2, the objects zip and range did behave as you were suggesting, returning lists. They were changed to generator-like objects which produce the elements on demand rather than expand an entire list into memory. One advantage was greater efficiency in their typical use-cases (e.g. iterating over them). … Read more
You could also write something like this: <% if @messages.each do |message| %> <%# code or partial to display the message %> <% end.empty? %> You have no messages. <% end %>
Try the reversed builtin: for c in reversed(string): print c The reversed() call will make an iterator rather than copying the entire string. PEP 322 details the motivation for reversed() and its advantages over other approaches.
Yes. Map is a sorted container, the reverse iterator must return the elements in reverse (i.e. decreasing) order of their keys. [Edit: as Charles Bailey points out in his answer, your code gives the greatest key if it exists – i.e. if the map is non-empty]
Channels are useful, but closures are often more suitable. package main import “fmt” func main() { gen := newEven() fmt.Println(gen()) fmt.Println(gen()) fmt.Println(gen()) gen = nil // release for garbage collection } func newEven() func() int { n := 0 // closure captures variable n return func() int { n += 2 return n } } … Read more
The most readable way I’ve done this in the past is to use std::vector::erase combined with std::remove_if. In the example below, I use this combination to remove any number less than 10 from a vector. (For non-c++0x, you can just replace the lambda below with your own predicate:) // a list of ints int myInts[] … Read more