Calls to itertools.imap() in Python 2 or map() in Python 3 can be replaced by equivalent generator expressions: sum(1 for dummy in it) This also uses a lazy generator, so it avoids materializing a full list of all iterator elements in memory.
Came across this question while investigating for a similar problem. Even if the question is old, now in the time of C++ 11 and boost 1.54 it is pretty easy to do using the Boost.Range library. It features a join-function, which can join two ranges into a single one. Here you might incur performance penalties, … Read more
If Iterator is a random access iterator, then std::iterator_traits<Iterator>::iterator_category will be std::random_access_iterator_tag. The cleanest way to implement this is probably to create a second function template and have Foo call it: template <typename Iterator> void FooImpl(Iterator first, Iterator last, std::random_access_iterator_tag) { // … } template <typename Iterator> void Foo(Iterator first, Iterator last) { typedef typename … Read more
Your suspicion is correct: the iterator has been consumed. In actuality, your iterator is a generator, which is an object which has the ability to be iterated through only once. type((i for i in range(5))) # says it’s type generator def another_generator(): yield 1 # the yield expression makes it a generator, not a function … Read more
The standard doesn’t quite spell it out, but v.erase(q) is defined, “Erases the element pointed to by q” in [sequence.reqmts]. This means that q must actually point to an element, which the end iterator doesn’t. Passing in the end iterator is undefined behavior. Unfortunately, you need to write: auto it = std::find(…); if (it != … Read more
In list<tNode<T>*>::iterator, you have a dependant name, that is, a name that depends on a template parameter. As such, the compiler can’t inspect list<tNode<T>*> (it doesn’t have its definition at this point) and so it doesn’t know whether list<tNode<T>*>::iterator is either a static field or a type. In such a situation, the compiler assumes that … Read more
Had the same need so wrote a little class for it. Here are some examples: Generator<Integer> simpleGenerator = new Generator<Integer>() { public void run() throws InterruptedException { yield(1); // Some logic here… yield(2); } }; for (Integer element : simpleGenerator) System.out.println(element); // Prints “1”, then “2”. Infinite generators are also possible: Generator<Integer> infiniteGenerator = new … Read more
What you want is lazy iteration over an object or array. This is not possible in ES5 (thus not possible in node.js). We will get this eventually. The only solution is finding a node module that extends V8 to implement iterators (and probably generators). I couldn’t find any implementation. You can look at the spidermonkey … Read more
It’s quite simple. Say I have a vector: std::vector<int> vec; I fill it with some data. Then I want to get some iterators to it. Maybe pass them around. Maybe to std::for_each: std::for_each(vec.begin(), vec.end(), SomeFunctor()); In C++03, SomeFunctor was free to be able to modify the parameter it gets. Sure, SomeFunctor could take its parameter … Read more
I think that you are better off not trying to do the .seek(0) but rather opening the file from the filename each time. And I don’t recommend you just return self in the __iter__() method. That means you only ever have one instance of your object. I don’t know how likely it is for someone … Read more