The most substantive difference between the for loop and the forEach method is that, with the former, you may break out of the loop. You can simulate continue by simply returning from the function passed to forEach, but there is no way to stop looping altogether. Aside from that, the two accomplish effectively the same … Read more
I have the same problem. I usually resort to String#split: “ABCDEFG”.split(“”).each do |i| puts i end I guess you could also implement it yourself like this: class String def each_char self.split(“”).each { |i| yield i } end end Edit: yet another alternative is String#each_byte, available in Ruby 1.8.6, which returns the ASCII value of each … Read more
Use a list instead of a generator when: 1) You need to access the data multiple times (i.e. cache the results instead of recomputing them): for i in outer: # used once, okay to be a generator or return a list for j in inner: # used multiple times, reusing a list is better … … Read more
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.
The for loop listens for StopIteration explicitly. The purpose of the for statement is to loop over the sequence provided by an iterator and the exception is used to signal that the iterator is now done; for doesn’t catch other exceptions raised by the object being iterated over, just that one. That’s because StopIteration is … Read more
They are iterable, but they are not iterators. They can be passed to iter() to get an iterator for them either implicitly (e.g. via for) or explicitly, but they are not iterators in and of themselves.
Yes you can, it just take some massaging 😉 The trick is to use composition: instead of iterating over the container directly, you “zip” it with an index along the way. Specialized zipper code: template <typename T> struct iterator_extractor { typedef typename T::iterator type; }; template <typename T> struct iterator_extractor<T const> { typedef typename T::const_iterator … Read more
RecursiveIteratorIterator is a concrete Iterator implementing tree traversal. It enables a programmer to traverse a container object that implements the RecursiveIterator interface, see Iterator in Wikipedia for the general principles, types, semantics and patterns of iterators. In difference to IteratorIterator which is a concrete Iterator implementing object traversal in linear order (and by default accepting … Read more
Use the old for loop as: for (auto it = values.begin(); it != values.end(); ++it ) { auto & value = *it; //… } With this, you’ve value as well as iterator it. Use whatever you want to use. EDIT: Although I wouldn’t recommended this, but if you want to use range-based for loop (yeah, … Read more
Yes. Do the following: Collection<string> myCollection = new Collection<string>; foreach (string curString in myCollection.Skip(3)) //Dostuff Skip is an IEnumerable function that skips however many you specify starting at the current index. On the other hand, if you wanted to use only the first three you would use .Take: foreach (string curString in myCollection.Take(3)) These can … Read more