iterable - w3toppers.com

Check if a variable type is iterable?

You may create a trait for that: namespace detail { // To allow ADL with custom begin/end using std::begin; using std::end; template <typename T> auto is_iterable_impl(int) -> decltype ( begin(std::declval<T&>()) != end(std::declval<T&>()), // begin/end and operator != void(), // Handle evil operator , ++std::declval<decltype(begin(std::declval<T&>()))&>(), // operator ++ void(*begin(std::declval<T&>())), // operator* std::true_type{}); template <typename T> std::false_type … Read more

Using Objects in For Of Loops

The for..of loop only supports iterable objects like arrays, not objects. To iterate over the values of an object, use: for (var key in test) { var item = test[key]; }

Length of generator output [duplicate]

The easiest way is probably just sum(1 for _ in gen) where gen is your generator.

Kotlin’s Iterable and Sequence look exactly same. Why are two types required?

The key difference lies in the semantics and the implementation of the stdlib extension functions for Iterable<T> and Sequence<T>. For Sequence<T>, the extension functions perform lazily where possible, similarly to Java Streams intermediate operations. For example, Sequence<T>.map { … } returns another Sequence<R> and does not actually process the items until a terminal operation like … Read more

What is the difference between iterator and iterable and how to use them?

An Iterable is a simple representation of a series of elements that can be iterated over. It does not have any iteration state such as a “current element”. Instead, it has one method that produces an Iterator. An Iterator is the object with iteration state. It lets you check if it has more elements using … Read more

Why does Stream not implement Iterable?

People have already asked the same on the mailing list ☺. The main reason is Iterable also has a re-iterable semantic, while Stream is not. I think the main reason is that Iterable implies reusability, whereas Stream is something that can only be used once — more like an Iterator. If Stream extended Iterable then … Read more

How does a Python for loop with iterable work?

feed.entry is property of feed and it’s value is (if it’s not, this code will fail) object implementing iteration protocol (array, for example) and has iter method, which returns iterator object Iterator has next() method, returning next element or raising exception, so python for loop is actually: iterator = feed.entry.__iter__() while True: try: party = … Read more

What’s the shortest way to count the number of items in a generator/iterator?

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.

Why is Java’s Iterator not an Iterable?

An iterator is stateful. The idea is that if you call Iterable.iterator() twice you’ll get independent iterators – for most iterables, anyway. That clearly wouldn’t be the case in your scenario. For example, I can usually write: public void iterateOver(Iterable<String> strings) { for (String x : strings) { System.out.println(x); } for (String x : strings) … Read more