Some types of collections can add cheaply to the front (lists, seqs), while others can add cheaply to the back (vectors, queues, kinda-sorta lazy-seqs). Rather than using concat, if possible you should arrange to be working with one of those types (vector is most common) and just conj to it: (conj [1 2 3] 4) … Read more
With using only one reduce() you can do this. you don’t need map(). better approach is this: const values = [1,2,3,4]; const newValues= values.reduce((acc, cur) => { return acc.concat([cur*cur , cur*cur*cur, cur+1]); // or acc.push([cur*cur , cur*cur*cur, cur+1]); return acc; }, []); console.log(‘newValues=”, newValues) EDIT: The better approach is just using a flatMap (as @ori-drori … Read more
A linked list is like a conga line. Everyone holds the hips of the person in front of them and their hips are held in turn by the person to their rear, excepting only those in the front and the back. The only way to add people to the line is to find the right … Read more
You can iterate over c.most_common() to get the items in the desired order. See also the documentation of Counter.most_common(). Example: >>> c = collections.Counter(a=1, b=999) >>> c.most_common() [(‘b’, 999), (‘a’, 1)]
it’s easy to do in Kotlin: // v— the variable type can be removed var nameMap: MutableList<String> = persons.map { it.name }.toMutableList(); IF you want an immutable List, it can simplify as below: // v— the variable type can be removed var nameMap: List<String> = persons.map { it.name }; OR using function reference expression instead: … Read more
You can use $lookup ( multiple ) to get the records from multiple collections: Example: If you have more collections ( I have 3 collections for demo here, you can have more than 3 ). and I want to get the data from 3 collections in single object: The collection are as: db.doc1.find().pretty(); { “_id” … Read more
One difference is that conj accepts any number of arguments to insert into a collection, while cons takes just one: (conj ‘(1 2 3) 4 5 6) ; => (6 5 4 1 2 3) (cons 4 5 6 ‘(1 2 3)) ; => IllegalArgumentException due to wrong arity Another difference is in the class … Read more
Use of clone() in Java is tricky and questionable1,2. Effectively, clone() is a copy constructor and for that, the Dart List, Map and Set types each have a named constructor named .from() that perform a shallow copy; e.g. given these declarations Map<String, int> numMoons, moreMoons; numMoons = const <String,int>{ ‘Mars’ : 2, ‘Jupiter’ : 27 … Read more
IEnumerable<T> represents a series of items that you can iterate over (using foreach, for example), whereas IList<T> is a collection that you can add to or remove from. Typically you’ll want to be able to modify an Order by adding or removing OrderLines to it, so you probably want Order.Lines to be an IList<OrderLine>. Having … Read more
Length() tends to refer to contiguous elements – a string has a length for example. Count() tends to refer to the number of elements in a looser collection. Size() tends to refer to the size of the collection, often this can be different from the length in cases like vectors (or strings), there may be … Read more