What features of Module are defined as append and prepend? As specified in the text you quoted: the constants, methods, and module variables How they differ functionally? Both add methods of the mixed-in module to the passed module (class). The difference is in the lookup order of these methods, in case that the target class … Read more
I think the easiest would be to write: var list = listOf(2,3) println(list) // [2, 3] list = listOf(1) + list println(list) // [1, 2, 3] There is no specific tail implementation, but you can call .drop(1) to get the same. You can make this head\tail more generic by writing these extension properties: val <T> … Read more
You can assign to a slice: a[:0] = b Demo: >>> a = [1,2,3] >>> b = [4,5,6] >>> a[:0] = b >>> a [4, 5, 6, 1, 2, 3] Essentially, list.extend() is an assignment to the list[len(list):] slice. You can ‘insert’ another list at any position, just address the empty slice at that location: … Read more
Store a reference to the first message before you prepend new messages, and after you prepend, set the scroll to the offset of that message: $(document).on(‘scroll’, function() { var scroll = $(document).scrollTop(); if (scroll < 1) { // Store eference to first message var firstMsg = $(‘.message:first’); // Prepend new message here (I’m just cloning…) … Read more
The best way to determine the difference between both methods is to look it the source code. The source of ::: def ::[B >: A] (x: B): List[B] = new scala.collection.immutable.::(x, this) The source of +:: override def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[List[A], B, That]): That = bf match { case _: List.GenericCanBuildFrom[_] … Read more
Vectors are not designed for prepending. You have only O(n) prepend: user=> (into [:foo] [:bar :baz]) [:foo :bar :baz] What you want is most likely a finger tree.
Use a slice composite literal: []int{1}, For example: package main import ( “fmt” ) func main() { var x []int for i := 2; i < 10; i += 2 { x = append(x, i) } fmt.Println(x) x = append([]int{1}, x…) fmt.Println(x) } Playground: https://play.golang.org/p/Yc87gO7gJlD Output: [2 4 6 8] [1 2 4 6 8] … Read more
You can use selection.insert(newElement[, anotherExistingElement]) For example: selection.insert(“div”,”:first-child”) The above code will insert a div before the first child of selected element. Check documentation to learn more. Another possible way of inserting elements before any node (including plain texts): var parentEl = d3.select(“div”).node(); parentEl.insertBefore(document.createElement(“div”), parentEl.childNodes[0]); <script src=”https://d3js.org/d3.v3.min.js”></script> <div> This is a plain text <a></a> </div>
There actually is a similar function to the non-existing std::string::push_front, see the below example. Documentation of std::string::insert #include <iostream> #include <string> int main (int argc, char *argv[]) { std::string s1 (” world”); std::string s2 (“ello”); s1.insert (0, s2); // insert the contents of s2 at offset 0 in s1 s1.insert (0, 1, ‘h’); // insert … Read more
Python makes a lot of things easy and contains libraries and wrappers for a lot of common operations, but the goal is not to hide fundamental truths. The fundamental truth you are encountering here is that you generally can’t prepend data to an existing flat structure without rewriting the entire structure. This is true regardless … Read more