How to merge (concatenate) Lists in Scala

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 11.5, “How to Merge (Concatenate) Lists in Scala”


You want to merge/concatenate the contents of two lists.


Merge two lists using the ++, concat, or ::: methods. Given these two lists:

How to merge Scala sequential collections (List, Vector, ArrayBuffer, Array, Seq)

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 10.22, “How to Merge Scala Sequential Collections”


You want to join two sequences into one sequence, either keeping all of the original elements, finding the elements that are common to both collections, or finding the difference between the two sequences.


There are a variety of solutions to this problem, depending on your needs:

How to merge Scala Lists

Scala List FAQ: How do I merge a List in Scala?

NOTE: I wrote the solutions shown below a long time ago, and they are not optimal. I'll update this article when I have more time. The best approach is to prepend one List to the beginning of another List with the :: method.

There are at least three ways to merge/concatenate Scala List instances, as shown in the examples below.

How to concatenate strings in Perl

A Perl FAQ is "How do you concatenate (merge) two or more strings in Perl?"

Use the "." operator

The short answer is that you use the . operator. Here's a simple example:

$name = "alvin" . " " . "alexander";

Of course I could have also done that like this:

$name = "alvin " . "alexander";

but I wanted to show an example with more than two strings.

AppleScript string tip: How to concatenate strings

AppleScript string FAQ: How do I concatenate (merge) strings in AppleScript?

Fortunately string concatenation in AppleScript is pretty easy (if not a little different). To concatenate strings in AppleScript just use the ampersand (&) operator.

Here are a few AppleScript string concatenation examples, with a dialog thrown in so you can see the result: