SCALA FOREACH HOW TO

Next, call the par method on your collection to turn it into a parallel collection, and repeat the experiment: No matter how many times you print it, you’ll always see that same result that’s the linear world you’re used to. Next, print the sequence, and you’ll see that it prints as usual:Īs expected, that example prints the string 0123456789. To demonstrate this, first create a sequential collection, such as a Vector: You can convert an existing collection to a parallel collection. In either case, test your algorithm to make sure you see the benefit you’re expecting. When creating a collection, use one of the Scala’s parallel collection classes, or convert an existing collection to a parallel collection. You want to improve the performance of an algorithm by using Scala’s parallel collections.

SCALA FOREACH HOW TO

This is Recipe 13.12, “Examples of how to use parallel collections in Scala.” Problem This is an excerpt from the Scala Cookbook. show more info on classes/objects in repl.See Recipe 10.10, “ How to loop over a Scala collection with a ‘for’ loop”, for more information. Scala’s for loop provides another powerful way to iterate over the elements in a collection.See Recipe 11.18, “ How to traverse a Scala Map (Map class)”, for other ways to iterate over a map.However, I generally prefer the following approach:Ĭase(movie, rating) => println(s'key: $movie, value: $rating') 'Hello world it's Al'.split(' ').foreach')) To declare a multiline function, use this format: If your algorithm is used only once, you don’t have to declare it as a method or function just pass it to foreach as a function literal: In the following example, the printIt method takes a Char, does something with it, and returns nothing:īecause a String is a sequence of type Char, printIt can be called in a foreach method on a String as follows: DiscussionĪs long as your function (or method) takes one parameter of the same type as the elements in the collection and returns nothing ( Unit), it can be called from a foreach method. In a situation like this, where a function literal consists of one statement that takes a single argument, it can be condensed to this form:įor a simple case like this, the syntax in the last example is typically used. You can further shorten this expression by using the ubiquitous underscore wildcard character instead of using a temporary variable:

For most expressions, Scala can infer the type, so specifying i: Int isn’t necessary: That’s the longhand way of writing that code. Because it doesn’t return anything, it’s said that it’s used for its “side effect.”Īs an example, a common use of foreach is to output information: Side Effects: The foreach method applies your function to each element of the collection, but it doesn’t return a value. As foreach executes, it passes one element at a time from the collection to your function until it reaches the last element in the collection.

The input parameter type should match the type stored in the collection. The function you define should take an element as an input parameter, and should not return anything. The foreach method on Scala collections classes takes a function as an argument.

You want to iterate over the elements in a Scala collection class with the foreach method. This is Recipe 10.9, “How to loop over a Collection with foreach”. This is an excerpt from the Scala Cookbook(partially modified for the internet).