alvin alexander

flatmap

Scala List class: methods, examples, and syntax

By Alvin Alexander. Last updated: August 16 2018

This page contains a large collection of examples of how to use the methods on the Scala List class.

The Scala List class as an immutable, linear, linked-list class. It’s very efficient when it makes sense for your algorithms to (a) prepend all new elements, (b) work with it in terms of its head and tail elements, and (c) use functional methods that traverse the list from beginning to end, such as filter, map, foldLeft, reduceLeft.

Scala Seq class: methods, examples, and syntax

By Alvin Alexander. Last updated: August 16 2018

This page contains a large collection of examples of how to use the methods on the Scala Seq class.

Important note about Seq, IndexedSeq, and LinearSeq

As an important note, I use Seq in the following examples to keep things simple, but in your code you should be more precise and use IndexedSeq or LinearSeq where appropriate. As the Seq class Scaladoc states:

Scala: A look at flatMap and map on Option

By Alvin Alexander. Last updated: May 21 2018

As a quick Scala tip, if you haven’t worked with the flatMap on an Option much, it can help to know that flatMap’s function should return an Option, which you can see in this REPL example:

scala> Some(1).flatMap{ i => Option(i) }
res0: Option[Int] = Some(1)

You can tell this by looking at the function signature in the scaladoc for the flatMap method on the Option class:

Scala Vector transformer methods (syntax, examples)

By Alvin Alexander. Last updated: May 21 2018

This page contains a large collection of examples of how to use Scala Vector class transformer methods.

Transformer methods

A transformer method is a method that constructs a new collection from an existing collection.

Another Scala nested Option + flatMap example alvin January 20, 2018 - 3:09pm

After yesterday’s Scala nested Option + flatMap/for example, here’s another example of plowing through nested Options with flatMap. First, start with some nested options:

val o1 = Option(1)
val oo1 = Option(o1)
val ooo1 = Option(oo1)

Here are those same three lines, with the data type for each instance shown in the comments:

Scala: Examples of for-expressions being converted to map and flatMap

By Alvin Alexander. Last updated: May 21 2018

Without any explanation, here are a couple of source code examples from my book, Learning Functional Programming in Scala. The only thing I’ll say about this code is that I created it in the process of writing that book, and the examples show how the Scala compiler translates for-expressions into map and flatMap calls behind the scenes.

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