home search about rss feed twitter ko-fi

The Scala REPL (Video)

Lesson Notes

Introduction: Based on Chapter 8 of Learn Scala 3 The Fast Way! (Book 1: The Adventure Begins)

  • REPL acronym (read/evaluate/print/loop)

How to start

It’s currently April, 2023, and this will change at some point:

$ scala-cli repl
  • I start the REPL with a classpath

    • clear function
    • help function

Create variables and expressions

  • val is the keyword to create an immutable variable
  • types: Int, String, Char, Boolean, Double
  • res0, res1, etc.

Scala is both an FP and OOP language

  • type -1
    • instance of Int type
    • .[tab]
    • has all these methods
  • type "foo".tab
    • has 254 methods
    • type .to then tab (tab completion)

Create and use functions

def double(i: Int): Int = i * 2
val a = 1
val res = double(a)

REPL commands

  • :reset
  • :help
  • Quitting

    • :quit
    • ^d

Show Scastie as an online REPL

Ammonite repl

  • double function output is different
  • -1.tab output is different
$ scala-cli --power repl --amm

Summary

  • Showed how to start REPL
  • How to create variables
  • res0, etc. (creates own variables)
  • Tab completion
  • :quit, ctrl-d

Update: All of my new videos are now on
LearnScala.dev