Scala expressions and definitions cheatsheet

Intro

This is a cheatsheet of Scala expressions and definitions from Coursera online course Functional Programming Principles in Scala

What is Expression

Expression is any bit of Scala code that yields a result. In other words expression evaluates to a result or results in a value

Categories of expressions

• An identifier such as x, isValid
• A literal, like 0, 2, abc
• A function application, like sqrt(x)
• An operator application, like -x, x+y
• A selection, like math.abs
• A conditional expression, like if(x < 0) -x else z
• A block, like { val x = math.abs(y); x * 2}
• An anonymous function, like x => x + 1

What is definition

Definition of something is a giving it a name and implementation.

Definition types

• classes
• traits
• singleton objects
• fields
• methods
• local functions
• local variables
• etc

Abstract members can not be defined because definition always involve some kind of implementation.

Definition may or may not contain parameters. Parameters can be:

• call by value parameter, like (x: Int)
• call by name parameter, like (y: => Boolean)

Useful links

• Scala glossary from book “Programming in Scala”