Small steps to Scala (1/20) - the basics

Scala
1/20

This is the first blog in the series Small steps to Scala which are notes and code snippets gathered from projects, books, googling around or learning from the great people I've been working with.

With the assumption that you have the Scala interpreter installed and a Linux machine, we will start with the basics.

The basics

  • Scala interpreter
  • val & var
  • common types
  • operators & functions

Scala interpreter

Once you install Scala, run scala in your shell and you should see something similar to:

Welcome to Scala 2.11.8 (OpenJDK 64-Bit Server VM, Java 1.8.0_111).
Type in expressions for evaluation. Or try :help.

scala> 

This is the Scala REPL (Read, Evaluate, Print, Loop) which will take your input and behind the scenes will compile it into bytecode and execute it.

scala> 12 + 3 / 5
res0: Int = 12
scala> "String " + res0
res1: String = String 12

As one can see in the example above, there is no need to specify the type of the variable. Scala will do its best to infer the type and return the proper result type.

val & var variables

Variables are declared with var, while constants are declared with val.

scala> var name="George"
name: String = George
scala> name = "Scala"
name: String = Scala

The contents of the variable can be changed, however the type must be preserved, otherwise type mismatch error will be thrown.

This cannot be done with constants declared with val. An attempt to do so will result in a reassignment to val error.

scala> val t = 5
t: Int = 5
scala> t = 4
<console>:12: error: reassignment to val
       t = 4
         ^

Common types

These are some of the most common types used in Scala.

Data Type Description
Byte 8 bit signed value. Range from -128 to 127
Short 16 bit signed value. Range -32768 to 32767
Int 32 bit signed value. Range -2147483648 to 2147483647
Long 64 bit signed value. -9223372036854775808 to 9223372036854775807
Float 32 bit IEEE 754 single-precision float
Double 64 bit IEEE 754 double-precision float
Char 16 bit unsigned Unicode character. Range from U+0000 to U+FFFF
String A sequence of Chars
Boolean Either the literal true or the literal false
Unit Corresponds to no value
Null null or empty reference
Nothing The subtype of every other type; includes no values
Any The supertype of any type; any object is of type Any
AnyRef The supertype of any reference type

Operators & functions

Arithmetic operators + - * / % are methods.
Bit operators & | ^ >> << are also methods.

Here is a full list of operators in Scala.

  • a + b is the same with a.+(b)
  • 1 to 10 is the same with 1.to(10)
  • a method b is the same with a.method(b)
scala> 2 + 3 == 2.+(3)
res2: Boolean = true

scala> var a = 2
a: Int = 2
scala> a+=1
scala> a
res4: Int = 3


[+] Useful links
  • Download Scala
  • Install Scala
  • Getting Started
  • ScalaDoc
  • Scala tutorials
  • Cheat Sheet
  • Learn scala

  • Disclaimer: This is by no means an original work it is merely meant to serve as a compilation of thoughts, code snippets and teachings from different sources.