Szathmáry László honlapja @ DEIK | Scala / variables, basic types, rich types

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Variables

scala> val x = 5 * 6 + 8 // val: constant, cannot change it later
x: Int = 38
scala> x = 2
<console>:8: error: reassignment to val
x = 2
^
scala> var y = 7 // var: a variable whose content can change
y: Int = 7
scala> y += 1
scala> y
res2: Int = 8
scala>

In Scala you are encouraged to use vals instead of vars.

If you want, you can specify the type too:

scala> val z: String = "hello" // z is a String
z: String = hello

scala> val width, height = 100 // sets both to 100
width: Int = 100
height: Int = 100

Basic types and rich types

scala> val z: String = "hello" // z is a String
z: String = hello

scala> :type z // type of a variable
String

scala> :type 6 + 5 // type of an expression
Int

Scala has seven numeric types, which are actually classes. Each class has a richer version, which includes lots of convenience methods.

normal	rich
Byte	RichByte
Char	RichChar
Short	RichShort
Int	RichInt
Long	RichLong
Float	RichFloat
Double	RichDouble
Boolean	RichBoolean

Example: when you write "1 to 10", it is a shorthand for "1.to(10)", i.e. an integer has a method called "to". How? This feature is added in the RichInt class.

String

The convenience methods of String are located in StringOps. Scala uses the String class of Java and adds lots of goodies to it in StringOps.