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---
language: scala
filename: learn.scala
author: George Petrov
author_url: http://www.github.com/petrovg
---
Scala - the scalable language
```c
/*
Set yourself up:
1) Download Scala - http://www.scala-lang.org/downloads
2) unzip/untar in your favourite location and put the bin subdir on the path
3) Start a scala REPL by typing scala. You should see the prompt:
scala>
This is the so called REPL. You can run commands in the REPL. Let do just that:
*/
println(10) // prints the integer 10
println("Boo!") // printlns the string Boo!
// Evaluating a command gives you the type and value of the result
1 + 7
/* The above line results in:
scala> 1 + 7
res29: Int = 8
This means the result of evaluating 1 + 7 is an object of type Int with a value of 8
1+7 will give you the same result
*/
// Everything is an object, including a function type these in the repl:
7 // results in res30: Int = 7 (res30 is just a generated var name for the result)
// The next line gives you a function that takes an Int and returns it squared
(x:Int) => x * x
// You can assign this function to an identifier, like this:
val sq = (x:Int) => x * x
/* The above says this
sq: Int => Int = <function1>
Which means that this time we gave an explicit name to the value - sq is a function that take an Int and returns Int.
sq can be executed as follows:
*/
sq(10) // Gives you this: res33: Int = 100. The result is the Int with a value 100
// Data structures
val a = Array(1, 2, 3, 5, 8, 13)
a(0)
a(3)
a(21) // Throws an exception
val m = Map("fork" -> "tenedor", "spoon" -> "cuchara", "knife" -> "cuchillo")
m("fork")
m("spoon")
m("bottle") // Throws an exception
val safeM = m.withDefaultValue("no lo se")
safeM("bottle")
val s = Set(1, 3, 7)
s(0)
s(1)
/* Look up the documentation of map here - http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.Map
* and make sure you can read it
*/
// Tuples
// Combinators
s.map(sq)
val sSquared = s. map(sq)
sSquared.filter(_ < 10)
sSquared.reduce (_+_)
// For comprehensions
for { n <- s } yield sq(n)
val nSquared2 = for { n <- s } yield sq(n)
for { n <- nSquared2 if n < 10 } yield n
for { n <- s; nSquared = n * n if nSquared < 10} yield nSquared
// Conditionals
val x = 10
if (x == 1) println("yeah")
if (x == 10) println("yeah")
if (x == 11) println("yeah")
if (x == 11) println ("yeah") else println("nope")
println(if (x == 10) "yeah" else "nope")
val text = if (x == 10) "yeah" else "nope"
// Object oriented features
// Case classes
case class Person(name:String, phoneNumber:String)
Person("George", "1234") == Person("Kate", "1236")
// Pattern matching
val me = Person("George", "1234")
me match { case Person(name, number) => "We matched someone : " + name + ", phone : " + number }
me match { case Person(name, number) => "Match : " + name; case _ => "Hm..." }
me match { case Person("George", number) => "Match"; case _ => "Hm..." }
me match { case Person("Kate", number) => "Match"; case _ => "Hm..." }
me match { case Person("Kate", _) => "Girl"; case Person("George", _) => "Boy" }
val kate = Person("Kate", "1234")
kate match { case Person("Kate", _) => "Girl"; case Person("George", _) => "Boy" }
// Regular expressions
// TODO
// Strings
println("ABCDEF".length)
println("ABCDEF".substring(2, 6))
println("ABCDEF".replace("C", "3"))
val n = 45
println(s"We have $n apples")
val a = Array(11, 9, 6)
println(s"My second daughter is ${a(2-1)} years old")
// Input and output
```
## Further resources
[Scala for the impatient](http://horstmann.com/scala/)
[Twitter Scala school(http://twitter.github.io/scala_school/)
[The scala documentation]
Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user)
|
