learnxinyminutes-docs/scala.html.markdown

language	author	author_url
scala	George Petrov	http://www.georgepetrov.com

/* 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 =

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)

// 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