diff options
| -rw-r--r-- | scala.html.markdown | 139 |
1 files changed, 134 insertions, 5 deletions
diff --git a/scala.html.markdown b/scala.html.markdown index 8bcb5975..8e00f135 100644 --- a/scala.html.markdown +++ b/scala.html.markdown @@ -2,6 +2,7 @@ language: Scala contributors: - ["George Petrov", "http://github.com/petrovg"] + - ["Dominic Bou-Samra, "http://dbousamra.github.com"] filename: learn.scala --- @@ -28,7 +29,43 @@ println(10) // prints the integer 10 println("Boo!") // printlns the string Boo! -// Evaluating a command gives you the type and value of the result +// Some basics + +// Printing, and forcing a new line on the next print +println("Hello world!") +// Printing, without forcing a new line on next print +print("Hello world") + +// Declaring values is done using either var or val +// val declarations are immutable, whereas var's are mutable. Immutablility is a good thing. +val x = 10 // x is now 10 +x = 20 // error: reassignment to val +var x = 10 +x = 20 // x is now 20 + +// Single line comments start with two forward slashes +/* +Multi line comments look like this. +*/ + +// Boolean values +true +false + +// Boolean operations +!true // false +!false // true +true == false // false +10 > 5 // true + +// Math is as per usual +1 + 1 // 2 +2 - 1 // 1 +5 * 3 // 15 +6 / 2 // 3 + + +// Evaluating a command in the REPL gives you the type and value of the result 1 + 7 @@ -64,6 +101,20 @@ val sq = (x:Int) => x * x sq(10) // Gives you this: res33: Int = 100. The result is the Int with a value 100 +// Scala allows methods and functions to return, or take as parameters, other functions or methods. + +val add10: Int => Int = _ + 10 // A function taking an Int and returning an Int +List(1, 2, 3) map add10 // List(11, 12, 13) - add10 is applied to each element + +// Anonymous functions can be used instead of named functions: +List(1, 2, 3) map (x => x + 10) + +// And the underscore symbol, can be used if there is just one argument to the anonymous function. It gets bound as the variable +List(1, 2, 3) map (_ + 10) + +TODO // If the anonymous block AND the function you are applying both take one argument, you can even omit the underscore +List("Dom", "Bob", "Natalia") foreach println + // Data structures @@ -124,6 +175,20 @@ sSquared.filter(_ < 10) sSquared.reduce (_+_) +// The filter function takes a predicate (a function from A -> Boolean) and selects all elements which satisfy the predicate +List(1, 2, 3) filter (_ > 2) // List(3) +List( + Person(name = "Dom", age = 23), + Person(name = "Bob", age = 30) +).filter(_.age > 25) // List(Person("Bob", 30)) + + +// Scala a foreach method defined on certain collections that takes a type returning Unit (a void method) +aListOfNumbers foreach (x => println(x)) +aListOfNumbers foreach println + + + // For comprehensions @@ -152,6 +217,7 @@ r foreach println (5 to 1 by -1) foreach ( println ) +// A while loops var i = 0 while (i < 10) { println("i " + i); i+=1 } @@ -162,8 +228,14 @@ i // Show the value of i. Note that while is a loop in the classical sense - // loops, but using the combinators and comprehensions above is easier to understand // and parallelize -// Tail recursion is an idiomatic way of doing things in Scala. Recursive functions need an -// explicit return type, the compile can't infer it. Here it's Unit. +// A do while loop +do { + println("x is still less then 10"); + x += 1 +} while (x < 10) + +// Tail recursion is an idiomatic way of doing recurring things in Scala. Recursive functions need an +// explicit return type, the compiler can't infer it. Here it's Unit. def showNumbersInRange(a:Int, b:Int):Unit = { print(a); if (a < b) showNumbersInRange(a+1, b) } @@ -175,7 +247,7 @@ 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") +if (x == 11) println ("yeah") else println("nay") println(if (x == 10) "yeah" else "nope") val text = if (x == 10) "yeah" else "nope" @@ -183,8 +255,21 @@ val text = if (x == 10) "yeah" else "nope" var i = 0 while (i < 10) { println("i " + i); i+=1 } + + // Object oriented features +// Classname is Dog +class Dog { + //A method called bark, returning a String + def bark: String = { + // the body of the method + "Woof, woof!" + } +} + +// Classes can contain nearly any other construct, including other classes, functions, methods, objects, case classes, traits etc. + // Case classes @@ -230,6 +315,12 @@ val email(user, domain) = "henry@zkpr.com" // Strings +"Scala strings are surrounded by double quotes" // +'a' // A Scala Char +'Single quote strings don't exist' // Error +"Strings have the usual Java methods defined on them".length +"They also have some extra Scala methods.".reverse // See scala.collection.immutable.StringOps + println("ABCDEF".length) println("ABCDEF".substring(2, 6)) println("ABCDEF".replace("C", "3")) @@ -250,8 +341,45 @@ val html = """<form id="daform"> </form>""" + +// Application structure and organization + +// Importing things +import scala.collection.immutable.List + +// Import all "sub packages" +import scala.collection.immutable._ + +// Import multiple classes in one statement +import scala.collection.immutable.{List, Map} + +// Rename an import using '=>' +import scala.collection.immutable{ List => ImmutableList } + +// Import all classes, except some. The following excludes Map and Set: +import scala.collection.immutable.{Map => _, Set => _, _} + +// Your programs entry point is defined in an scala file using an object, with a single method, main: +object Application { + def main(args: Array[String]): Unit = { + // stuff goes here. + } +} + +// Files can contain multiple classes and objects. Compile with scalac + + + + // Input and output +// To read a file line by line +import scala.io.Source +for(line <- Source.fromPath("myfile.txt").getLines()) + println(line) + +// To write a file use Java's PrintWriter + ``` @@ -263,4 +391,5 @@ val html = """<form id="daform"> [The scala documentation] -Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user)
\ No newline at end of file +Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user) + |