diff options
| -rw-r--r-- | scala.html.markdown | 56 |
1 files changed, 54 insertions, 2 deletions
diff --git a/scala.html.markdown b/scala.html.markdown index a1396b4d..8bcbc27f 100644 --- a/scala.html.markdown +++ b/scala.html.markdown @@ -93,6 +93,7 @@ s(1) // Tuples + // Combinators s.map(sq) @@ -114,6 +115,37 @@ for { n <- nSquared2 if n < 10 } yield n for { n <- s; nSquared = n * n if nSquared < 10} yield nSquared +/* NB Those were not for loops. The semantics of a for loop is 'repeat', whereas a for-comprehension + defines a relationship between two sets of data. Research this further */ + + + +// Loops and iteration + +1 to 5 +val r = 1 to 5 +r.foreach( println ) + +r foreach println +// NB: Scala is quite lenien when it comes to dots and brackets - study the rules separately. This +// helps write DSLs and APIs that read like English + +(5 to 1 by -1) foreach ( println ) + +var i = 0 +while (i < 10) { println("i " + i); i+=1 } + +while (i < 10) { println("i " + i); i+=1 } // Yes, again. What happened? Why? + +i // Show the value of i. Note that while is a loop in the classical sense - it executes + // sequentially while changing the loop variable. while is very fast, faster that Java + // 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. +def showNumbersInRange(a:Int, b:Int):Unit = { print(a); if (a < b) showNumbersInRange(a+1, b) } + // Conditionals @@ -128,11 +160,13 @@ if (x == 11) println ("yeah") else println("nope") println(if (x == 10) "yeah" else "nope") val text = if (x == 10) "yeah" else "nope" - +var i = 0 +while (i < 10) { println("i " + i); i+=1 } // Object oriented features + // Case classes case class Person(name:String, phoneNumber:String) @@ -141,6 +175,7 @@ Person("George", "1234") == Person("Kate", "1236") + // Pattern matching val me = Person("George", "1234") @@ -163,7 +198,14 @@ kate match { case Person("Kate", _) => "Girl"; case Person("George", _) => "Boy" // Regular expressions -// TODO +val email = "(.*)@(.*)".r // The suffix .r invokes method r on String, which makes it a Regex + +val email(user, domain) = "henry@zkpr.com" + +"mrbean@pyahoo.com" match { + case email(name, domain) => "I know your name, " + name +} + // Strings @@ -178,6 +220,16 @@ println(s"We have $n apples") val a = Array(11, 9, 6) println(s"My second daughter is ${a(2-1)} years old") +// Some characters need to be 'escaped', e.g. a double quote inside a string: +val a = "They stood outside the \"Rose and Crown\"" + +// Triple double-quotes allow for strings to span multiple rows and contain funny characters +val html = """<form id="daform"> + <p>Press belo', Joe</p> + | <input type="submit"> + </form>""" + + // Input and output |