During 2013 spring semester I will deliver in Shenkar the Java Programming course. Its first part focuses in Java. Its second part focuses in Scala. The highlight is Scala. You can find the detailed syllabus at http://www.lifemichael.com/shenkar/SHENKAR_BASIC_JAVA_201302.pdf. You can find the google group we are going to use during this course at https://groups.google.com/forum/?fromgroups#!forum/shenkar-java-scala-2013-03. You can find the [...]
During 2013 spring semester I will deliver in HIT the ‘Internet Programming’ course. Its first part focuses in Java. Its second part focuses in Scala. You can find the detailed syllabus at http://www.lifemichael.com/hit/internet_programming_2013_02_en.pdf. You can find the google group we are going to use during this course at https://groups.google.com/forum/?fromgroups#!forum/hit-scala-2013-02. You can find the on-line detailed plan at https://docs.google.com/spreadsheet/pub?key=0AhDgrQD6qivLdEFGdTJYQjQ3ek5OTDlORjdXSnIxY3c&output=html.
When defining a variable of a generic type we can use a wild card instead of specifying the exact secondary type the generic type uses. object HelloSample { def main(args:Array[String]):Unit = { val a:MyStack[SportCar] = new MyStack[SportCar]; val b:MyStack[_ <: Car] = a; } } class Car class SportCar extends Car class MyStack[T] The following [...]
When using generics Scala doesn’t support covariance. The following code doesn’t compile. object HelloSample { def main(args:Array[String]):Unit = { val a:MyStack[SportCar] = new MyStack[SportCar]; val b:MyStack[Car] = a; } } class Car class SportCar extends Car class MyStack[T] The following video clip shows the compilation error we get while trying to compile this code and [...]
Function values are treated as objects. The function A=>B is an abbreviation for using a new object instantiated from a class that extends the scala.Function1[A,B] trait and overrides the apply function. There are currently Function1, Function2, Function3… etc… up to Function22, that takes 22 parameters. The following code sample shows that. object HelloSample { def main(args:Array[String]):Unit [...]
Scala allows us to define anonymous inner classes. The syntax is very similar to the one we know in Java. object Demo { def main(args:Array[String]):Unit = { val ob = new MyStack[Int](0) { def data:Nothing = throw new Exception(“empty stack”); } } } abstract class MyStack[T](size:Int) { def data:T; } The following video clip overviews [...]
The Scala programming language allows us to define generic functions. This code sample shows that. object Sample { def main(args:Array[String]):Unit = { val ob = getMyStack[Int](10) } def getMyStack[T](num:Int) = { new MyStack[T](num) } } class MyStack[T](size:Int) { //… } The following video clips overviews this code sample, shows its execution and provides more information.
When overloading an unary operators in Scala we should precede the operator name with ‘unary_’. Not doing so we will get an exception when using it. The following code sample shows that. package il.ac.hit.samples object Program { def main(args: Array[String]) { val ob = new RationalNumber(1,3) val other = -ob println(other) } } class RationalNumber(a:Int,b:Int) [...]
When calling a function and passing over an argument which is an expression that needs to be evaluated, the expression will be evaluated before the function is invoked and its value will be passed over. This is the default behavior. By adding => in between the parameter name and its type we will defer the [...]
If the last action a function performs is calling to itself then it is a tail recursive function. When a tail recursive function is executed the computer doesn’t need to keep the memory stack frames. It can use one frame only. Using the @tailrec annotation we can instruct the computer to use one frame only [...]
