Function Type in Scala PRO
Scala allows us to define variables, function parameters and function returned values with a type that is a function. We can even specify the exact signature of that function. import annotation.tailrec object Program { def main(args: Array[String]):Unit = { var func:(Int,Int)=>Int = sum; println(func(4,3)) func = multiply println(func(4,3)) } def sum(a:Int,b:Int):Int = a+b def multiply(a:Int,b:Int):Int […]
Tail Recursive Function in Scala PRO
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 […]
Multiple Lines Expressions in Scala PRO
When having an expression that spans over more than one line the compiler might evaluate the expression while avoiding parts of the expression. We can overcome this problem in two ways. This video clip explains this issue.
Blocks in Scala PRO
The definitions within a block are visible from within the block only. The definitions within a block shadow definitions with the same names that belong to the block’s outer scope. The block has a value just as any other expression. Its value is the value of the last expression it includes. object Program { def […]
Scala Worksheet using IntelliJPRO
The following short video clip shows how to create a Scala worksheet when using the IntelliJ IDE. Using a worksheet we can strength our understanding of the Scala programming language.
The Returned Type of Recursive Function in Scala PRO
When you define a recursive function you must specify the type of the returned value. If you don’t do it the compilation fails. object Program { def main(args: Array[String]):Unit = { println(factorial(4)) } def factorial(num:Int):Int = if (num==0) 1 else num*factorial(num-1) } The following video clip explains that.
Scala Expressions Evaluation PRO
When creating a variable using val or var and assigning the value of an expression into it the expression is evaluated when the variable is created. When creating a function using def and assigning the value of an expression to it the expression is evaluated when calling the function. object Program { def main(args: Array[String]):Unit […]
Node.js on Cloud9 Jump Start PRO
Node.js is a platform built on top of JavaScript v.8, Google’s JavaScript runtime engine. Node.js enables us to develop web applications that excellent in their performance. The following code sample is a simple HTTP web server developed using node.js that returns the hello greeting back to the client from which the HTTP request arrives. var […]
Log4j Jump Start PRO
Log4j is an open source project developed and maintained by Apache. It is part of a bigger open source project known as the Apache Logging Services. The following code sample shows how to use Log4j in its basic configuration. package il.ac.hit.samples; import org.apache.log4j.BasicConfigurator; import org.apache.log4j.Logger; public class SimpleLoop { static Logger logger = Logger.getLogger(“SimpleLoop”); public […]
WordPress Jump Start Lecture INFO
On Tuesday November 27th I delivered a practical jump start for websites development using the WordPress open source project. You can find the detailed presentation I was using during the lecture ready for download at http://www.lifemichael.com/presentations/wordpressjumpstart.pdf. I have just complete to prepare a series of short video clips (in hebrew) you can watch for free and […]