1 Gentle Introduction to Programming Tirgul 1: Shell and Scala “hands on” in the lab

2 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

3 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

4 Your Account, Basic Linux Commands User’s account: to log in select session: GNOME Web browser Open the “system handouts” file from the course’s site (in the session’s section) Shell / Console

5 Basic Linux Commands

6 Security (chmod)

7 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

8 Using the Interpreter Type “scala” from the console Start trying some basic commands: println(“hello world!”) val x = 5 var y = 1.4 Define a function that receives two integers and return their sum. Use it on several inputs.

9 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

10 Eclipse Type “eclipse35 &” from the console Use a workspace located on your account How to solve common technical problems: “ Clean” your eclipse by removing the.eclipse directory (rm –R.eclipse, from your root) Start a new workspace / remove the old one

11 Open Eclipse – Set Workspace

12 Open Eclipse

13 Define New Project

14 If you don’t find the Scala new project… File  New  Project

15 New Object

16 Write Some Code

17 Run output

18 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

19 Understanding Compiler Messages Open the interpreter, try the following lines of code, and try to understand what the compiler means, and how to solve it val x = 5 x = 6 Println(“123”) val f = (x : Int => x + 1) if x > f(x) x = 9 val f = (x : int) => x + 1

20 And In Eclipse Select and copy a program of your choice to Eclipse How are compilation errors marked in Eclipse? Perform compilation errors purposely and see how the compiler’s errors look like: Change an upper-case letter to lower case Remove a closing brackets Where are the compiled files?

21 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

22 Command Line Arguments In Eclipse

23 Command Line Arguments In Eclipse

24 Usage Example ? Fibonacci.scala

25 Example: Prime Write a program that receives from the command line arguments a list of numbers, and prints out for each whether it is prime Use the prime code that is published, and wrap it as a function Notice, that the number of arguments is not known in advance!

26 The Debugger Some programs may compile correctly, yet not produce the desirable results These programs are valid and correct Scala programs, yet not the programs we meant to write! The debugger can be used to follow the program step by step and may help detecting bugs in an already compiled program

27 Debugger – Add Breakpoint Right click on the desired line “Toggle Breakpoint”

28 Debugger – Start Debugging breakpoint debug

29 Debugger – Debug Perspective

30 Debugger – Debugging Current state Current location Back to Scala perspective

31 Today Login to your account Your Account, basic Linux commands Using the interpreter Eclipse – “Hello World!” Understanding compiler messages Eclipse: Command line arguments Debugger Home work – practice Shell commands

32 Home Work - Shell