Gambas--GAMBAS Almost Means BASIC

Gambas is the name of an object-oriented dialect of the BASIC programming language, as well as the integrated development environment that accompanies it. Designed to run on Linux and other Unix-like computer operating systems, its name is a recursive acronym for Gambas Almost Means Basic.Gambas is also the word for prawns in the Spanish and Portuguese languages, from which the project's logos are derived.

Gambas was developed by the French programmer Benoît Minisini, with its first release coming in 1999. Benoît had grown up with the BASIC language, and decided to make a free software development environment that could quickly and easily make programs with user interfaces.

Ckeck whether Gambus is installed if not enter these commands one by one.

sudo add-apt-repository ppa: shrimp-team / gambas3
sudo apt-get update
sudo apt-get install gambas3

Know more about Gambas here http://gambas.sourceforge.net/en/main.html
 http://gambaswiki.org/wiki/tutorial

Developing applications in Gambas

Only will take a few minutes to build your first application in Gambas. The graphic user interface (GUI) will be quickly created by drawing on the form widgets like text boxes or command buttons. Then you will set some properties to the form and widgets to specify values like text, color or size. Finally, some code must be written to bring to life your application. Those basic steps that you'll use to create your first application, will show you the principles that you will use for develop any other application in Gambas.

basic steps to create a Gambas application?

a)Create the interface.

b)Set properties.

c)Write code.

1.- Fire up your Gambas IDE, then on the Welcome screen select New project. This opens the New project Wizard.

2.- On screen 1 select QT graphical application.

3.- Select a location to save your project.

4.- Type a name for your project.

Now you can build a sample application

1,2.Creating the Interface and setting the properties

Design GUI using the toolbox and set the properties

Control	Property	Setting
Label1	Text	“Tell me your name:”
Label1	Alignment	Center
Button1	Text	“&Hello”
TextBox1	Text	“Write your name here”
FormMain	Text	“My first Gambas project”

3.Writing the code

The Code editor is where you write the code for your application. The code is a set of language statements, constants & declarations.

To open the Code editor

Double click over the object you want to write code or on the Resources visor select the name of the form or module and from the contextual menu select Edit class.

To create an event procedure

Select the object.

Double click over the object to write the code for the default event. 

Write the code between the statements PUBLIC SUB & END SUB. For this lesson write the following code:

Label1.Text = "Hello " & Textbox1.Text & ". This is my first Gambas project!".

The code for the procedure must be look like this:

PUBLIC SUB Button1_Click()

Label1.Text = "Hello " & Textbox1.Text & ". This is my first Gambas project!"

END SUB

4.Run the application

Click run button or from debug menu choose run or press F5.

Create a new application with three text boxes.First two will read input data and the third textbox will show the result of arithmetic operations when corresponding button is clicked.Place command buttons for each arithmetic operations.

Variables

Introduction

What is a variable? A variable stores an item that can change. e.g. "Car" can be changed to "Cars", 1 can become 567

Variables in programming are indispensable. We can do nothing without variables. So, imagine a program that asks how old a user is. You may wish to print a message depending on the age of the user.

There are many variables types in Gambas, let's start with a few simple ones.

• Integers - Whole numbers e.g. 1, 14, 897
• Float - Numbers with decimals e.g. 1.2, 10.115, 0.5, 3.142
• String - Text e.g. "What is your name?", "Apple"

A variable name must follow some rules:

• It must never begin by a digit
• It must never contain any spaces
• It must never contain any accented character

Let's practice

How to use a variable? Firstly we must declare it, i.e. "create" it before we can use it.In Visual Basic, it was optional unless you enabled the explicit option.

In Gambas, you must declare all your variables. This is good practice and will help avoid making some mistakes.

This is one way to declare a variable:

Dim MyAge As Integer

You can assign a value like this:

Dim MyAge As Integer = 25

Dim nickname As String

nickname = "NewToGambas" 'This is another way to assign a value

Let's have a look at how to print a variable by using the PRINT command:

' Gambas module file

Public Sub Form_Open()

  Dim nickname As String = "NewToGambas"

  Print "My nickname on internet is " & nickname

End

To concatenate (join together) any String variables, we use the & operator.

It's easy, isn't it?

Work with information from the user

To get some data from the user, we will use the InputBox command.  Here is an example:

' Gambas module file

Public Sub Form_Open()

  Dim nickname As String

  nickname = InputBox("What is your nickname?")

  Print "Your nickname is " & nickname

End

When the program arrives at this line:

nickname = InputBox("What is your nickname?")

It will stop and wait for the data from user and continue when the user presses the Return (or Enter) key.

Test control and loop structures

Without these structures, our programs would work in a sequential way, and would be very poor.

Test structures

This allows us to perform some instructions if a condition is true.

If ... Then

This is the structure the most basic:

If condition Then

Endif

condition is the expression to test. The condition signs are:

• > : purely upper
• < : purely lower
• >= : upper or equal
• <= : lower or equal
• = : equal
• <> : unlike

Thus we can compare two values, two variables for example:

If Variable1 = Variable2 Then

Here, the "=" sign indicates an equality test, and not a value being assigned to a variable (like in a = 1).

Now, Here is an example to show that:

Public Sub Main()
  Dim age As Integer
  Print "How old are you? "
  Input age

  If age >= 18 Then
    Print "You are major."
  Else
    Print "You are minor."
  Endif
End

The ELSE keyword is optional. Example:

' Gambas module file

Public Sub Main()
  Dim power As Integer = 15  'power in ch
  If puissance < 15 Then
    Print "Do you want to change your car? :p "
  Endif
End

Another note, the ENDIF keyword is optional if there is only one instruction to execute:

Public Sub Main()
  Dim power As Integer = 15  'power in ch

  If puissance < 15 Then Print "Do you want to change your car? :p "
End

The Select ... Case structure

We're using this structure when there are many values to test. With this structure, our code is more clear to read:

Public Sub Main()

  Dim pays As string

  Print "De quel pays venez-vous ?"
  Input pays
  pays= lcase(pays) 'remove uppercase

  Select Case pays
     Case "france"
        Print "Bonjour !"
     Case "england"
        Print "Hello!"
     Case "espana"
        Print "Ola!"
     Case "portugal"
        Print "Hola !"
     Case Else
        print"??"
  End Select
End

Loops
Loops allows you to repeat one or more instructions. Three loops type exists allowing you to do the same thing in a different way.

For
The For loop allows to repeat an instructions block n times.

Public Sub Main()
  Dim i As Integer
  For i = 1 To 5
    Print "Value of i: " & i
  Next
End

When Gambas enters the loop for the first time, it applies the value 1 to i, then executes next instructions until it meets the NEXT keyword. Gambas returns to the beginning of loop, then increments the i variable until it reaches 5. The loop instructions will be read 5 times:

Value of i: 1
Value of i: 2
Value of i: 3
Value of i: 4
Value of i: 5

Do ... Loop

Sometimes we don't know the number of loops to do. But we know how it must stop. Here is an example:

Public Sub Main()
  Dim result As integer
  Print "How many two and two?"
  Do
     Input result
  Loop Until result = 4
  PRINT "Congratulation! You have found :-) "
End

We can also use the WHILE keyword instead of UNTIL to make a loop structure with a condition.
Do Input result Loop While result <> 4
While
About WHILE, there is a loop structure specially for While:

' Gambas module file
Public sub Main()
  Dim age As Integer
  While age < 10
    Inc age
    Print "Value of age : " & age
  Wend
End

Result:

Value of age : 1
Value of age : 2
Value of age : 3
Value of age : 4
Value of age : 5
Value of age : 6
Value of age : 7
Value of age : 8
Value of age : 9
Value of age : 10