Introduction

Functions allows to cut a program in several parts. That avoids to have a big Main() procedure.
In Gambas, you have got two types of "functions":

• Functions : return a value
• Procedures : Don't return any values.

Procedures

First of all, you have already saw a procedure. Its name is Main() :-) . This procedure is a little special because it is the first procedure that the Gambas interperter starts to read. Here is how to define a procedure :

Sub procedureName(arguments)

End

Arguments allow to pass parameters to the procedure. If you don't need to pass any arguments, then you can let empty brackets. This is an example to show how to use a procedure in a program :

Sub sayHello()

  Print "Hello !"

End

Public Sub Main()

  sayHello()

End

The result is :

This is another example but with arguments this time :

Sub infoUser (firstname As String, age As Integer)

  PRINT "Firstname : " & firstname
  PRINT "Age : " & age

End

Public Sub Main()

  Dim firstname As String
  Dim age As Integer

  Print "What is your name ? "
  Input firstname

  Print "How old are you ?"
  Input age

  infoUser(firstname, age)

End

The result is :

variable names can be the same that variable names of arguments. As you can see, Gambas has no problem with that :-) . But it's important to say that aren't the same variables !

Functions

Functions acts like procedures except they're returning a value. Their use and define are the same that procedures. We must just indicate which value type will be returned. For example, we're going to ask a number from user, and we'll show the square of this number :

Public Sub Main()

  Dim nombre As Integer

  Print "Please type a number : "
  Input nombre

  Print "The square of " & nombre & " is " & carre(nombre)

End

Function carre (nombre As Integer) As Integer

  Return nombre * nombre 'indicate the value that the function returns.

End

To get the returned value of the function, you must declare a variable to store the result.

Accessibility

The Main() procedure is preceded by the PUBLIC keyword. For this procedure, That's its signature. But for procedures that you're defining youself, this keyword allows to define the accessibility of your procedure. I.e, if you have several Gambas modules, that allows you to call these procedures in others modules.

However, if you want procedures and functions are only called in the same module, you must indicate the PRIVATE keyword in front of your procedures and functions.