Ring/Lessons/Functions

Functions
In this chapter we are going to learn about the next topics :-


 * Define functions


 * Call functions


 * Declare parameters


 * Send parameters


 * Main Function


 * Variables Scope


 * Program structure


 * Return Value


 * Recursion

Define Functions
To define new function

Syntax:

.. note:: No keyword is required to end the function definition.

Example:

Call Functions
To call function without parameters, we type the function name then

.. tip:: We can call the function before the function definition and the function code.

Example:

Example:

Declare parameters
To declare the function parameters, after the function name type the list of parameters as a group of identifiers separated by comma.

Example:

Send Parameters
To send parameters to function, type the parameters inside after the function name

Syntax:

Example:

Main Function
Using the Ring programming language, the Main Function is optional, when it's defined, it will be executed after the end of other statements.

if no other statements comes alone, the main function will be the first `entry point `_

Example:

Variables Scope
The Ring programming language uses `lexical scoping `_ to determine the scope of a variable. Variables defined inside functions (including function parameters) are local variables. Variables defined outside functions (before any function) are global variables.

Inside any function we can access the variables defined inside this function beside the global variables.

Example:

.. note:: Using the main function before the for loop declare the t variable as a local variable, It's recommended to use the main functions instead of typing the instructions directly to set the scope of the new variables to local.

Program Structure
The application maybe one or more of files.

to include another source file in the project, just use the load command.

Syntax:

Example:

Return Value
The function can return a value using the Return command.

Syntax:

.. tip:: the Expression after the return command is optional and we can use the return command to end the function execution without returning any value. .. note:: if the function doesn't return explicit value, it will return NULL (empty string = "" ).

Example:

Recursion
The Ring programming language support `Recursion `_ and the function can call itself using different parameters.

Example: