A procedure is a group of reusable code which can be called from anywhere in your program. This eliminates the need of writing same code again and again. This helps programmers to write modular code.

Like any other advance programming language, Euphoria also supports all the features necessary to write modular code using procedures.

You must have seen procedures like printf() and length() in previous chapters. We are using these procedure again and again but they have been written in core Euphoria only once.

Euphoria allows you to write your own procedures as well. This section explains how to write your own procedure in Euphoria.

Procedure Definition

Before you use a procedure, you need to define it. The most common way to define a procedure in Euphoria is by using the procedure keyword, followed by a unique procedure name, a list of parameters (that might be empty), and a statement block which ends with end procedure statement. The basic syntax is as shown below −

procedure procedurename(parameter-list)

   statements
   ..........

end procedure

Example

A simple procedure called sayHello that takes no parameters is defined here −

procedure  sayHello()
   puts(1, "Hello there")
end procedure

Calling a Procedure

To invoke a procedure somewhere later in the script, you simply need to write the name of that procedure as follows −

#!/home/euphoria-4.0b2/bin/eui

procedure  sayHello()
   puts(1, "Hello there")
end procedure 

-- Call above defined procedure.
sayHello()

This produces the following result −

Hello there

Procedure Parameters

Till now you have seen procedure without a parameter. But there is a facility to pass different parameters while calling a procedure. These passed parameters can be captured inside the procedure and any manipulation can be done over those parameters.

A procedure can take multiple parameters separated by comma.

Example

Let us do a bit modification in our sayHello procedure. This time it takes two parameters −

#!/home/euphoria-4.0b2/bin/eui

procedure sayHello(sequence name,atom  age)
   printf(1, "%s is %d years old.", {name, age})
end procedure

-- Call above defined procedure.
sayHello("zara", 8)

This produces the following result −

zara is 8 years old.