# Functions - Third Style

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

• Define functions
• Call functions
• Declare parameters
• Send parameters
• Main Function
• Variables Scope
• Return Value
• Recursion

## Define Functions

To define new function

Syntax:

```func <function_name> [parameters] ['{']
Block of statements
['}']
```

Example:

```load "stdlib.ring"
func hello {
print("Hello from function \n")
}
```

## 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:

```load "stdlib.ring"

hello()

func hello {
print("Hello from function \n")
}
```

Example:

```load "stdlib.ring"

first()  second()

func first {  print("message from the first function \n")  }

func second { print("message from the second function \n") }
```

## 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:

```load "stdlib.ring"

func sum(x,y) {
print(x+y)
}
```

## Send Parameters

To send parameters to function, type the parameters inside () after the function name

Syntax:

```funcname(parameters)
```

Example:

```/* output
** 8
** 3000
*/

sum(3,5) sum(1000,2000)

func sum(x,y) { print(x+y) }
```

## 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:

```# this program will print the hello world message first then execute the main function

print("Hello, World! \n")

func main {
print("Message from the main function \n")
}
```

## 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:

```# the program will print numbers from 10 to 1

x = 10                          # x is a global variable.

func main {
for t = 1 to 10 {       # t is a local variable
mycounter()     # call function
}
}

func mycounter {
print("#{x}\n")         # print the global variable value
x--                     # decrement
}
```

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.

## Return Value

The function can return a value using the Return command.

Syntax:

```Return [Expression]
```

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:

```load "stdlib.ring"

if novalue() = NULL {
print("the function doesn't return a value\n")
}

func novalue { }
```

## Recursion

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

Example:

```load "stdlib.ring"

print( fact(5) )        # output = 120

func fact(x) { if x = 0 { return 1 else return x * fact(x-1) } }
```