The Ring programming language version 1.6 book - Part 23 of 189

1. CHAPTER
TWENTYTHREE
FUNCTIONS - FIRST 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
23.1 Define Functions
To define new function
Syntax:
func <function_name> [parameters]
Block of statements
Note: No keyword is required to end the function definition.
Example:
func hello
see "Hello from function" + nl
23.2 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:
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hello()
func hello
see "Hello from function" + nl
Example:
first() second()
func first see "message from the first function" + nl
func second see "message from the second function" + nl
23.3 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:
func sum x,y
see x+y+nl
23.4 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 see x+y+nl
23.5 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:
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# this program will print the hello world message first then execute the main function
See "Hello World!" + nl
func main
see "Message from the main function" + nl
23.6 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 func-
tions (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
next
func mycounter
see x + nl # 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.
23.7 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:
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if novalue() = NULL
See "the function doesn't return a value" + nl
ok
func novalue
23.8 Recursion
The Ring programming language support Recursion and the function can call itself using different parameters.
Example:
see fact(5) # output = 120
func fact x if x = 0 return 1 else return x * fact(x-1) ok
23.8. Recursion 196

5. CHAPTER
TWENTYFOUR
FUNCTIONS - SECOND 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
24.1 Define Functions
To define new function
Syntax:
def <function_name> [parameters]
Block of statements
[end]
Note: the keyword ‘end’ is optional.
Example:
def hello
put "Hello from function" + nl
end
24.2 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:
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hello()
def hello
put "Hello from function" + nl
end
Example:
first() second()
def first put "message from the first function" + nl
def second put "message from the second function" + nl
24.3 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:
def sum x,y
put x+y+nl
end
24.4 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)
def sum x,y put x+y+nl
24.5 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:
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# this program will print the hello world message first then execute the main function
put "Hello World!" + nl
def main
put "Message from the main function" + nl
end
24.6 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 func-
tions (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.
def main
for t = 1 to 10 # t is a local variable
mycounter() # call function
end
end
def mycounter
put x + nl # print the global variable value
x-- # decrement
end
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.
24.7 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:
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if novalue() = NULL
put "the function doesn't return a value" + nl
end
def novalue
24.8 Recursion
The Ring programming language support Recursion and the function can call itself using different parameters.
Example:
put fact(5) # output = 120
def fact x if x = 0 return 1 else return x * fact(x-1) end
24.8. Recursion 200

9. CHAPTER
TWENTYFIVE
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
25.1 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")
}
25.2 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:
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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") }
25.3 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)
}
25.4 Send Parameters
To send parameters to function, type the parameters inside () after the function name
Syntax:
funcname(parameters)
Example:
/* output
** 8
** 3000
*/
load "stdlib.ring"
sum(3,5) sum(1000,2000)
func sum(x,y) { print(x+y) }
25.3. Declare parameters 202