The Ring programming language version 1.9 book - Part 28 of 210
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This document discusses functions in Ring programming language. It covers defining functions, calling functions, declaring parameters, sending parameters, main function, variable scope, return values, and recursion. Functions are defined using keywords like 'def' or 'func' followed by the function name and parameters. Parameters are passed within parentheses when calling a function. Variables within a function have local scope, while those outside have global scope. Functions can return values using the 'return' keyword. Recursion allows a function to call itself.
![CHAPTER
TWENTYSEVEN
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
27.1 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
27.2 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:
239](https://image.slidesharecdn.com/271ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-28-of-210-1-320.jpg)
![Ring Documentation, Release 1.9
# 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
27.6 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.
27.7 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:
27.6. Variables Scope 241](https://image.slidesharecdn.com/271ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-28-of-210-3-320.jpg)
![CHAPTER
TWENTYEIGHT
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
28.1 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")
}
28.2 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:
243](https://image.slidesharecdn.com/271ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-28-of-210-5-320.jpg)
![Ring Documentation, Release 1.9
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 valuen")
}
func novalue { }
28.8 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) } }
28.8. Recursion 246](https://image.slidesharecdn.com/271ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-28-of-210-8-320.jpg)
The Ring programming language version 1.9 book - Part 28 of 210
- 1. CHAPTER TWENTYSEVEN 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 27.1 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 27.2 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: 239
- 2. Ring Documentation, Release 1.9 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 27.3 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 27.4 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 27.5 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: 27.3. Declare parameters 240
- 3. Ring Documentation, Release 1.9 # 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 27.6 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. 27.7 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: 27.6. Variables Scope 241
- 4. Ring Documentation, Release 1.9 if novalue() = NULL put "the function doesn't return a value" + nl end def novalue 27.8 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 27.8. Recursion 242
- 5. CHAPTER TWENTYEIGHT 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 28.1 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") } 28.2 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: 243
- 6. Ring Documentation, Release 1.9 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") } 28.3 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) } 28.4 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) } 28.3. Declare parameters 244
- 7. Ring Documentation, Release 1.9 28.5 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: # this program will print the hello world message first then execute the main function load "stdlib.ring" print("Hello, World! n") func main { print("Message from the main function n") } 28.6 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 load "stdlib.ring" 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. 28.7 Return Value The function can return a value using the Return command. Syntax: 28.5. Main Function 245
- 8. Ring Documentation, Release 1.9 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 valuen") } func novalue { } 28.8 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) } } 28.8. Recursion 246
- 9. CHAPTER TWENTYNINE PROGRAM STRUCTURE In this chapter we will learn about using many source code files in the same project. 29.1 Source Code File Sections Each source code file may contains the next sections (in the same order). Source Code File Sections Load Files Statements and Global Variables Functions Packages and Classes The application maybe one or more of files. 29.2 Using Many Source Code Files To include another source file in the project, just use the load command. Syntax: Load "filename.ring" Note: The Load command is executed directly by the compiler in the parsing stage Tip: if you don’t know the file name until the runtime, or you need to use functions to get the file path, just use eval(). Example: # File : Start.ring Load "sub.ring" sayhello("Mahmoud") # File : sub.ring func sayhello cName see "Hello " + cName + nl 247
- 10. Ring Documentation, Release 1.9 29.3 Load Package Using the ‘load’ command we can use many ring source files in the same project But all of these files will share the same global scope We have also the “Load Package” command Using “Load Package” we can load a library (*.ring file) in new global scope This is very useful to create libraries that avoid conflicts in global variables Example: File: loadpackage.ring x = 100 ? "Hello, World!" load package "testloadpackage.ring" ? x test() File: testloadpackage.ring ? "Hello from testloadpackage.ring" x = 1000 test() func test ? x Output: Hello, World! Hello from testloadpackage.ring 1000 100 1000 29.3. Load Package 248