The Ring programming language version 1.9 book - Part 27 of 210
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The document discusses functions in Ring programming language. Some key points: 1. Functions are defined using func keyword followed by function name and parameters. Functions can be called before definition. 2. Parameters are declared within function definition and passed within parentheses when calling. 3. Variables within functions are local, variables outside are global. Local variables are only accessible within the function. 4. Functions can return a value using return statement. If no return, NULL is returned. 5. Recursion is supported where a function can call itself, such as factorial example.
![Ring Documentation, Release 1.9
(1) Say Hello
(2) About
(3) Exit
")
nOption = GetString()
switch nOption {
case 1
print("Enter your name : ")
name = getstring()
print("Hello #{name}n")
case 2
print("Sample : using switch statementn")
case 3
Bye
else
print("bad option...n")
}
}
• For Loop
Syntax:
for identifier=expression to expression [step expression] {
Block of statements
}
Example:
# print numbers from 1 to 10
load "stdlib.ring"
for x = 1 to 10 {
print("#{x}n")
}
Example:
load "stdlib.ring"
# Dynamic loop
print("Start : ") nStart = getnumber()
print("End : ") nEnd = getnumber()
print("Step : ") nStep = getnumber()
for x = nStart to nEnd step nStep {
print("#{x}n")
}
Example:
load "stdlib.ring"
# print even numbers from 0 to 10
for x = 0 to 10 step 2 {
print("#{x}n")
}
24.2. Looping 230](https://image.slidesharecdn.com/261ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-27-of-210-2-320.jpg)
![Ring Documentation, Release 1.9
Example:
load "stdlib.ring"
# print even numbers from 10 to 0
for x = 10 to 0 step -2 {
print("#{x}n")
}
• For in Loop
Syntax:
for identifier in List/String [step expression] {
Block of statements
}
Example:
load "stdlib.ring"
aList = 1:10 # create list contains numbers from 1 to 10
for x in aList { print("#{x}n") } # print numbers from 1 to 10
Example:
load "stdlib.ring"
aList = 1:10 # create list contains numbers from 1 to 10
# print odd items inside the list
for x in aList step 2 {
print("#{x}n")
}
When we use (For in) we get items by reference.
This means that we can read/edit items inside the loop.
Example:
load "stdlib.ring"
aList = 1:5 # create list contains numbers from 1 to 5
# replace list numbers with strings
for x in aList {
switch x {
case 1 x = "one"
case 2 x = "two"
case 3 x = "three"
case 4 x = "four"
case 5 x = "five"
}
}
print(aList) # print the list items
24.3 Exceptions
24.3. Exceptions 231](https://image.slidesharecdn.com/261ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-27-of-210-3-320.jpg)
![CHAPTER
TWENTYSIX
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
26.1 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
26.2 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:
235](https://image.slidesharecdn.com/261ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-27-of-210-7-320.jpg)
![Ring Documentation, Release 1.9
# 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
26.6 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.
26.7 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:
26.6. Variables Scope 237](https://image.slidesharecdn.com/261ring-181106093618/85/The-Ring-programming-language-version-1-9-book-Part-27-of-210-9-320.jpg)
The Ring programming language version 1.9 book - Part 27 of 210
- 1. Ring Documentation, Release 1.9 • Switch Statement Syntax: switch Expression { case Expression Block of statements else Block of statements } Example: Load "stdlib.ring" print(" Main Menu --------- (1) Say Hello (2) About (3) Exit ") nOption = GetString() switch nOption { case 1 print("Enter your name : ") name = getstring() print("Hello #{name}n") case 2 print("Sample : using switch statementn") case 3 Bye else print("bad option...n") } 24.2 Looping • While Loop Syntax: while Expression { Block of statements } Example: Load "stdlib.ring" While True { print(" Main Menu --------- 24.2. Looping 229
- 2. Ring Documentation, Release 1.9 (1) Say Hello (2) About (3) Exit ") nOption = GetString() switch nOption { case 1 print("Enter your name : ") name = getstring() print("Hello #{name}n") case 2 print("Sample : using switch statementn") case 3 Bye else print("bad option...n") } } • For Loop Syntax: for identifier=expression to expression [step expression] { Block of statements } Example: # print numbers from 1 to 10 load "stdlib.ring" for x = 1 to 10 { print("#{x}n") } Example: load "stdlib.ring" # Dynamic loop print("Start : ") nStart = getnumber() print("End : ") nEnd = getnumber() print("Step : ") nStep = getnumber() for x = nStart to nEnd step nStep { print("#{x}n") } Example: load "stdlib.ring" # print even numbers from 0 to 10 for x = 0 to 10 step 2 { print("#{x}n") } 24.2. Looping 230
- 3. Ring Documentation, Release 1.9 Example: load "stdlib.ring" # print even numbers from 10 to 0 for x = 10 to 0 step -2 { print("#{x}n") } • For in Loop Syntax: for identifier in List/String [step expression] { Block of statements } Example: load "stdlib.ring" aList = 1:10 # create list contains numbers from 1 to 10 for x in aList { print("#{x}n") } # print numbers from 1 to 10 Example: load "stdlib.ring" aList = 1:10 # create list contains numbers from 1 to 10 # print odd items inside the list for x in aList step 2 { print("#{x}n") } When we use (For in) we get items by reference. This means that we can read/edit items inside the loop. Example: load "stdlib.ring" aList = 1:5 # create list contains numbers from 1 to 5 # replace list numbers with strings for x in aList { switch x { case 1 x = "one" case 2 x = "two" case 3 x = "three" case 4 x = "four" case 5 x = "five" } } print(aList) # print the list items 24.3 Exceptions 24.3. Exceptions 231
- 4. Ring Documentation, Release 1.9 try { Block of statements catch Block of statements } 24.3. Exceptions 232
- 5. CHAPTER TWENTYFIVE GETTING INPUT We can get input from the keyboard using • The Give Command • The GetChar() Function • The Input() Function 25.1 Give Command Syntax: Give VariableName Example: See "Enter the first number : " Give nNum1 See "Enter the second number : " Give nNum2 See "Sum : " + ( 0 + nNum1 + nNum2 ) Output: Enter the first number : 3 Enter the second number : 4 Sum : 7 25.2 GetChar() Function We can get one character from the standard input using the GetChar() function Syntax: GetChar() ---> Character Example: While True See " Main Menu (1) Say Hello (2) Exit " Option = GetChar() 233
- 6. Ring Documentation, Release 1.9 GetChar() GetChar() # End of line # the previous two lines can be replaced with the next line # Give Option if Option = 1 see "Enter your name : " give cName see "Hello " + cName else bye ok End 25.3 Input() Function We can get input from the keyboard using the Input() function Syntax: Input(nCount) ---> string The function will wait until nCount characters (at least) are read Example: See "Enter message (30 characters) : " cMsg = input(30) See "Message : " + cMsg 25.3. Input() Function 234
- 7. CHAPTER TWENTYSIX 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 26.1 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 26.2 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: 235
- 8. Ring Documentation, Release 1.9 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 26.3 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 26.4 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 26.5 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: 26.3. Declare parameters 236
- 9. Ring Documentation, Release 1.9 # 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 26.6 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. 26.7 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: 26.6. Variables Scope 237
- 10. Ring Documentation, Release 1.9 if novalue() = NULL See "the function doesn't return a value" + nl ok func novalue 26.8 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 26.8. Recursion 238