The Ring programming language version 1.10 book - Part 28 of 212
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This document provides documentation on control structures and functions in Ring programming language. It covers the following topics: 1. Branching structures like if/else statements and switch statements. Looping structures like while, for, and for-in loops. Exceptions handling using try/catch. 2. Defining and calling functions. Declaring function parameters. Sending parameters to functions. Main function and variable scope. Returning values from functions. Recursive functions. 3. Getting input using the Give command, GetChar() function, and Input() function.
![Ring Documentation, Release 1.10
for identifier=expression to expression [step expression]
Block of statements
end
Example:
# print numbers from 1 to 10
for x = 1 to 10 put x + nl end
Example:
# Dynamic loop
Put "Start : " get nStart
Put "End : " get nEnd
Put "Step : " get nStep
For x = nStart to nEnd Step nStep
Put x + nl
End
Example:
# print even numbers from 0 to 10
for x = 0 to 10 step 2
Put x + nl
end
Example:
# print even numbers from 10 to 0
for x = 10 to 0 step -2
put x + nl
end
• For in Loop
Syntax:
for identifier in List/String [step expression]
Block of statements
end
Example:
aList = 1:10 # create list contains numbers from 1 to 10
for x in aList put x + nl end # print numbers from 1 to 10
24.3 Exceptions
try
Block of statements
catch
Block of statements
end
24.3. Exceptions 239](https://image.slidesharecdn.com/271ring-190427173217/85/The-Ring-programming-language-version-1-10-book-Part-28-of-212-2-320.jpg)
![Ring Documentation, Release 1.10
(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")
}
25.2. Looping 242](https://image.slidesharecdn.com/271ring-190427173217/85/The-Ring-programming-language-version-1-10-book-Part-28-of-212-5-320.jpg)
![Ring Documentation, Release 1.10
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
25.3 Exceptions
25.3. Exceptions 243](https://image.slidesharecdn.com/271ring-190427173217/85/The-Ring-programming-language-version-1-10-book-Part-28-of-212-6-320.jpg)
![CHAPTER
TWENTYSEVEN
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
27.1 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
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:
247](https://image.slidesharecdn.com/271ring-190427173217/85/The-Ring-programming-language-version-1-10-book-Part-28-of-212-10-320.jpg)
The Ring programming language version 1.10 book - Part 28 of 212
- 1. Ring Documentation, Release 1.10 Example: Put " Main Menu --------- (1) Say Hello (2) About (3) Exit " Get nOption Switch nOption Case 1 Put "Enter your name : " Get name Put "Hello " + name + nl Case 2 Put "Sample : using switch statement" + nl Case 3 Bye Else Put "bad option..." + nl End 24.2 Looping • While Loop Syntax: while Expression Block of statements end Example: While True Put " Main Menu --------- (1) Say Hello (2) About (3) Exit " Get nOption Switch nOption Case 1 Put "Enter your name : " Get name Put "Hello " + name + nl Case 2 Put "Sample : using while loop" + nl Case 3 Bye Else Put "bad option..." + nl End End • For Loop Syntax: 24.2. Looping 238
- 2. Ring Documentation, Release 1.10 for identifier=expression to expression [step expression] Block of statements end Example: # print numbers from 1 to 10 for x = 1 to 10 put x + nl end Example: # Dynamic loop Put "Start : " get nStart Put "End : " get nEnd Put "Step : " get nStep For x = nStart to nEnd Step nStep Put x + nl End Example: # print even numbers from 0 to 10 for x = 0 to 10 step 2 Put x + nl end Example: # print even numbers from 10 to 0 for x = 10 to 0 step -2 put x + nl end • For in Loop Syntax: for identifier in List/String [step expression] Block of statements end Example: aList = 1:10 # create list contains numbers from 1 to 10 for x in aList put x + nl end # print numbers from 1 to 10 24.3 Exceptions try Block of statements catch Block of statements end 24.3. Exceptions 239
- 3. CHAPTER TWENTYFIVE CONTROL STRUCTURES - THIRD STYLE In this chapter we are going to learn about the third style of control structures provided by the Ring programming language. 25.1 Branching • If Statement Syntax: if Expression { Block of statements elseif Expression Block of statements else Block of statements } Example: Load "stdlib.ring" print(" Main Menu --------- (1) Say Hello (2) About (3) Exit ") nOption = getnumber() if nOption = 1 { print("Enter your name : ") name = getstring() print("Hello #{name}n") elseif nOption = 2 print("Sample : using if statementn") elseif nOption = 3 bye else print("bad option...n") } 240
- 4. Ring Documentation, Release 1.10 • 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") } 25.2 Looping • While Loop Syntax: while Expression { Block of statements } Example: Load "stdlib.ring" While True { print(" Main Menu --------- 25.2. Looping 241
- 5. Ring Documentation, Release 1.10 (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") } 25.2. Looping 242
- 6. Ring Documentation, Release 1.10 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 25.3 Exceptions 25.3. Exceptions 243
- 7. Ring Documentation, Release 1.10 try { Block of statements catch Block of statements } 25.3. Exceptions 244
- 8. CHAPTER TWENTYSIX GETTING INPUT We can get input from the keyboard using • The Give Command • The GetChar() Function • The Input() Function 26.1 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 26.2 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() 245
- 9. Ring Documentation, Release 1.10 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 26.3 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 26.3. Input() Function 246
- 10. CHAPTER TWENTYSEVEN 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 27.1 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 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: 247