The Ring programming language version 1.2 book - Part 11 of 84
0 likes95 views
The document provides documentation on Ring programming language features including for loops, exceptions handling, getting user input, functions, program structure, and lists. It contains examples and explanations of Ring syntax for these features. For loops can iterate over a range or list with optional step values. Functions can accept parameters, return values, and be called recursively. Lists can be created and manipulated using standard list functions and operators. The document is a reference for Ring language elements.
![Ring Documentation, Release 1.2
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
17.3 Exceptions
17.3. Exceptions 80](https://image.slidesharecdn.com/101ringring-170217110601/85/The-Ring-programming-language-version-1-2-book-Part-11-of-84-1-320.jpg)
![CHAPTER
NINETEEN
FUNCTIONS
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
19.1 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
19.2 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:
84](https://image.slidesharecdn.com/101ringring-170217110601/85/The-Ring-programming-language-version-1-2-book-Part-11-of-84-5-320.jpg)
![Ring Documentation, Release 1.2
# 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
19.6 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.
19.7 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:
19.6. Variables Scope 86](https://image.slidesharecdn.com/101ringring-170217110601/85/The-Ring-programming-language-version-1-2-book-Part-11-of-84-7-320.jpg)
![CHAPTER
TWENTYONE
LISTS
In this chapter we are going to learn how to deal with lists.
21.1 Create Lists
We can create new lists by defining the list items inside square bracts.
Example:
aList = [1,2,3,4,5]
Also we can create new lists using the : operator
Example:
aList = 1:5
aList2 = "a":"z"
Example:
aList = 5:1
aList2 = "z":"a"
Also we can create lists using the list() function
Syntax:
list = list(size)
Example
aList = list(10) # aList contains 10 items
Note: the list index start from 1
21.2 Add Items
To add new items to the list, we can use the Add() function.
Syntax:
Add(List,Item)
89](https://image.slidesharecdn.com/101ringring-170217110601/85/The-Ring-programming-language-version-1-2-book-Part-11-of-84-10-320.jpg)
The Ring programming language version 1.2 book - Part 11 of 84
- 1. Ring Documentation, Release 1.2 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 17.3 Exceptions 17.3. Exceptions 80
- 2. Ring Documentation, Release 1.2 try { Block of statements catch Block of statements } 17.3. Exceptions 81
- 3. CHAPTER EIGHTEEN GETTING INPUT We can get input from the keyboard using • The Give Command • The GetChar() Function • The Input() Function 18.1 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 18.2 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() 82
- 4. Ring Documentation, Release 1.2 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 18.3 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 18.3. Input() Function 83
- 5. CHAPTER NINETEEN FUNCTIONS 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 19.1 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 19.2 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: 84
- 6. Ring Documentation, Release 1.2 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 19.3 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 19.4 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 19.5 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: 19.3. Declare parameters 85
- 7. Ring Documentation, Release 1.2 # 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 19.6 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. 19.7 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: 19.6. Variables Scope 86
- 8. Ring Documentation, Release 1.2 if novalue() = NULL See "the function doesn't return a value" + nl ok func novalue 19.8 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 = 1 return 1 else return x * fact(x-1) ok 19.8. Recursion 87
- 9. CHAPTER TWENTY PROGRAM STRUCTURE In this chapter we will learn about using many source code files in the same project. 20.1 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. 20.2 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 88
- 10. CHAPTER TWENTYONE LISTS In this chapter we are going to learn how to deal with lists. 21.1 Create Lists We can create new lists by defining the list items inside square bracts. Example: aList = [1,2,3,4,5] Also we can create new lists using the : operator Example: aList = 1:5 aList2 = "a":"z" Example: aList = 5:1 aList2 = "z":"a" Also we can create lists using the list() function Syntax: list = list(size) Example aList = list(10) # aList contains 10 items Note: the list index start from 1 21.2 Add Items To add new items to the list, we can use the Add() function. Syntax: Add(List,Item) 89