The Ring programming language version 1.3 book - Part 13 of 88

Ring Documentation, Release 1.3
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
19.3 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
19.3. Input() Function 98

CHAPTER
TWENTY
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
20.1 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
20.2 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:
99

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
20.3 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
20.4 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
20.5 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:
20.3. Declare parameters 100

# 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
20.6 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.
20.7 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:
20.6. Variables Scope 101

if novalue() = NULL
See "the function doesn't return a value" + nl
ok
func novalue
20.8 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
20.8. Recursion 102

CHAPTER
TWENTYONE
PROGRAM STRUCTURE
In this chapter we will learn about using many source code files in the same project.
21.1 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.
21.2 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
103

CHAPTER
TWENTYTWO
LISTS
In this chapter we are going to learn how to deal with lists.
22.1 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
22.2 Add Items
To add new items to the list, we can use the Add() function.
Syntax:
Add(List,Item)
104

Example:
aList = ["one","two"]
add(aList,"three")
see aList
Also we can do that using the + operator.
Syntax:
List + item
Example:
aList = 1:10 # create list contains numbers from 1 to 10
aList + 11 # add number 11 to the list
see aList # print the list
22.3 Get List Size
We can get the list size using the len() function
Syntax:
Len(List)
Example:
aList = 1:20 see len(aList) # print 20
22.4 Delete Item From List
To delete an item from the list, we can use the del() function
Syntax:
del(list,index)
Example:
aList = ["one","two","other","three"]
Del(aList,3) # delete item number three
see aList # print one two three
22.5 Get List Item
To get an item from the list, we uses the next syntax
List[Index]
Example:
aList = ["Cairo","Riyadh"]
see "Egypt : " + aList[1] + nl +
"KSA : " + aList[2] + nl
22.3. Get List Size 105

22.6 Set List Item
To set the value of an item inside the list, we can use the next syntax
List[Index] = Expression
Example:
aList = list(3) # create list contains three items
aList[1] = "one" aList[2] = "two" aList[3] = "three"
see aList
22.7 Search
To ﬁnd an item inside the list we can use the ﬁnd() function
Syntax:
Find(List,ItemValue) ---> Item Index
Find(List,ItemValue,nColumn) ---> Search in nColumn, returns the Item Index
Find(List,ItemValue,nColumn,cAttribute) ---> Item Index
Example:
aList = ["one","two","three","four","five"]
see find(aList,"three") # print 3
Example:
mylist = [["one",1],
["two",2],
["three",3]]
see find(mylist,"two",1) + nl # print 2
see find(mylist,2,2) + nl # print 2
Also we can use the binarysearch() function to search in sorted list.
Syntax:
BinarySearch(List,ItemValue) ---> Item Index
BinarySearch(List,ItemValue,nColumn) ---> Search in nColumn, returns the Item Index
Example:
aList = ["one","two","three","four","five"]
aList = sort(aList)
see binarysearch(aList,"three")
Output:
five
four
one
three
two
4
22.6. Set List Item 106

22.8 Sort
We can sort the list using the sort() function.
Syntax:
Sort(List) ---> Sorted List
Sort(List,nColumn) ---> Sorted List based on nColumn
Sort(List,nColumn,cAttribute) ---> Sorted List based on Object Attribute
Example:
aList = [10,12,3,5,31,15]
aList = sort(aList) see aList # print 3 5 10 12 15 31
We can sort list of strings
Example:
mylist = ["mahmoud","samir","ahmed","ibrahim","mohammed"]
see mylist # print list before sorting
mylist = sort(mylist) # sort list
see "list after sort"+nl
see mylist # print ahmed ibrahim mahmoud mohammed samir
We can sort a list based on a speciﬁc column.
Example:
aList = [ ["mahmoud",15000] ,
["ahmed", 14000 ] ,
["samir", 16000 ] ,
["mohammed", 12000 ] ,
["ibrahim",11000 ] ]
aList2 = sort(aList,1)
see aList2
Output:
ahmed
14000
ibrahim
11000
mahmoud
15000
mohammed
12000
samir
16000
22.9 Reverse
We can reverse a list using the reverse() function.
Syntax:
22.8. Sort 107

The Ring programming language version 1.3 book - Part 13 of 88

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The Ring programming language version 1.3 book - Part 13 of 88