The Ring programming language version 1.5.3 book - Part 22 of 184
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This document provides summaries of key features of lists in Ring programming language. Lists allow storing multiple values in a single variable. Key points include: - Lists can be created using square brackets or : operator and items can be added or removed. - Functions like len(), find(), sort(), reverse() etc. allow getting length, searching, sorting and reversing lists. - Lists support nested structures and can be passed to and returned from functions. - String indices can be used to access items in lists containing pairs of string and values. - Lists provide a way to pass variable number of parameters to functions in a flexible order.
![Ring Documentation, Release 1.5.3
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 { }
24.8 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) } }
24.8. Recursion 185](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-1-320.jpg)
![CHAPTER
TWENTYSIX
LISTS
In this chapter we are going to learn how to deal with lists.
26.1 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
26.2 Add Items
To add new items to the list, we can use the Add() function.
Syntax:
Add(List,Item)
187](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-3-320.jpg)
![Ring Documentation, Release 1.5.3
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
26.3 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
26.4 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
26.5 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
26.3. Get List Size 188](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-4-320.jpg)
![Ring Documentation, Release 1.5.3
26.6 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
26.7 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
26.6. Set List Item 189](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-5-320.jpg)
![Ring Documentation, Release 1.5.3
26.8 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
26.9 Reverse
We can reverse a list using the reverse() function.
Syntax:
26.8. Sort 190](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-6-320.jpg)
![Ring Documentation, Release 1.5.3
Reverse(List) ---> Reversed List
Example:
aList = [10,20,30,40,50]
aList = reverse(aList)
see aList # print 50 40 30 20 10
26.10 Insert Items
To insert an item in the list we can use the insert() function.
Syntax:
Insert(List,Index,Item)
The inserted item will be AFTER the Index
Example:
aList = ["A","B","D","E"]
insert(aList,2,"C") # Inserts AFTER Index 2, "C" into Position 3
see aList # print A B C D E
26.11 Nested Lists
The list may contain other lists
Example:
aList = [ 1 , [10,20,30] , 5 , [100,1000,5000] ]
aList2 = [
"one","two",
[3,4],
[20,30], ["three",
"four",
"five",[100,200,300]
]
]
see aList[2] # print 10 20 30
see aList[4][3] + nl # print 5000
see aList2[5][2] + nl # print four
see aList2[5][4][3] # print 300
26.12 Copy Lists
We can copy lists (including nested lists) using the Assignment operator.
Example:
26.10. Insert Items 191](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-7-320.jpg)
![Ring Documentation, Release 1.5.3
aList = [
"one","two",
[3,4],
[20,30], ["three",
"four",
"five",[100,200,300]
]
]
aList2 = aList # Copy aList to aList2
aList2[5] = "other" # modify item number five
see aList2[5] + nl # print other
see aList[5] # print three four five 100 200 300
26.13 First-class lists
Lists are first-class citizens where we can store lists in variables, pass lists to functions, and return lists from functions.
Example:
aList = duplicate( [1,2,3,4,5] )
see aList[10] + nl # print 5
see mylist() # print 10 20 30 40 50
func duplicate list
nMax = len(list)
for x = 1 to nMax
list + list[x]
next
return list
func mylist return [10,20,30,40,50]
26.14 Using Lists during definition
We can use the list items while we are defining the list for the first time.
Example:
aList = [ [1,2,3,4,5] , aList[1] , aList[1] ]
see aList # print 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5
26.15 Passing Lists to Functions
Lists are passed to functions by reference, This means that the called function will work on the same list and can
modify it.
Example:
func main
aList = [1,2,3,4,5] # create list, local in function main
26.13. First-class lists 192](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-8-320.jpg)
![Ring Documentation, Release 1.5.3
myfunc(aList) # call function, pass list by reference
see aList # print 1 2 3 4 5 6 7 8 9 10
func myfunc list
list + [6,7,8,9,10]
26.16 Access List Items by String Index
Instead of using numbers to determine the item index when we get item value or set item value, We can access items
using string index if the item is a list contains two items and the first item is a string.
Example:
aList = [ ["one",1] , ["two",2] , ["three",3] ]
see aList["one"] + nl +
aList["two"] + nl +
aList["three"] # print 1 2 3
This type of lists can be defined in a better syntax using the : and = operators.
Example:
aList = [ :one = 1 , :two = 2 , :three = 3 ]
see aList["one"] + nl +
aList["two"] + nl +
aList["three"] + nl # print 1 2 3
see aList[1] # print one 1
Tip: using : before identifier (one word) means literal
Note: using = inside list definition create a list of two items where the first item is the left side and the second item is
the right side.
We can add new items to the list using the string index
Example:
aList = []
aList["Egypt"] = "Cairo"
aList["KSA"] = "Riyadh"
see aList["Egypt"] + nl + # print Cairo
aList["KSA"] + nl # print Riyadh
26.17 Passing Parameters Using List
This type of lists is very good for passing parameters to functions Where the order of parameters will not be important
(we can change the order).
Also some parameters maybe optional.
Example:
26.16. Access List Items by String Index 193](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-9-320.jpg)
![Ring Documentation, Release 1.5.3
myconnect ( [ :server = "myserver.com" , :port = 80 ,
:username = "mahmoud" , :password = "password" ] )
func myconnect mypara
# print connection details
see "User Name : " + mypara[:username] + nl +
"Password : " + mypara[:password] + nl +
"Server : " + mypara[:server] + nl +
"Port : " + mypara[:port]
26.18 Swap Items
We can swap the list items using the Swap() function.
Example:
aList = [:one,:two,:four,:three]
see aList
see copy("*",50) + nl
swap(aList,3,4)
see aList
Output
one
two
four
three
**************************************************
one
two
three
four
26.18. Swap Items 194](https://image.slidesharecdn.com/211fayedringdoc1-180327101417/85/The-Ring-programming-language-version-1-5-3-book-Part-22-of-184-10-320.jpg)
The Ring programming language version 1.5.3 book - Part 22 of 184
- 1. Ring Documentation, Release 1.5.3 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 { } 24.8 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) } } 24.8. Recursion 185
- 2. CHAPTER TWENTYFIVE PROGRAM STRUCTURE In this chapter we will learn about using many source code files in the same project. 25.1 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. 25.2 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 186
- 3. CHAPTER TWENTYSIX LISTS In this chapter we are going to learn how to deal with lists. 26.1 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 26.2 Add Items To add new items to the list, we can use the Add() function. Syntax: Add(List,Item) 187
- 4. Ring Documentation, Release 1.5.3 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 26.3 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 26.4 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 26.5 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 26.3. Get List Size 188
- 5. Ring Documentation, Release 1.5.3 26.6 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 26.7 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 26.6. Set List Item 189
- 6. Ring Documentation, Release 1.5.3 26.8 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 26.9 Reverse We can reverse a list using the reverse() function. Syntax: 26.8. Sort 190
- 7. Ring Documentation, Release 1.5.3 Reverse(List) ---> Reversed List Example: aList = [10,20,30,40,50] aList = reverse(aList) see aList # print 50 40 30 20 10 26.10 Insert Items To insert an item in the list we can use the insert() function. Syntax: Insert(List,Index,Item) The inserted item will be AFTER the Index Example: aList = ["A","B","D","E"] insert(aList,2,"C") # Inserts AFTER Index 2, "C" into Position 3 see aList # print A B C D E 26.11 Nested Lists The list may contain other lists Example: aList = [ 1 , [10,20,30] , 5 , [100,1000,5000] ] aList2 = [ "one","two", [3,4], [20,30], ["three", "four", "five",[100,200,300] ] ] see aList[2] # print 10 20 30 see aList[4][3] + nl # print 5000 see aList2[5][2] + nl # print four see aList2[5][4][3] # print 300 26.12 Copy Lists We can copy lists (including nested lists) using the Assignment operator. Example: 26.10. Insert Items 191
- 8. Ring Documentation, Release 1.5.3 aList = [ "one","two", [3,4], [20,30], ["three", "four", "five",[100,200,300] ] ] aList2 = aList # Copy aList to aList2 aList2[5] = "other" # modify item number five see aList2[5] + nl # print other see aList[5] # print three four five 100 200 300 26.13 First-class lists Lists are first-class citizens where we can store lists in variables, pass lists to functions, and return lists from functions. Example: aList = duplicate( [1,2,3,4,5] ) see aList[10] + nl # print 5 see mylist() # print 10 20 30 40 50 func duplicate list nMax = len(list) for x = 1 to nMax list + list[x] next return list func mylist return [10,20,30,40,50] 26.14 Using Lists during definition We can use the list items while we are defining the list for the first time. Example: aList = [ [1,2,3,4,5] , aList[1] , aList[1] ] see aList # print 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 26.15 Passing Lists to Functions Lists are passed to functions by reference, This means that the called function will work on the same list and can modify it. Example: func main aList = [1,2,3,4,5] # create list, local in function main 26.13. First-class lists 192
- 9. Ring Documentation, Release 1.5.3 myfunc(aList) # call function, pass list by reference see aList # print 1 2 3 4 5 6 7 8 9 10 func myfunc list list + [6,7,8,9,10] 26.16 Access List Items by String Index Instead of using numbers to determine the item index when we get item value or set item value, We can access items using string index if the item is a list contains two items and the first item is a string. Example: aList = [ ["one",1] , ["two",2] , ["three",3] ] see aList["one"] + nl + aList["two"] + nl + aList["three"] # print 1 2 3 This type of lists can be defined in a better syntax using the : and = operators. Example: aList = [ :one = 1 , :two = 2 , :three = 3 ] see aList["one"] + nl + aList["two"] + nl + aList["three"] + nl # print 1 2 3 see aList[1] # print one 1 Tip: using : before identifier (one word) means literal Note: using = inside list definition create a list of two items where the first item is the left side and the second item is the right side. We can add new items to the list using the string index Example: aList = [] aList["Egypt"] = "Cairo" aList["KSA"] = "Riyadh" see aList["Egypt"] + nl + # print Cairo aList["KSA"] + nl # print Riyadh 26.17 Passing Parameters Using List This type of lists is very good for passing parameters to functions Where the order of parameters will not be important (we can change the order). Also some parameters maybe optional. Example: 26.16. Access List Items by String Index 193
- 10. Ring Documentation, Release 1.5.3 myconnect ( [ :server = "myserver.com" , :port = 80 , :username = "mahmoud" , :password = "password" ] ) func myconnect mypara # print connection details see "User Name : " + mypara[:username] + nl + "Password : " + mypara[:password] + nl + "Server : " + mypara[:server] + nl + "Port : " + mypara[:port] 26.18 Swap Items We can swap the list items using the Swap() function. Example: aList = [:one,:two,:four,:three] see aList see copy("*",50) + nl swap(aList,3,4) see aList Output one two four three ************************************************** one two three four 26.18. Swap Items 194