Lists

In this chapter we are going to learn how to deal with lists.

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

Add Items

To add new items to the list, we can use the Add() function.

Syntax:

Add(List,Item)

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

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

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

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

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

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

Reverse

We can reverse a list using the reverse() function.

Syntax:

Reverse(List) ---> Reversed List

Example:

aList = [10,20,30,40,50]
aList = reverse(aList)
see aList       # print 50 40 30 20 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

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

Copy Lists

We can copy lists (including nested lists) using the Assignment operator.

Example:

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

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]

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

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
        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]

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

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:

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]

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