Difference between revisions of "PERL/C2/Arrays/English-timed"

| In this tutorial, we will learn about:

|'''Index''' of an array  

|Length of an array  

|Accessing elements of an array  

|Looping over an array  

| '''Sequential Array''' and

|'''Array Slicing'''.

|Here, I am using ''' Ubuntu Linux 12.04''' operating system and '''Perl 5.14.2'''.

|You should have basic knowledge of ''' variables, comments & data Structures''' in '''Perl'''.

|Knowledge of '''loops''' and '''conditional statements''' will be an added advantage.

|Please go through the relevant spoken tutorials on the '''Spoken Tutorial''' website.  

|Array is a simple '''data structure''' which contains '''elements''' of any data type.   

| In '''Perl''', it is not necessary to declare the length of an array.   

|Array length expands/shrinks as and when elements are added/removed from it.  

| The syntax for declaring an array is: 

|'''@myArray equal to open bracket 1 comma  2 comma 3 comma  single quote abc single quote  comma 10.3''' close  bracket semicolon.

|The last index of an array can be found with this command: 

|Open the terminal and type:

| This will open '''arrayIndex dot pl''' file in '''geditor'''.

|Type the piece of code that is displayed on screen.  

|Here, we have declared & defined an array which contains 5 elements.  

|As '''array index''' starts from zero, the last index value will be 4  

|i.e number of elements which is 5, minus 1.  

|Press '''Ctrl+S''' to '''save''' the file.  

|Now, switch to  terminal and execute the Perl script.

| Type: ''' perl arrayIndex dot pl '''

|The output will be as displayed on the terminal.

|Now, let us see how to get length of an array in '''Perl'''.  

|There are many ways by which we can find the length of an array-

| Index of an array + 1  i.e. '''$#array + 1'''.

|Using PERL inbuilt scalar function; i.e.  '''scalar open bracket @array close bracket.'''  

|Assign array to a scalar variable i.e. '''$arrayLength = @array '''.

|03:09

| Let us look at an illustration of an array length using a sample program.   

|03:14

| Switch to the terminal and type: 

|03:18

| '''gedit arrayLength dot pl space ampersand ''' and

|press '''Enter.'''

|  Type the following piece of code as shown on the screen.

|Here, we have declared & defined an array which contains 5 elements.  

|Highlighted are the various ways to find the length of an array in '''Perl'''.  

| Please note: We have '''concatenated''' the output in the '''print''' statement using comma.  

|Press '''Ctrl + S''' to '''save''' the file.  

| Now, let us execute the script.  

|  Switch to terminal and type:

|Indexing is used to access elements of an array.  

|Let us look at an example for accessing elements of an array at: 

|First Position, Last Position  

|Any position.

| Switch to the terminal and type:

|Please note: '''myArray''' is declared with '''@''' (at the rate) sign.  

|But, to access an array element we need to use '''$'''(dollar) sign.  

|To access the element at any position, we need to pass '''index''' to an array.

|Here, to access the first element of '''myArray''',  

|zero is passed as index.

|To access the last element of '''myArray''' , we have passed the last index of '''myArray.'''

| Press '''Ctrl + S''' to '''save''' the file.  

| Switch to the terminal and execute the  script as:

| The output will be as shown on the terminal.

| Now, let us understand how to '''loop''' over each element of an array.

|There are two ways of '''looping over''' an array:

|Using '''for''' loop

|Using '''foreach''' loop.

|For this, switch to the terminal and type:  

|and press '''Enter'''.

| Type the piece of code as shown on the screen.

| Here, we are printing each element of array by iterating the index.  

| The '''for''' loop will execute till the value of 'i' variable reaches the last '''index''' of an array.  

|Here, '''foreach''' loop will be executed for each element of an array.

|please go through the relevant spoken tutorials on "spoken tutorial" website.  

| Now, press '''Ctrl + S''' to '''save''' the file.  

|Then switch to the terminal and execute the script as:

| In '''Perl''', we can declare a '''sequential array''' as:

|'''@alphaArray = open bracket a dot dot d close bracket semicolon'''  

|i.e '''alphaArray''' will contain elements 'a', 'b', 'c' and 'd'.

|Similarly, '''@numericArray ''' equal to open bracket 1 dot dot 5 close bracket semicolon  is same as '''@numericArray'''  equal to open bracket 1 comma  2 comma 3 comma 4 comma 5.

|'''Perl''' also provides '''array slicing'''.  

|'''@array = 19  comma 23 comma 56 comma 45 comma 87 comma 89''' close bracket semicolon  

| '''@newArray''' = '''@array''' open square bracket 1 comma 4 close square bracket semicolon  

|After '''slicing''', the  '''newArray''' will look like:

|Let us summarize. In this tutorial, we have learnt to:

|Find '''index''' of an array  

|'''Access''' elements of an array  

|'''Loop''' over an array  

|'''Sequential Array''' and

|'''Array Slicing''', using sample programs.  

|Here is an assignment for you: 

| Declare an array of rainbow colors.

| Print 4th element of this array.

| Print Length and last index of this array.

| Loop over each element of an array using '''for''' & '''foreach''' loops.

| Declare array as '''@myArray = open bracket 1..9 close bracket semicolon'''. And then create an array of odd numbers, from above array, using '''array slicing'''.  

|Watch the video available at the following link.

|It summaries the Spoken Tutorial project.

|If you do not have good bandwidth, you can download and watch it.

|  The Spoken Tutorial project team: * Conducts workshops using spoken tutorials.

| Gives certificates to those who pass an online test.

|For more details, please write to: contact at spoken hyphen tutorial dot org.

|  "Spoken Tutorial" project is a part of the "Talk to a Teacher" project.

|More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.

| Hope you enjoyed this '''Perl''' tutorial.  

|This is Amol, signing off.