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

|'''Time'''

|'''Narration'''

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| In this tutorial, we will learn about:

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|'''Index''' of an array  

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|Length of an array  

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|Accessing elements of an array  

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|Looping over an array  

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| '''Sequential Array''' and

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|'''Array Slicing'''.

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

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

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

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

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

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

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

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| The syntax for declaring an array is: 

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

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

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|Open the terminal and type:

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

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

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

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

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

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

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

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

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|The output will be as displayed on the terminal.

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

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

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

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

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

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

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| Switch to the terminal and type: 

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

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|press '''Enter.'''

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

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

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

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

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

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| Now, let us execute the script.  

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|  Switch to terminal and type:

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|Indexing is used to access elements of an array.  

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

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|First Position, Last Position  

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|Any position.

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| Switch to the terminal and type:

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

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

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

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

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|zero is passed as index.

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

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

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| Switch to the terminal and execute the  script as:

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| The output will be as shown on the terminal.

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

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

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|Using '''for''' loop

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|Using '''foreach''' loop.

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|For this, switch to the terminal and type:  

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|and press '''Enter'''.

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

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

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

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

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| Once the array reaches its last element, it will exit the ''' foreach''' loop.  

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|06:58

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

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

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

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

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

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

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|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.

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

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

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

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

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

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|Find '''index''' of an array  

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|'''Access''' elements of an array  

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|'''Loop''' over an array  

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|'''Sequential Array''' and

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

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|Here is an assignment for you: 

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| Declare an array of rainbow colors.

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| Print 4th element of this array.

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| Print Length and last index of this array.

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

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| 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'''.  

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|Watch the video available at the following link.

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|It summaries the Spoken Tutorial project.

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

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

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| Gives certificates to those who pass an online test.

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

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

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

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

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|This is Amol, signing off.

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