Difference between revisions of "PERL/C2/Hash-in-Perl/English-timed"

|Welcome to the spoken tutorial on ''' Hash''' in '''Perl'''.

| In this tutorial, we will learn about;

|'''Hash''' in '''Perl''' and  

| Accessing element of a '''hash'''  

|For this tutorial, I am using  

| ''' Ubuntu Linux12.04''' operating system  

|''' Perl 5.14.2''' and  

| ''' gedit''' Text Editor  

|To practise this tutorial, you should have knowledge of ''' Variables & Data Structures''' in '''Perl.'''

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

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

|''' Hash''' is an unordered collection of data   

|It's a ''' key/value pair data structure '''

| '''Hash keys''' are unique  

|However, ''' Hash''' can have duplicate values  

| This is the declaration of a ''' hash''' .  

|Let us see how to get the value of a ''' key''' from '''hash. '''

|The syntax for accessing the value of a ''' key''' is  

|''' dollar hashName open curly bracket single quote keyName single quote close curly bracket'''

|I have already typed the code in ''' perlHash dot pl''' file in '''gedit. '''

| ''' Hash''' in ''' Perl''' is declared with '''percentage''' sign.  

| These are the keys of '''hash.'''

|And these are the values of '''hash.'''   

|Note: To access ''' key''' of '''hash''', one has to use '''dollar''' sign.  

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

|Then switch to ''' terminal''' and execute the '''Perl script''' as  

|''' perl perlHash dot pl'''

|and press ''' Enter'''.

|Now let us see add and delete of ''' keys''' from  '''hash.'''  

|The syntax for .

|adding key is ''' dollar hashName open curly bracket '''

|''' single quote KeyName single quote'''  

|''' close curly bracket equal to $value semicolon'''  

|deleting key is ''' delete dollar hashName open curly bracket'''  

|'''single quote KeyName single quote close curly bracket semicolon'''  

| This is the declaration of ''' hash.'''

|We'll be adding, deleting the ''' keys''' from this ''' hash.'''

|It is like assigning a value to a variable.  

|''' delete''' keyword is used to delete the ''' key.'''  

| 03:31

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

|Switch to the terminal and execute the ''' Perl script''' as  

| 03:40

|   03:44

|  and press ''' Enter.'''

| Let us look at ''' sorting''' of a ''' hash keys''' and '''values.'''

| Syntax to ''' sort keys''' is  

|''' sort open bracket keys percentage hashName close bracket semicolon '''

|Similarly, we can '''sort hash values''' as  

|''' sort open bracket values percentage hashName close bracket semicolon'''  

|Let us understand ''' sorting''' functionality using a sample program.   

|Let me switch to ''' sortHash dot pl'''  on ''' gedit.'''

|Type the code as displayed on the screen in your ''' sortHash dot pl''' file.  

| Here we have declared ''' hash''' of '''address. '''

|Here, to sort the ''' keys''' we have used the '''sort''' inbuilt function, along with the '''keys''' function.  

|Sorting can also be done on ''' numeric keys''' and/or '''values.'''

|Save the file and switch to terminal.  

|Execute the script by typing ''' perl sortHash dot pl''' and Press ''' Enter '''

|Now, let us see how to get all ''' keys ''' and ''' values''' of '''hash.'''

|''' Perl''' provides inbuilt ''' function''' to fetch all the ''' hash keys''' and ''' values.'''  

|''' keys function''' is used to retrive all the ''' keys''' of ''' hash '''

| ''' values''' function returns ''' values''' of all the ''' keys''' whereas  

| ''' each''' function iterates over ''' hash''' and returns ''' key/value''' pair from ''' hash'''  

| Let us understand these using a sample program.  

| For this, we'll use '''perlHash dot pl''' script, which we have created earlier in this tutorial.  

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

|''' keys''' function on ''' hash''', returns an '''array''' which contains all '''keys''' of '''hash.'''

| ''' values''' function on ''' hash''' returns an '''array''' of '''values''' for all '''keys''' of '''hash'''.

| ''' each'''  function returns the ''' key/value''' pair.  

|Here, we have used the ''' while loop.'''

|It will iterate over each ''' key/value''' pair of ''' hash,''' that is returned by '''each function'''.

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

| ''' perl perlHash dot pl'''  

| And Press ''' Enter'''

|Now let us see few other ways of looping over ''' hash.'''

| We can use ''' foreach loop''' to iterate over each '''key''' of '''hash'''.  

|Then perform a set of actions on the value of a key.

| Here, each iteration of ''' foreach loop''' will assign '''key''' from ''' hash''' to ''' $variable.'''

|Then it will use that ''' $variable''' to fetch the  value or to perform a set of actions.  

|So, let me switch to ''' loopingOverHash dot pl''' in '''gedit.'''

| Type the following piece of code as shown in your ''' loopingOverHash dot pl'''  

|This piece of code returns single ''' key''' of '''hash.'''

|Here in our case,  

|1st time ''' dollar key ($key)''' contains the ''' Department''' as ''' key.'''  

|In the next iteration of '''foreach, Name key''' is returned.  

|Note: ''' Hash''' is an unordered collection of data.  

|So, ''' keys''' returned will not be in the sequence defined at the time of creating '''hash.'''

| The loop on ''' values''' works in a similar way.  

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

|Then, switch to terminal and execute the ''' Perl script''' as  

|and press ''' Enter.'''

|Let us summarize.  

 

|In this tutorial, we learnt -

|''' Hash''' in '''Perl''' and  

|Accessing elements of a '''hash'''  

|Here is assignment for you -

|And '''his/her percentage''' as the '''value'''.  

|Loop over '''hash''' using '''keys, values''' and '''each''' function  

|Then print the ''' percentage''' of each student.  

|Watch the video available at the following link

|It summaries the Spoken Tutorial project

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| Hope you enjoyed this Perl tutorial.  

|This is Amol signing off.