Difference between revisions of "PERL/C2/for-for-each-loops/English-timed"

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|-

|Welcome to the spoken tutorial on '''for '''and''' foreach Loops''' in '''Perl'''

|Welcome to the spoken tutorial on '''for '''and''' foreach Loops''' in '''Perl'''

   

   

|-

|-

| In this tutorial, we will learn about: '''for''' loop in '''Perl '''and

| In this tutorial, we will learn about: '''for''' loop in '''Perl '''and

|-

|-

|'''foreach''' loop in '''Perl'''

|'''foreach''' loop in '''Perl'''

   

   

|-

|-

| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''

| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''

   

   

|-

|-

|I will also be using the '''gedit '''Text Editor.

|I will also be using the '''gedit '''Text Editor.

   

   

|-

|-

|You can use any text editor of your choice.

|You can use any text editor of your choice.

   

   

|-

|-

| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''

| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''

   

   

|-

|-

|If not, please go through the relevant spoken tutorials on the '''spoken tutorial '''website.

|If not, please go through the relevant spoken tutorials on the '''spoken tutorial '''website.

   

   

|-

|-

|  '''Perl''' provides a mechanism by which we can check a condition repeatedly for various values. This is done using '''loops'''.

|  '''Perl''' provides a mechanism by which we can check a condition repeatedly for various values. This is done using '''loops'''.

   

   

|-

|-

|  There are various types of loops in Perl;

|  There are various types of loops in Perl;

   

   

|-

|-

|'''for loop'''

|'''for loop'''

   

   

|-

|-

|'''foreach loop'''

|'''foreach loop'''

   

   

|-

|-

|'''while loop &'''

|'''while loop &'''

   

   

|-

|-

|'''do-while loop'''

|'''do-while loop'''

|-

|-

|In this tutorial, we'll cover '''for''' and '''foreach loop'''.

|In this tutorial, we'll cover '''for''' and '''foreach loop'''.

   

   

|-

|-

| '''for '''loop in '''Perl''' can be used to execute a piece of code for a certain number of times.

| '''for '''loop in '''Perl''' can be used to execute a piece of code for a certain number of times.

   

   

|-

|-

| The syntax of '''for loop''' is as follows:

| The syntax of '''for loop''' is as follows:

|-

|-

|'''for space open bracket variable initialization semicolon condition semicolon increment

|'''for space open bracket variable initialization semicolon condition semicolon increment

|-

|-

|close bracket''' Press '''Enter'''

|close bracket''' Press '''Enter'''

|-

|-

|Open curly brackets

|Open curly brackets

   

   

|-

|-

|Piece of code to be executed multiple times

|Piece of code to be executed multiple times

|-

|-

|Close curly brackets

|Close curly brackets

   

   

|-

|-

| Now let us look at an example of a '''for '''loop.

| Now let us look at an example of a '''for '''loop.

   

   

|-

|-

| Open the '''Terminal''' and type; '''gedit forLoop.pl space & (ampersand)'''

| Open the '''Terminal''' and type; '''gedit forLoop.pl space & (ampersand)'''

   

   

|-

|-

|and press''' Enter'''

|and press''' Enter'''

   

   

|-

|-

|  This will open the '''forLoop.pl''' file in '''gedit'''.

|  This will open the '''forLoop.pl''' file in '''gedit'''.

   

   

|-

|-

| Type the following piece of code;'''hash exclamation mark slash u s r slash bin slash perl'''

| Type the following piece of code;'''hash exclamation mark slash u s r slash bin slash perl'''

   

   

|-

|-

|Press '''Enter'''

|Press '''Enter'''

   

   

|-

|-

|'''for space open bracket dollar i equals to zero semicolon space dollar i less than or equal to four semicolon space dollar i plus plus close bracket'''

|'''for space open bracket dollar i equals to zero semicolon space dollar i less than or equal to four semicolon space dollar i plus plus close bracket'''

   

   

|-

|-

|space

|space

   

   

|-

|-

|Open curly bracket  press enter

|Open curly bracket  press enter

   

   

|-

|-

| type'''print space double quote Value of i colon space dollar i slash n''' close double quote '''semicolon '''  

| type'''print space double quote Value of i colon space dollar i slash n''' close double quote '''semicolon '''  

   

   

|-

|-

| And Press '''Enter'''  

| And Press '''Enter'''  

   

   

|-

|-

|now close curly bracket

|now close curly bracket

   

   

|-

|-

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

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

   

   

|-

|-

| Let me explain what the '''for''' loop does.

| Let me explain what the '''for''' loop does.

|-

|-

|The variable '''i''' is initialized to zero.

|The variable '''i''' is initialized to zero.

   

   

|-

|-

|  Next, the condition is checked.  

|  Next, the condition is checked.  

   

   

|-

|-

|In this case, the condition is '''i less than or equal to 4'''.

|In this case, the condition is '''i less than or equal to 4'''.

   

   

|-

|-

|If this condition is true, the code within the curly bracket will be executed.

|If this condition is true, the code within the curly bracket will be executed.

   

   

|-

|-

|  This means the first '''print''' statement  '''"Value of i colon 0"'''

|  This means the first '''print''' statement  '''"Value of i colon 0"'''

   

   

|-

|-

|will be displayed on the '''terminal'''.

|will be displayed on the '''terminal'''.

   

   

|-

|-

| After this, the variable '''i''' is incremented by '''1.'''  

| After this, the variable '''i''' is incremented by '''1.'''  

   

   

|-

|-

| And the '''for''' loop condition is checked once again.

| And the '''for''' loop condition is checked once again.

   

   

|-

|-

|This loop will exit when the value of''' i''' becomes greater than '''4'''.

|This loop will exit when the value of''' i''' becomes greater than '''4'''.

   

   

|-

|-

| In this case, the '''for''' loop will be executed for '''i = 0, 1, 2, 3, 4'''

| In this case, the '''for''' loop will be executed for '''i = 0, 1, 2, 3, 4'''

|-

|-

|which is a total of '''5 '''times.

|which is a total of '''5 '''times.

   

   

|-

|-

|  Now, switch to  '''terminal'''.

|  Now, switch to  '''terminal'''.

   

   

|-

|-

| Type the following to check for any compilation or syntax error:

| Type the following to check for any compilation or syntax error:

   

   

|-

|-

|'''perl hyphen c forLoop dot pl'''

|'''perl hyphen c forLoop dot pl'''

   

   

|-

|-

|and press''' Enter.'''

|and press''' Enter.'''

   

   

|-

|-

|  Here it displays a message  

|  Here it displays a message  

   

   

|-

|-

|'''forLoop.pl syntax OK'''

|'''forLoop.pl syntax OK'''

   

   

|-

|-

|So, we have no errors.

|So, we have no errors.

   

   

|-

|-

| Now, let's execute the '''Perl''' script by typing '''perl forLoop dot pl''' and press '''Enter.'''

| Now, let's execute the '''Perl''' script by typing '''perl forLoop dot pl''' and press '''Enter.'''

   

   

|-

|-

|  The following output will be shown on terminal.

|  The following output will be shown on terminal.

   

   

|-

|-

| Now, let us look at  '''foreach '''loop.

| Now, let us look at  '''foreach '''loop.

   

   

|-

|-

| If we want to iterate a condition for an '''array''', we can make use of '''foreach '''loop.

| If we want to iterate a condition for an '''array''', we can make use of '''foreach '''loop.

   

   

|-

|-

|  The syntax is: '''foreach space dollar variable space within brackets at the rate array ''' space  

|  The syntax is: '''foreach space dollar variable space within brackets at the rate array ''' space  

|-

|-

|open curly bracket  

|open curly bracket  

   

   

|-

|-

|'''perform action on each element of an array ''' Press '''Enter'''

|'''perform action on each element of an array ''' Press '''Enter'''

   

   

|-

|-

|Close the curly bracket.

|Close the curly bracket.

   

   

|-

|-

|'''Please note: '''We'll cover array, array initialization and defining an array in subsequent tutorials.

|'''Please note: '''We'll cover array, array initialization and defining an array in subsequent tutorials.

   

   

|-

|-

|  Now let us look at an example of '''foreach''' loop.

|  Now let us look at an example of '''foreach''' loop.

   

   

|-

|-

|  Open the '''Terminal''' and type '''gedit foreachLoop dot pl space ampersand'''and Press''' Enter'''

|  Open the '''Terminal''' and type '''gedit foreachLoop dot pl space ampersand'''and Press''' Enter'''

   

   

|-

|-

|  This will open the '''foreachLoop.pl''' file in '''gedit'''.

|  This will open the '''foreachLoop.pl''' file in '''gedit'''.

   

   

|-

|-

| Type the following piece of code

| Type the following piece of code

|-

|-

|'''hash exclamation mark slash u s r slash bin slash perl''' and Press '''Enter'''

|'''hash exclamation mark slash u s r slash bin slash perl''' and Press '''Enter'''

   

   

|-

|-

|'''at the rate myarray space is equal to space open bracket ten comma twenty comma  thirty close bracket semicolon'''

|'''at the rate myarray space is equal to space open bracket ten comma twenty comma  thirty close bracket semicolon'''

   

   

|-

|-

|press enter  

|press enter  

   

   

|-

|-

|'''foreach space dollar var space open bracket at the rate myarray close bracket space'''

|'''foreach space dollar var space open bracket at the rate myarray close bracket space'''

|-

|-

|Open curly bracket  press enter and type

|Open curly bracket  press enter and type

   

   

|-

|-

|'''print space double quote Element of an array is colon dollar var  slash n'' close double quote  '''semicolon'''  

|'''print space double quote Element of an array is colon dollar var  slash n'' close double quote  '''semicolon'''  

|-

|-

|Press '''Enter''' and Close the curly bracket

|Press '''Enter''' and Close the curly bracket

   

   

|-

|-

|  Press '''ctrl+s''' to '''save''' the file.

|  Press '''ctrl+s''' to '''save''' the file.

   

   

|-

|-

| Let me explain what this code does. An array '''myarray '''is declared.  

| Let me explain what this code does. An array '''myarray '''is declared.  

   

   

|-

|-

|It has 3 elements 10, 20 and 30.

|It has 3 elements 10, 20 and 30.

   

   

|-

|-

|  In each iteration of foreach loop dollar var will contain the single element of an array

|  In each iteration of foreach loop dollar var will contain the single element of an array

   

   

|-

|-

|  '''foreach '''keyword will repeat this loop for each element of an array.

|  '''foreach '''keyword will repeat this loop for each element of an array.

   

   

|-

|-

|  That is, the code within the curly bracket will be executed for each '''myarray '''element.

|  That is, the code within the curly bracket will be executed for each '''myarray '''element.

   

   

|-

|-

| '''Back-slash n''' will place the prompt on a new line.

| '''Back-slash n''' will place the prompt on a new line.

   

   

|-

|-

| This means the first '''element''' ''''10'''' will be displayed on the terminal.

| This means the first '''element''' ''''10'''' will be displayed on the terminal.

|-

|-

|Then 20 and so on, till all the elements are printed.

|Then 20 and so on, till all the elements are printed.

   

   

|-

|-

|  This loop will exit after printing all the elements in '''myarray'''.

|  This loop will exit after printing all the elements in '''myarray'''.

   

   

|-

|-

| Now, switch to terminal and type the following to check for any compilation or syntax error.

| Now, switch to terminal and type the following to check for any compilation or syntax error.

   

   

|-

|-

|type '''perl hyphen c foreachLoop dot pl'''and press''' Enter.'''

|type '''perl hyphen c foreachLoop dot pl'''and press''' Enter.'''

   

   

|-

|-

|  The following line will be shown on terminal

|  The following line will be shown on terminal

   

   

|-

|-

|  There are no compilation or syntax errors.

|  There are no compilation or syntax errors.

   

   

|-

|-

|So let us execute the '''Perl''' script.

|So let us execute the '''Perl''' script.

|-

|-

|Type  '''perl foreachLoop dot pl''' and press '''Enter'''

|Type  '''perl foreachLoop dot pl''' and press '''Enter'''

   

   

|-

|-

|  The following output will be shown on terminal.

|  The following output will be shown on terminal.

|-

|-

| So, that's it about '''for''' loop and '''foreach''' loop.

| So, that's it about '''for''' loop and '''foreach''' loop.

   

   

|-

|-

|  Let us summarize.

|  Let us summarize.

   

   

|-

|-

|In this tutorial, we have learnt -

|In this tutorial, we have learnt -

   

   

|-

|-

|'''for''' loop and '''foreach''' loop in '''Perl'''

|'''for''' loop and '''foreach''' loop in '''Perl'''

   

   

|-

|-

|using some sample programs.

|using some sample programs.

 

 

|-

|-

|  Here is an assignment for you -

|  Here is an assignment for you -

   

   

|-

|-

| Declare a string as 'Spoken Tutorial' and  

| Declare a string as 'Spoken Tutorial' and  

|-

|-

| Print it 5 times

| Print it 5 times

|-

|-

| Declare an array of colors as @colorArray = open bracket in single quote red comma white comma  blue close the bracket and  

| Declare an array of colors as @colorArray = open bracket in single quote red comma white comma  blue close the bracket and  

|-

|-

| Print the element of an array using '''foreach''' loop

| Print the element of an array using '''foreach''' loop

   

   

|-

|-

|Watch the video available at the following link

|Watch the video available at the following link

   

   

|-

|-

|It summaries the Spoken Tutorial project

|It summaries the Spoken Tutorial project

   

   

|-

|-

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

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

   

   

|-

|-

|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials

|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials

   

   

|-

|-

|Gives certificates to those who pass an online  test

|Gives certificates to those who pass an online  test

|-

|-

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

|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

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

   

   

|-

|-

|It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|It is supported by the National Mission on Education through ICT, MHRD, Government of India.

   

   

|-

|-

|More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro

|More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro

   

   

|-

|-

|  Hope you enjoyed this Perl tutorial.  

|  Hope you enjoyed this Perl tutorial.  

   

   

|-

|-

|This is Amol signing off.

|This is Amol signing off.

|-

|-

|Thanks for joining.

|Thanks for joining.

   

   

|}

|}