BASH/C3/Recursive-function/English-timed

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Time Narration
00:01 Dear friends, welcome to the spoken tutorial on Recursive function.
00:07 In this tutorial, we will learn
00:10 What is a Recursive function
00:12 with the help of some examples.
00:15 To follow this tutorial, you should have knowledge of Shell Scripting in BASH.
00:20 If not, for relevant tutorials, please visit our website which is as shown.http://www.spoken-tutorial.org
00:27 For this tutorial, I am using
00:29 Ubuntu Linux 12.04 Operating System
00:33 and GNU BASH version 4.2
00:37 Please note, GNU Bash version 4 or above is recommended for practice.
00:44 Let us see what a recursive function is.
00:48 A recursive function is one which calls itself.
00:52 Recursion is a useful technique for simplifying complex algorithms.
00:59 Let me open a file named factorial.sh.
01:04 I have typed the code in this file.
01:07 This is the shebang line.
01:10 factorial is the function name.
01:12 Inside this, we print a message “Inside factorial function”.
01:19 This statement reads user's input and stores the value in variable 'n'.
01:26 Here, we have if-else condition.
01:30 If condition checks whether the value of 'n' is equal to zero.
01:36 If True, it will display the message "factorial value of n is 1".
01:42 Here is the else part of the if statement.
01:46 It calls the factorial function.
01:50 And fi is the end of the if-else statement.
01:55 Let us run the file factorial.sh.
01:59 Open the terminal using CTRL+ALT+T keys simultaneously on your keyboard.
02:07 Type: chmod space plus x space factorial dot sh
02:15 Press Enter.
02:17 Type dot slash factorial.sh
02:21 Press Enter.
02:24 We see "Enter the number".
02:26 I will enter 0.
02:29 The output is displayed as:
02:31 factorial value of 0 is 1
02:35 Now press the up-arrow key. Recall the previous command.
02:40 Press Enter.
02:42 This time, I will enter 5 .
02:45 Now the output is displayed as:
02:47 Inside factorial function.
02:51 Let us add some more logic to the factorial function.
02:56 We will calculate the factorial of a number.
03:01 Come back to our code.
03:03 Now let us replace the echo statement inside the factorial function with the code block.
03:10 Click on Save.
03:13 temp is a variable and stores the value entered by user.
03:19 If condition checks whether the variable value is equal to 1.
03:25 If True, it will print 1.
03:29 This is the else part of the if statement.
03:33 This reduces one from the temp variable value
03:37 and stores the result in a variable 'f'.
03:42 Variable f stores the output of factorial function.
03:46 This is a recursive call.
03:50 Value of variable f and temp is multiplied and stored in f.
03:57 Then we print the value of f.
04:00 End of if-else statement and function.
04:05 Now come back to our slides.
04:08 Let us understand the flow of the program.
04:12 # The value of n is taken from the user i.e. n.
04:17 # If the value entered is equal to zero then it prints a message
04:24 # Else it goes to the function factorial.
04:29 # Here, if the value is 'equal to one' then it prints value as 'one'.
04:36 # If not, it makes a recursive call until the value is equal to one.
04:44 # Then, all the values are multiplied and displayed.
04:49 Now come back to our terminal.
04:52 Press the up-arrow key.
04:54 Recall the previous command ./factorial.sh
04:58 Press Enter.
05:00 Now I will enter 5 as the input value.
05:05 We get the factorial of number 5
05:08 that is 120.
05:11 We can see the flow of the program on terminal. Analyze and trace the flow of the program.
05:18 Come back to our slides.
05:20 Let us summarize.
05:21 In this tutorial, we have learned
05:23 Recursive function
05:25 with the help of some examples.
05:28 As an assignment,
05:29 write a program where the recursive function calculates the sum of N numbers.
05:36 Watch the video available at the link shown below.
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06:10 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
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06:24 The script has been contributed by FOSSEE and Spoken-Tutorial teams.
06:29 This is Ashwini Patil. signing off.
06:33 Thank you for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14