Solved–Homework Assignment #2– Solution

1

• Text Transformation[15pts]

Suppose you are given a text file ‘q2.in‘, a piece of text (a sequence of lines). A sample text looks like this:

O Captain! my Captain! our fearful trip is done,

The ship has weather’d every rack, the prize we sought is won,

Assume that the words are separated by spaces.

Part 1. Write a subroutine to swap str1 with str2 in ‘q2.in‘. Your program should use standard input(keyboard input) and print results to a file named ‘q2p1.out‘. Input contains two lines, first line is str1, second line is str2. All strings and words are case senstive.

sample input:

Captain

shirley

sample ‘q2p1.out‘:

O shirley! my shirley! our fearful trip is done.

The ship has weather’d every rack, the prize we sought is won,

———

Explanation:

str1 is “Captain”, str2 is “shirley”.

your code should be able to change all “Captain” into “shirley”.

Part 2. Write a subroutine to remove lines that has exact K(K 1) words in ‘q2.in‘. If there are no such lines, print out “Oooh Nooo!”. Your program should use standard input(keyboard input) and print results to a file named ‘q2p2.out‘. Input only has one line containing integer K.

sample input:

9

sample q2p2.out:

The ship has weather’d every rack, the prize we sought is won,

——

Explanation:

The first line has 9 words:

O shirley! my shirley! our fearful trip is done.

sample input:

2

sample q2p2.out:

Oooh Nooo!

——

Explanation:

Both lines in q2.in have more than 2 words.

• Array Operators and Hashes [20 pts]

Part 1. Write a program that takes a text file as input(as a command line argument). This file contains a set of words in each line and a feature(an integer) associated with this set of words, separated by a comma. The feature varies from 0 to 9, inclusive.

Please print out the total number of words with a particular feature value. The output should be in the following format:

• perl q3_p1.pl features.txt total_#_of_words_with_0 total_#_of_words_with_1 total_#_of_words_with_2

..

..

total_#_of_words_with_9

Part 2.

The following table has the revenue(in dollars) of a small company for each month in the year 2017:

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Revenue ($)	4840	4340	3900	4330	3090	3660	3520	3280	4130	3690	4260	4800

You should write a program that calculates the cumulative revenue of two months given by the user. The three letter month abbreviations are not case sensitive. The program must use a hash of revenue and be able to handle invalid input, otherwise keep asking for the months. Please, read carefully the explanation of the sample inputs and outputs for further details. [10 pts]

$ perl q3_p2.pl

Enter the initial month: Feb

Enter the final month: may

The cumulative revenue is: 15660

————

Explanation:

The cumulative revenue depends on “Feb”, “Mar”, “Apr” and “May”.

$ perl q3_p2.pl

Months can be selected using the three initials letters.

Enter the initial month: apr

Enter the final month: July

Please enter only the three initials letters of a valid month.

Re-enter the final month: uly

Please enter only the three initials letters of a valid month.

Re-enter the final month: jUL

The cumulative revenue is: 14600

————

Explanation:

The program keeps asking for the correct final month initials.

Then, it shows the cumulative revenue that depends on “Apr”, “May”, “Jun” and “July”.

$ perl q3_p2.pl

Months can be selected using the three initials letters.

Enter the initial month: june

Please enter only the three initials letters of a valid month.

Re-enter the initial month: jun

Enter the final month: feb

Please enter only the three initials letters of a valid month.

Re-enter the final month: jul

The cumulative revenue is: 7180

————

Explanation:

The program keeps asking for the correct initial month initials.

“Feb” can not be the final month given “Jun” as the initial month.

Then, it shows the cumulative revenue that depends on “Jun” and “Jul”.

4

• Files and Directories [20 pts]

In this question, you are asked to split the feature values from question 3 part1 into 10 different files as follows:

1. Create a directory named “features”.

2. Inside “features” directory, create 10 files with the following format: “N-features.txt”, where “N” is an integer from 0 to 9.

3. From the file “features.txt”, read each line and add it (without the feature value) to the corresponding “N-features.txt” file. For example, the file “3-features.txt” will only contain the lines with a feature value of 3.

4. Once done, your program should print “Files have been created!” and in the next 10 lines print the full path of each file.

$ perl q4.pl features.txt Files have been created!

“print full path of 0-features.txt here” “print full path of 1-features.txt here” “print full path of 2-features.txt here”

..

..

..

“print full path of 9-features.txt here”

Please do not create any file or folder manually and do not attach any of the created files in this question.

Your program will be tested on a different dataset.

• Regular Expressions [25 pts]

In this question, each subsection contains different types of regular expression questions.

5.1 Matching strings[4 pts each]

For each item below, write a regular expression that matches the strings on the left, while not matching the strings on the right. Note: The regular expression should match entire strings, not just the beginning/end of it.

	be or not to be					to be or
	to be to be					to be
	to be to be to be					to be or not
	to be to be to be to be					to be or not to
	hello		cat.
	world!!		dog?
	hello!?		computer..
	perl?!		world!

For submission, create a text file named “q5_p1.txt”, and provide your regular expression solution for each item in a new line(i.e., 2 lines in total).

5.2 More Regular Expression Questions[4 pts each]

Write a regular expression that matches the following format: Month/day/year(For example: “1/25/2018”, “3/11/2119”, “6/8/224”, but not “6/54/1996”). The regular expression you wrote should capture month, day and year information as separate groups. To keep things simple, you can assume there are 30 days in every month, and the year field has at most 4 digits.

Write a regular expression that matches a sentence in which every word has less than 5 characters. Note: The last word cannot be followed by a space.

For submission, create a text file named “q5_p2.txt”, and provide your regular expression solution for each section in a new line.

5.3 Finding examples and counter-examples[3 pts each]

For the regular expressions presented below, provide three strings that matches the regular expression, and three strings that do not match the regular expression.

[-+]?\d*(\.\D+)?F\s (#?)(1?)(one)\1\2\3 ((a*?)\b).*\w\2\1

For submission, create a text file named “q5_p3.txt”, and provide your examples by indicating whether it matches or not. This part will not be graded by a script, so you are allowed to use whichever format you want, as long as you make your answers clear.