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Question 2: Encoding Cryptography is the study of trying to create secure information by obscuring the original message. One simple encryption method is to substitute letters from the original message with other letters. To make it harder to decrypt the hidden message, we may also remove clues such as the length of the words in the message and any punctuation or capitalization. Write a function encode that consumes a string message. The function produces a string which is encrypted according the following procedure: • Only the letters from the original message will be encrypted. Other characters such as spaces, punctuation, numeric digits, etc. are not included in the encrypted message at all. • The encrypted message will only contain uppercase letters. • Each letter will be replaced by the uppercase letter at the opposite end of the English alphabet. In other words, A or a will become z, B or b will become Y, C or c will become x, .., z or z will become A. • The encrypted message will have a single space separating each letter. You may assume that the letters in message are English letters only. For example: > (encode "Cat") 2 "X Z G" |> (encode "A")| 1 4 " > (encode "Is this correct?") 6 "R H G SRH XLII V X G" Additional Restrictions • For this question you are only allowed to define one named function: encode. You may define local constants. There will be severe correctness mark penalties for solutions that include any named helper functions. • You may use lambda expressions in your solution within the application of other functions. However remember that an expression like this: (define function (lambda ...)) is defining a named function. Any lambda expressions in your solution should only appear as part of some expression that includes (lambda ...) but produces a value that is not a function. • Do not solve the problem of encrypting letters by using a cond which has 26 (or more) question/answer pairs - one for each letter of the alphabet.

Question 2: Encoding Cryptography is the study of trying to create secure information by obscuring the original message. One simple encryption method is to substitute letters from the original message with other letters. To make it harder to decrypt the hidden message, we may also remove clues such as the length of the words in the message and any punctuation or capitalization. Write a function encode that consumes a string message. The function produces a string which is encrypted according the following procedure: • Only the letters from the original message will be encrypted. Other characters such as spaces, punctuation, numeric digits, etc. are not included in the encrypted message at all. • The encrypted message will only contain uppercase letters. • Each letter will be replaced by the uppercase letter at the opposite end of the English alphabet. In other words, A or a will become z, B or b will become Y, C or c will become x, .., z or z will become A. • The encrypted message will have a single space separating each letter. You may assume that the letters in message are English letters only. For example: > (encode "Cat") 2 "X Z G" |> (encode "A")| 1 4 " > (encode "Is this correct?") 6 "R H G SRH XLII V X G" Additional Restrictions • For this question you are only allowed to define one named function: encode. You may define local constants. There will be severe correctness mark penalties for solutions that include any named helper functions. • You may use lambda expressions in your solution within the application of other functions. However remember that an expression like this: (define function (lambda ...)) is defining a named function. Any lambda expressions in your solution should only appear as part of some expression that includes (lambda ...) but produces a value that is not a function. • Do not solve the problem of encrypting letters by using a cond which has 26 (or more) question/answer pairs - one for each letter of the alphabet.

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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Question 2: Encoding Cryptography is the study of trying to create secure information by obscuring the original message. One simple encryption method is to substitute letters from the original message with other letters. To make it harder to decrypt the hidden message, we may also remove clues such as the length of the words in the message and any punctuation or capitalization. Write a function encode that consumes a string message. The function produces a string which is encrypted according the following procedure: • Only the letters from the original message will be encrypted. Other characters such as spaces, punctuation, numeric digits, etc. are not included in the encrypted message at all. • The encrypted message will only contain uppercase letters. • Each letter will be replaced by the uppercase letter at the opposite end of the English alphabet. In other words, A or a will become z, B or b will become Y, C or c will become x, .., z or z will become A. • The encrypted message will have a single space separating each letter. You may assume that the letters in message are English letters only. For example: > (encode "Cat") 2 "X Z G" |> (encode "A")| 1 4 " > (encode "Is this correct?") 6 "R H G SRH XLII V X G" Additional Restrictions • For this question you are only allowed to define one named function: encode. You may define local constants. There will be severe correctness mark penalties for solutions that include any named helper functions. • You may use lambda expressions in your solution within the application of other functions. However remember that an expression like this: (define function (lambda ...)) is defining a named function. Any lambda expressions in your solution should only appear as part of some expression that includes (lambda ...) but produces a value that is not a function. • Do not solve the problem of encrypting letters by using a cond which has 26 (or more) question/answer pairs - one for each letter of the alphabet.
Transcribed Image Text:Question 2: Encoding Cryptography is the study of trying to create secure information by obscuring the original message. One simple encryption method is to substitute letters from the original message with other letters. To make it harder to decrypt the hidden message, we may also remove clues such as the length of the words in the message and any punctuation or capitalization. Write a function encode that consumes a string message. The function produces a string which is encrypted according the following procedure: • Only the letters from the original message will be encrypted. Other characters such as spaces, punctuation, numeric digits, etc. are not included in the encrypted message at all. • The encrypted message will only contain uppercase letters. • Each letter will be replaced by the uppercase letter at the opposite end of the English alphabet. In other words, A or a will become z, B or b will become Y, C or c will become x, .., z or z will become A. • The encrypted message will have a single space separating each letter. You may assume that the letters in message are English letters only. For example: > (encode "Cat") 2 "X Z G" |> (encode "A")| 1 4 " > (encode "Is this correct?") 6 "R H G SRH XLII V X G" Additional Restrictions • For this question you are only allowed to define one named function: encode. You may define local constants. There will be severe correctness mark penalties for solutions that include any named helper functions. • You may use lambda expressions in your solution within the application of other functions. However remember that an expression like this: (define function (lambda ...)) is defining a named function. Any lambda expressions in your solution should only appear as part of some expression that includes (lambda ...) but produces a value that is not a function. • Do not solve the problem of encrypting letters by using a cond which has 26 (or more) question/answer pairs - one for each letter of the alphabet.
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