USE SCHEME LANGUAGE (R5RS) TO SOLVE THIS PROBLEM

1. Using Scheme higher-order function map to implement the string encryption and decrption. [10 points]

1.1 The encryption function must (1) take the encryption key (key can be between 1 and 4) from the keyboard using (read); and (2) encrypt alphabetic characters and digits only. [5]

1.2 The decryption function must (1) take the encryption key from the keyboard using (read) and (2) decrypt the string generated from your encryption function. [5]

Test cases:

(encrypt "Hello CSE240!")

(decrypt "Khoor FVH573!")

3

"Khoor FVH573!"

3

"Hello CSE240!"

Note: When you encrypt a valid character (letters and digits), you add a key to the character. When you decrypt, you will have a different set of the valid characters, which is caused by +key. You can limit the allowed key value to be 1, 2, 3, and 4.