[SOLVED] Functional-Programming Assignment 5-Monads

Assignment 5 Monads

5.1 Submission instructions

1. Unzip the A5.zip folder. It should contain one file: 􏰀 Solutions.hs – for the Haskell exercises
2. Edit the first line of each of the source files as described in the comments.
3. Edit the source files with your solutions.
4. When done, zip (not rar renamed as zip!) this A5 folder and name the zip archive with the following format:

   A5 ⟨FirstName⟩ ⟨LastName⟩ ⟨Group⟩

   Examples of valid names:

   􏰀 A5 John Doe 30432.zip
   􏰀 A5 Ion Popescu 30434.zip
   􏰀 A5 Gigel-Dorel Petrescu 30431.zip

   Examples of invalid names:

   􏰀 Solutions.zip
   􏰀 A5.zip
   􏰀 Solutii A5 Ion Popescu.zip

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5.2 Assignment exercises 5.2.1 Haskell

Exercise 5.2.1 3p

Implement a function passwords that enumerates all 8 character passwords containing digits (0 – 9) lowercase letters (a – z) and uppercase letters (A – Z) using the list applicative.

Haskell REPL

      > take 5 passwords
      ["00000000","00000001","00000002","00000003","00000004"]
      > take 5 (drop 10000 passwords)
      ["000002Bi","000002Bj","000002Bk","000002Bl","000002Bm"]

Hints:
Re-read section 10.2 of Lab 10 about the list applicative.
You should consider using (some of) the following functions: replicate , sequenceA .

Exercise 5.2.2 3p

Given the following data definition data Password = Password String , implement a func- tion validatePassword :: String -> Maybe Password that takes a string and returns a valid password wrapped in Just or Nothing , if the string isn’t a valid password.
A valid password should have at least 8 characters and should contain:

􏰀 At least one lowercase character 􏰀 At least one uppercase character 􏰀 At least one digit

> validatePassword "123"
Nothing
> validatePassword "abc"
Nothing

> validatePassword "MyStr0ngPassword2"
Just (Password "MyStr0ngPassword2")
> validatePassword "abcDE12"
Nothing

> validatePassword "Abcd1234"
Just (Password "Abcd1234")

Haskell REPL

Hints:
You should consider using (some of) the following functions: any , all , elem , notElem

Exercise 5.2.3 5p

Given the following data definition data Email = Email {username :: String, domain:: String} , write a function validateEmail :: String -> Maybe Email that takes a string a returns a valid email address wrapped in Just or Nothing , if the string isn’t a valid email ad- dress.

A valid email address ([email protected]) should: 146

• 􏰀  Contain a username (the part before the “@” character) that is at least 3 characters long (johnny)
• 􏰀  Contain exactly one “@” character
• 􏰀  Contain a domain name (the part after the “@” character) that contains:

  – A non-empty hostname (which can contain “.” characters) (example) – A “.” character
  – A top level domain (com)

  Haskell REPL

     > validateEmail "[email protected]"
     Just (Email {username = "johnny", domain = "example.com"})
     > validateEmail "[email protected]"
     Nothing
     > validateEmail "johnny.com"
     Nothing
     > validateEmail "johnny@[email protected]"
     Nothing
     > validateEmail "[email protected]"
     Nothing
     validateEmail "[email protected]"
     Just (Email {username = "johnny.john", domain = "domain.com"})
     > validateEmail "[email protected]"
     Just (Email {username = "johnny.john", domain = "domain.example.com"})
  

  Hints:
  You should consider using (some of) the following functions: span , break , null

  Exercise 5.2.4 4p

  Complete the main function in Solutions.hs to create a Haskell program for checking whether an email and password are valid. The program should prompt the user to enter their email address and password, check if they are a valid email address and password and show a message whether the input was valid or not.

  Grading:

  • 􏰀  2 points for implementing the validateUser :: String -> String -> Maybe User function that uses validateEmail and validatePassword to validate an email ad- dress and a password
  • 􏰀  2 points for implementing the main function

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