How to resolve the algorithm 99 bottles of beer step by step in the Haskell programming language

Published on 7 June 2024 03:52 AM
#Haskell

How to resolve the algorithm 99 bottles of beer step by step in the Haskell programming language

Table of Contents

Problem Statement

Display the complete lyrics for the song:     99 Bottles of Beer on the Wall.

The lyrics follow this form: ... and so on, until reaching   0     (zero). Grammatical support for   1 bottle of beer   is optional. As with any puzzle, try to do it in as creative/concise/comical a way as possible (simple, obvious solutions allowed, too).

Let's start with the solution:

Step by Step solution about How to resolve the algorithm 99 bottles of beer step by step in the Haskell programming language

First example:

This code snippet is written in Haskell and it implements the "99 bottles of beer" song. It starts by defining the main function which is the entry point of the program. The main function calls the mapM_ function which applies the beer function to each element of the list [99, 98 .. 0] and then prints the result. The beer function takes a number as input and returns a string representing the corresponding verse of the song. If the number is 1, the function returns the first verse of the song, if the number is 0, the function returns the last verse of the song, otherwise the function returns the verse for the given number.

Second example:

This code snippet is a Haskell implementation of the "99 bottles of beer" song using Template Haskell. The code starts by defining the main function which is the entry point of the program. The main function calls the putStr function which prints the value of the songString variable. The songString variable is defined using Template Haskell and it contains the lyrics of the song. The song variable is defined by calling the execWriter function with the mapM_ function which applies the verse function to each element of the list [99,98..1]. The verse function takes a number as input and returns a string representing the corresponding verse of the song.

Third example:

This code snippet is a Haskell implementation of the "99 bottles of beer" song using point-free style. The code starts by defining the main function which is the entry point of the program. The main function calls the putStrLn function which prints the value of the expression unlines (mapM_ incantation [99, 98 .. 0]). The incantation function takes a number as input and returns a string representing the corresponding verse of the song. The inventory function takes a number as input and returns a string representing the number of bottles of beer. The asset function takes a number as input and returns a string representing the number of bottles of beer. The location variable is a string representing the location of the bottles of beer. The distribution variable is a string representing the distribution of the bottles of beer. The solution variable is a string representing the solution to the song.

Source code in the haskell programming language

main = mapM_ (putStrLn . beer) [99, 98 .. 0]
beer 1 = "1 bottle of beer on the wall\n1 bottle of beer\nTake one down, pass it around"
beer 0 = "better go to the store and buy some more."
beer v = show v ++ " bottles of beer on the wall\n" 
                ++ show v 
                ++" bottles of beer\nTake one down, pass it around\n" 
                ++ head (lines $ beer $ v-1) ++ "\n"


import qualified Char

main = putStr $ concat
   [up (bob n) ++ wall ++ ", " ++ bob n ++ ".\n" ++
    pass n ++ bob (n - 1) ++ wall ++ ".\n\n" |
    n <- [99, 98 .. 0]]
   where bob n = (num n) ++ " bottle" ++ (s n) ++ " of beer"
         wall = " on the wall"
         pass 0 = "Go to the store and buy some more, "
         pass _ = "Take one down and pass it around, "
         up (x : xs) = Char.toUpper x : xs
         num (-1) = "99"
         num 0    = "no more"
         num n    = show n
         s 1 = ""
         s _ = "s"


{-# LANGUAGE TemplateHaskell #-}
-- build with "ghc --make beer.hs"
module Main where
import Language.Haskell.TH
import Control.Monad.Writer

-- This is calculated at compile time, and is equivalent to
-- songString = "99 bottles of beer on the wall\n99 bottles..."
songString = 
    $(let
         sing = tell -- we can't sing very well...

         someBottles 1 = "1 bottle of beer "
         someBottles n = show n ++ " bottles of beer "

         bottlesOfBeer n = (someBottles n ++) 

         verse n = do
           sing $ n `bottlesOfBeer` "on the wall\n"
           sing $ n `bottlesOfBeer` "\n"
           sing $ "Take one down, pass it around\n"
           sing $ (n - 1) `bottlesOfBeer` "on the wall\n\n"

         song = execWriter $ mapM_ verse [99,98..1]

      in return $ LitE $ StringL $ song)

main = putStr songString


location, distribution, solution :: String
[location, distribution, solution] =
  [ "on the wall",
    "Take one down, pass it around",
    "Better go to the store to buy some more"
  ]

incantation :: Int -> String
incantation n
  | 0 == n = solution
  | otherwise =
    unlines
      [ inventory n,
        asset n,
        distribution,
        inventory $ pred n
      ]

inventory :: Int -> String
inventory = unwords . (: [location]) . asset

asset :: Int -> String
asset n =
  let suffix n
        | 1 == n = []
        | otherwise = ['s']
   in unwords
        [show n, (reverse . concat) $ suffix n : ["elttob"]]

main :: IO ()
main = putStrLn $ unlines (incantation <$> [99, 98 .. 0])

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