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jim108dev's solution

to Scrabble Score in the Haskell Track

Published at Mar 27 2021 · 0 comments
Instructions
Test suite
Solution

Given a word, compute the Scrabble score for that word.

Letter Values

You'll need these:

Letter                           Value
A, E, I, O, U, L, N, R, S, T       1
D, G                               2
B, C, M, P                         3
F, H, V, W, Y                      4
K                                  5
J, X                               8
Q, Z                               10

Examples

"cabbage" should be scored as worth 14 points:

  • 3 points for C
  • 1 point for A, twice
  • 3 points for B, twice
  • 2 points for G
  • 1 point for E

And to total:

  • 3 + 2*1 + 2*3 + 2 + 1
  • = 3 + 2 + 6 + 3
  • = 5 + 9
  • = 14

Extensions

  • You can play a double or a triple letter.
  • You can play a double or a triple word.

Getting Started

Please refer to the installation and learning help pages.

Running the tests

To run the test suite, execute the following command:

stack test

If you get an error message like this...

No .cabal file found in directory

You are probably running an old stack version and need to upgrade it.

Otherwise, if you get an error message like this...

No compiler found, expected minor version match with...
Try running "stack setup" to install the correct GHC...

Just do as it says and it will download and install the correct compiler version:

stack setup

Running GHCi

If you want to play with your solution in GHCi, just run the command:

stack ghci

Feedback, Issues, Pull Requests

The exercism/haskell repository on GitHub is the home for all of the Haskell exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!

Source

Inspired by the Extreme Startup game https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

Tests.hs

{-# OPTIONS_GHC -fno-warn-type-defaults #-}
{-# LANGUAGE RecordWildCards #-}

import Data.Foldable     (for_)
import Test.Hspec        (Spec, describe, it, shouldBe)
import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)

import Scrabble (scoreLetter, scoreWord)

main :: IO ()
main = hspecWith defaultConfig {configFastFail = True} specs

specs :: Spec
specs = do
          describe "scoreLetter" $ do
            it "'a'" $ scoreLetter 'a' `shouldBe`  1
            it "'Z'" $ scoreLetter 'Z' `shouldBe` 10
            it "'?'" $ scoreLetter '?' `shouldBe`  0
          describe "scoreWord" $ for_ cases test
  where

    test Case{..} = it description assertion
      where
        assertion = scoreWord input `shouldBe` fromIntegral expected

data Case = Case { description :: String
                 , input       :: String
                 , expected    :: Integer
                 }

cases :: [Case]
cases = [ Case { description = "lowercase letter"
               , input       = "a"
               , expected    = 1
               }
        , Case { description = "uppercase letter"
               , input       = "A"
               , expected    = 1
               }
        , Case { description = "valuable letter"
               , input       = "f"
               , expected    = 4
               }
        , Case { description = "short word"
               , input       = "at"
               , expected    = 2
               }
        , Case { description = "short, valuable word"
               , input       = "zoo"
               , expected    = 12
               }
        , Case { description = "medium word"
               , input       = "street"
               , expected    = 6
               }
        , Case { description = "medium, valuable word"
               , input       = "quirky"
               , expected    = 22
               }
        , Case { description = "long, mixed-case word"
               , input       = "OxyphenButazone"
               , expected    = 41
               }
        , Case { description = "english-like word"
               , input       = "pinata"
               , expected    = 8
               }
        , Case { description = "empty input"
               , input       = ""
               , expected    = 0
               }
        , Case { description = "entire alphabet available"
               , input       = "abcdefghijklmnopqrstuvwxyz"
               , expected    = 87
               }
        ]

-- a0aa908486542f98a0e421ed775f18945317506e
module Scrabble
  ( scoreLetter
  , scoreWord
  ) where

import           Data.Map                       ( Map )
import qualified Data.Map                      as Map
import           Data.Char                      ( toUpper )

letters2Value :: Map String Integer
letters2Value = Map.fromList
  [ ("AEIOULNRST", 1)
  , ("DG"        , 2)
  , ("BCMP"      , 3)
  , ("FHVWY"     , 4)
  , ("K"         , 5)
  , ("JX"        , 8)
  , ("QZ"        , 10)
  ]

scoreLetter :: Char -> Integer
scoreLetter letter = Map.foldr (+) 0
  $ Map.filterWithKey (\k _ -> toUpper letter `elem` k) letters2Value

scoreWord :: String -> Integer
scoreWord word = sum (scoreLetter <$> word)

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?