We are going to do the Transform
step of an Extract-Transform-Load.
Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so we're going to migrate this."
(Typically, this is followed by, "We're only going to need to run this once." That's then typically followed by much forehead slapping and moaning about how stupid we could possibly be.)
We're going to extract some Scrabble scores from a legacy system.
The old system stored a list of letters per score:
- 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
- 2 points: "D", "G",
- 3 points: "B", "C", "M", "P",
- 4 points: "F", "H", "V", "W", "Y",
- 5 points: "K",
- 8 points: "J", "X",
- 10 points: "Q", "Z",
The shiny new Scrabble system instead stores the score per letter, which makes it much faster and easier to calculate the score for a word. It also stores the letters in lower-case regardless of the case of the input letters:
- "a" is worth 1 point.
- "b" is worth 3 points.
- "c" is worth 3 points.
- "d" is worth 2 points.
- Etc.
Your mission, should you choose to accept it, is to transform the legacy data format to the shiny new format.
A final note about scoring, Scrabble is played around the world in a variety of languages, each with its own unique scoring table. For example, an "E" is scored at 2 in the Māori-language version of the game while being scored at 4 in the Hawaiian-language version.
This exercise works with textual data. For historical reasons, Haskell's
String
type is synonymous with [Char]
, a list of characters. For more
efficient handling of textual data, the Text
type can be used.
As an optional extension to this exercise, you can
-
Read about string types in Haskell.
-
Add
- text
to your list of dependencies in package.yaml. -
Import
Data.Text
in the following way:import qualified Data.Text as T import Data.Text (Text)
-
You can now write e.g.
transform :: Map Int Text -> Map Char Int
and refer toData.Text
combinators as e.g.T.toLower
. -
Look up the documentation for
Data.Text
.
This part is entirely optional.
Please refer to the installation and learning help pages.
To run the test suite, execute the following command:
stack test
No .cabal file found in directory
You are probably running an old stack version and need to upgrade it.
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
If you want to play with your solution in GHCi, just run the command:
stack ghci
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!
The Jumpstart Lab team http://jumpstartlab.com
It's possible to submit an incomplete solution so you can see how others have completed the exercise.