1 exercism fetch haskell bowling

# Bowling

Score a bowling game.

Bowling is a game where players roll a heavy ball to knock down pins arranged in a triangle. Write code to keep track of the score of a game of bowling.

## Scoring Bowling

The game consists of 10 frames. A frame is composed of one or two ball throws with 10 pins standing at frame initialization. There are three cases for the tabulation of a frame.

• An open frame is where a score of less than 10 is recorded for the frame. In this case the score for the frame is the number of pins knocked down.

• A spare is where all ten pins are knocked down by the second throw. The total value of a spare is 10 plus the number of pins knocked down in their next throw.

• A strike is where all ten pins are knocked down by the first throw. The total value of a strike is 10 plus the number of pins knocked down in the next two throws. If a strike is immediately followed by a second strike, then the value of the first strike cannot be determined until the ball is thrown one more time.

Here is a three frame example:

Frame 1 Frame 2 Frame 3
X (strike) 5/ (spare) 9 0 (open frame)

Frame 1 is (10 + 5 + 5) = 20

Frame 2 is (5 + 5 + 9) = 19

Frame 3 is (9 + 0) = 9

This means the current running total is 48.

The tenth frame in the game is a special case. If someone throws a strike or a spare then they get a fill ball. Fill balls exist to calculate the total of the 10th frame. Scoring a strike or spare on the fill ball does not give the player more fill balls. The total value of the 10th frame is the total number of pins knocked down.

For a tenth frame of X1/ (strike and a spare), the total value is 20.

For a tenth frame of XXX (three strikes), the total value is 30.

## Requirements

Write code to keep track of the score of a game of bowling. It should support two operations:

• roll(pins : int) is called each time the player rolls a ball. The argument is the number of pins knocked down.
• score() : int is called only at the very end of the game. It returns the total score for that game.

## Hints

To complete this exercise you need to implement the function score, that takes a sequence of bowling rolls and returns the final score or the appropriate error:

 1 2 3 4 5 score :: [Int] -> Either BowlingError Int data BowlingError = IncompleteGame | InvalidRoll { rollIndex :: Int, rollValue :: Int } deriving (Eq, Show)

You will find these definitions already in place, but it is up to you to define the function.

Keep in mind that the test suite expects the rolls to be numbered starting from zero.

## Getting Started

For installation and learning resources, refer to the exercism help page.

## Running the tests

To run the test suite, execute the following command:

 1 stack test

#### If you get an error message like this...

 1 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...

 1 2 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:

 1 stack setup

## Running GHCi

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

 1 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

The Bowling Game Kata at but UncleBob http://butunclebob.com/ArticleS.UncleBob.TheBowlingGameKata

## Submitting Incomplete Solutions

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