exercism fetch haskell clock


Implement a clock that handles times without dates.

You should be able to add and subtract minutes to it.

Two clocks that represent the same time should be equal to each other.


To complete this exercise you need to define the data type Clock, with Eq, Show and Num instances, and implement the functions:

The function fromInteger, from Num, must convert minutes to 24 hour clock time. It is not necessary to have a sensible implementation of abs or signum.

You will find a dummy data declaration and type signatures already in place, but it is up to you to define the functions and create a meaningful data type, newtype or type synonym.

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:

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!


Pairing session with Erin Drummond https://twitter.com/ebdrummond

Submitting Incomplete Solutions

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