Forth in Haskell
Implement an evaluator for a very simple subset of Forth
exercism fetch haskell forth
Implement an evaluator for a very simple subset of Forth.
Forth is a stack-based programming language. Implement a very basic evaluator for a small subset of Forth.
Your evaluator has to support the following words:
Your evaluator also has to support defining new words using the
: word-name definition ;.
To keep things simple the only data type you need to support is signed integers of at least 16 bits size.
You should use the following rules for the syntax: a number is a sequence of one or more (ASCII) digits, a word is a sequence of one or more letters, digits, symbols or punctuation that is not a number. (Forth probably uses slightly different rules, but this is close enough.)
Words are case-insensitive.
To complete this exercise, you need to create the data type
and implement the following functions:
emptyreturns an empty
evalTextevaluates an input Text, returning the new state.
toListreturns the current stack as a list, with the element on top of the stack being the rightmost (last) element.
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.
For installation and learning resources, refer to the exercism help page.
Running the tests
To run the test suite, execute the following command:
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:
If you want to play with your solution in GHCi, just run the command:
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!
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.