Commander CLI

This library is meant to allow Haskell programs to quickly and easily construct command line interfaces which are easy to use, especially as a Haskell user. To begin, I suggest viewing/playing with the task-manager application which comes with this repository. Its usage info is generated as:

usage:
task-manager help
task-manager (required env: TASK_DIRECTORY :: [Char]> edit <task-name :: [Char]>
task-manager (required env: TASK_DIRECTORY :: [Char]> open <task-name :: [Char]>
task-manager (required env: TASK_DIRECTORY :: [Char]> close <task-name :: [Char]>
task-manager (required env: TASK_DIRECTORY :: [Char]> tasks
task-manager (required env: TASK_DIRECTORY :: [Char]> priorities
task-manager (required env: TASK_DIRECTORY :: [Char]>

The library is based around the following classes:

class Unrender r where
  unrender :: Text -> Maybe r

This class is what you will use to define the parsing of a type from text and can use any parsing library or whatever you want. Next, we have the class

class HasProgram p where
  data ProgramT p m a
  run :: ProgramT p IO a -> CommanderT State IO a
  hoist :: (forall x. m x -> n x) -> ProgramT p m a -> ProgramT p n a
  invocations :: [Text]

Instances of this class will define a syntactic element, a new instance of the data family ProgramT, as well as its semantics in terms of the CommanderT monad, which is a backtracking monad based on a metaphor to military commanders which retreats upon defeat.