# Commander CLI

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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 the task-manager application which comes with this
repository. The library is based around the following classes:

```haskell
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

```haskell
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.