Data.UI

The UI library provides a more modern getLine style function for making console based CLIs (command line interfaces). The library provides editing capabilities through the use of arrow keys, as well as browsing through the command history.

It is very minimalistic, does only export two functions and doesn't require its own monad (only IO).

Data types

data Term

Term is the internal state of the library.

Constructors

Term

Fields

• initialized :: Bool
• log :: Vector Line
• logpos :: Int
• loglen :: Int
• buf :: Line
• len :: Int
• pos :: Int
• prompt :: Line

Instances

Show Term

Defined in Data.UI

Methods

showsPrec :: Int -> Term -> ShowS

show :: Term -> String

showList :: [Term] -> ShowS

data TermRes

TermRes is the result of the input. Returned whenever the user presses a key.

Constructors

TKey Key

Returns the numeric value on each key press (except enter).

TLine Line

Returns the line of data when user presses enter.

Instances

Show TermRes

Defined in Data.UI

Methods

showsPrec :: Int -> TermRes -> ShowS

show :: TermRes -> String

showList :: [TermRes] -> ShowS

type Line = String

Line is the datatype of the returned text string when the user presses enter. This type can easily be changed from the default (String) to Text or anything else. Change it in the type alias and it will be used everywhere.

Functions

init :: Line -> IO Term

init initial_prompt

Initializes the terminal. Returns a handle which you pass on to the input function.

input :: Term -> IO (TermRes, Term)

input handle

Reads one character from the keyboard. You give it the handle from the last function call. It returns the string when pressed enter and returns the key code otherwise.

Example:

> 
> import qualified Data.UI (init, input)
> import Data.UI (TermRes(..))
> 
> example :: IO ()
> example = do
>     t <- Data.UI.init "prompt> "
>     go t
>     where
>      go t' = do
>         (res,newstate) <- Data.UI.input t'
>         case res of
>             TLine x  -> do
>                          _ <- putStrLn $ "\nResult: '" <> x <> "'"
>                          go newstate
>             _        -> go newstate
>