PropLang

A design for a GUI library which is more like Haskell and less like C.

Link: http://www.cse.unsw.edu.au/~chak/haskell/ports/

Thoughts by

Neil Mitchell

The Var concept

This is the low level stuff, on which the library will be built

data Var a = ...
data Notify

get :: Var a -> IO a
set :: Var a -> a -> IO ()
addNotify :: Var a -> IO () -> IO Notify
remNotify :: Notify -> IO ()

newVar :: a -> IO (Var a)

Object layering

textBox-text -< "test"
filename <- newVar Nothing
addNotify filename hatCover
lbl-text =< with filename $ \x ->
                 case x of
                     Nothing -> "Select a file"
                     Just x -> "Loaded: " ++ x

where

(-) :: GtkObject -> GtkProp -> Var a -- ignoring lots of details here
(-<) :: Var a -> a -> IO ()
(=<) :: Var a -> Action a -> IO ()

with :: Var a -> (a -> b) -> Action b