"Tangible Functional Programming" — icfp version

Paper draft: "Applicative Data-Driven Computation"

I would love to get comments on a short (4.5 page) paper draft called “Applicative Data-Driven Computation” (Haskell wiki page), which describes a very simple approach to data-driven (push-based) computation and its application to GUI programming. There’s a “Talk page” link for discussion.

I’m also very interested in suggestions and (better yet) collaboration on other applications of data-driven computation beyond GUIs, say push-based internet apps.

Software releases: TypeCompose, Phooey, GuiTV

Three related software releases. I am very interested in comments and contributions.

TypeCompose provides some classes & instances for forms of type composition. It also includes a very simple implementation of data-driven computation. I factored it out of a new implementation of Phooey. Phooey is a library for functional user interfaces. Highlights in this 0.3 release:

  • Uses new TypeCompose package, which includes a simple implementation of data-driven computation.
  • New Applicative functor interface.
  • Eliminated the catch-all Phooey.hs module. Now import any one of Graphics.UI.Phooey.{Monad ,Applicative,Arrow}.
  • Phooey.Monad has two different styles of output widgets, made by owidget and owidget’. The latter is used to implement Phooey.Applicative.
  • Self- and mutually-recursive widgets now work again in Phooey.Monad. They wedge in Phooey.Arrow and Phooey.Applicative.

Phooey is also used in GuiTV, a library for composable interfaces and “tangible values”. I’ve also just updated GuiTV to 0.3, to sync with Phooey 1.0.

Software releases

Last week I released three Haskell libraries: DeepArrow 0.0, Phooey 0.1, and TV 0.0.

These libraries came from Eros, which aims at creating a right-brain-friendly (concrete, non-linguistic) “programming” process. I’ve had a growing intuition over the last fifteen years that media authoring tools can be usefully looked at as environments for functional programming. I’d been wondering how to map a user’s gestures into operations on a functional program. Lots of noodling led to ideas of composable interfaces and “tangible values” (term thanks to Sean Seefried) and gestural composition in Eros.

Eros is more complicated than I like, so I started splitting it into pieces:

  • Phooey is a functional GUI library that has much of Eros’s GUI implementation techniques, but much more carefully structured than in the Eros paper.
  • DeepArrow has the general notion of “deep application”
  • TV has the algebra of composable interfaces, or visualizations of pure values, and it has tangible values, which are separable combinations of interface and value. It uses Phooey to generate GUIs very simply from interfaces

Although these libraries came from Eros, I’d like to see other applications as well.

Where am I going with library development?

  • Figure out how to support simple GUIs and Eros’s gesturally composable GUIs, without code/library replication.
  • Re-implement Eros on top of simpler pieces.
  • Refactor Pajama into reusable libraries and release.
    • Building and optimizing “expressions”
    • Common sub-expression elimination
    • Generation of Java code
    • Perhaps other back-ends besides Java
    • Pajama, on top of these pieces

Edit of March 5, 2007: TV is now split into a core TV package, with no GUI functionality, and GuiTV, with Phooey-based GUI creation. The reason for the split is that Phooey depends on wxHaskell, which can be difficult to install.