We present a user-friendly approach to unifying program creation and execution, based on a notion of “tangible values” (TVs), which are visual and interactive manifestations of pure values, including functions. Programming happens by gestural composition of TVs. Our goal is to give end-users the ability to create parameterized, composable content without imposing the usual abstract and linguistic working style of programmers. We hope that such a system will put the essence of programming into the hands of many more people, and in particular people with artistic/visual creative style.
In realizing this vision, we develop algebras for visual presentation and for “deep” function application, where function and argument may both be nested within a structure of tuples, functions, etc. Composition gestures are translated into chains of combinators that act simultaneously on statically typed values and their visualizations.
See also the video Tangible Functional Programming: a modern marriage of usability and composability.
Here are two figures from the paper, showing stages of an interactively composed interactive 2D region. The user selects compatibly-typed input and output widgets, typically in different TVs. The result is a new TV that merges the source TVs, except for the connected input and output, which vanish. The sliders control the disk and checker sizes and the checker's rotation angle.
@InProceedings{Elliott2007:Eros,
author = {Conal Elliott},
title = {Tangible Functional Programming},
url = {http://conal.net/papers/Eros/},
booktitle = "International Conference on Functional Programming",
year = 2007
}