An experiment exploring a UI programming model inspired by algebraic effects.

An algebraic effect system such as Oleg Kiselyov’s presentation might model individual effects as the combination of a functor and a handler function which performs the actions represented in the datatype. In like fashion, the current work represents each aspect of UI programming—layouts, drawings, interactions, etc.—as a functor with an associated function to perform its actions.

Where we start to diverge is to think of these functors as being languages instead of effects, and of their corresponding functions as interpreters instead of handlers.

To be precise, each language is an embedded DSL. Each functor has associated “smart” constructors which wrap a single, nonrecursive value up into a recursive structure, and the result is an idiomatic Haskell API presenting the facilities offered by the language in question.