Applicative bots
In Functional reactive partner dancing, I mentioned that (a) the partially applied leading and following types have boilerplate Applicative instances, and (b) the leading type corresponds to varying (reactive) values. Today I realized that those boilerplate instances are not very useful, and that they do not correspond to the Applicative instance of Reactive. In this post, I give a useful Applicative instance that does correspond to the Reactive instance. The instance definition is expressed in terms of the pair editor bot shown at the end of the “dancing” post, which seems to have a variety of applications.
The Applicative instance has one awkward aspect that suggests a tweak to the formulation of leading. I give simplified versions of pair editing and Applicative for the revised type. This change is in version 0.1 of the Bot libary.
Edit 2008-02-15: added FRP tags; prose tweak.