FRP - Release of reactive-banana version 0.5
I have released version 0.5.0.0 of my reactive-banana library on hackage.
For this release, I have introduced many changes to the public API and completely rewritten the internals. However, the core FRP model and semantics are merely extended, not changed, so it should be straightforward to port existing code to the new version.
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The most profound API change is that the types Event,
Behavior and NetworkDescription now carry an
phantom type parameter t, as discussed in a previous
blog post.
Simultaneous event occurrences have long been a point of trouble.
With the rewritten internals, I was now able to add combinators like
calm or unionWith that allow you to observe
and handle simultaneity. This is particularly useful for dealing with
incremental updates. Furthermore, I have removed the general
Monoid instance for Event to discourage the
accidental introduction of simultaneous occurrences. Taking it even
further, I have added an experimental module
Reactive.Banana.Experimental.Calm that exports a variant
semantics where simultaneous occurrences are simply forbidden.
Another noteworthy change is that the Behavior type now
partially exposes a notion of “changes”, similar to the old
Discrete type, which I have removed again. Suggested by
Elliott Hird, this change greatly simplifies your reactive-banana
experience as it restores the prominence of the Behavior
type. While Behavior is still to be thought of as
continuously varying value, the glue code that communicates with GUI
frameworks can now observe changes, but only inside the
NetworkDescription monad sin-bin. I think that this is a
good compromise between elegant semantics and efficient
implementation.
Many thanks to all users for suggesting and discussing changes with me, especially Elliott Hird, Gregory Crosswhite and Henning Thielemann.