BSD-3-Clause licensed by Patai Gergely
Maintained by Patai Gergely ([email protected])
This version can be pinned in stack with:elerea-2.9.0@sha256:383f5b2d6639b529f4e12cf31e6076103832ef456e66dda167d1c3c2b3285abd,2242

Module documentation for 2.9.0

Elerea (Eventless reactivity) is a tiny discrete time FRP implementation without the notion of event-based switching and sampling, with first-class signals (time-varying values). Reactivity is provided through various higher-order constructs that also allow the user to work with arbitrary time-varying structures containing live signals. Signals have precise and simple denotational semantics.

Stateful signals can be safely generated at any time through a monadic interface, while stateless combinators can be used in a purely applicative style. Elerea signals can be defined recursively, and external input is trivial to attach. The library comes in two major variants:

  • Simple: signals are plain discrete streams isomorphic to functions over natural numbers;

  • Param: adds a globally accessible input signal for convenience;

This is a minimal library that defines only some basic primitives, and you are advised to install elerea-examples as well to get an idea how to build non-trivial systems with it. The examples are separated in order to minimise the dependencies of the core library. The dow package contains a full game built on top of the simple variant.

The basic idea of the implementation is described in the WFLP 2010 paper Efficient and Compositional Higher-Order Streams (

Additional contributions: Takano Akio, Mitsutoshi Aoe