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Hareactive is a higher-order high-performance fully featured FRP library. Hareactive aims to be practical, powerful and simple.


Hareactive is highly inspired by the papers Push-Pull Functional Reactive Programming by Conal Elliott and Practical principled FPP by Atze van der Ploeg and Koen Claessen.

Hareactive implements classic FRP. This means that it makes a distinction between behaviors and event (event is called stream in Hareactive though). As for why that distinction is useful see the blogpost Behaviors and streams, why both?.

Behaviors in Hareactive are monads. Monadic behaviors are essential for many practical purposes. Behaviors in Hareactive can be continous, i.e. change infinetly often. Among other things this means that Hareactive support continous time and integration.

Hareactive supports stateful behaviors (i.e. behaviors that depends on the past). It does so while avoiding the problems with space and time leaks that FRP are notorius for.

A key focus is to implement a simple precise semantic model following the principles of Conal Elliott. The semantics serve as a specification for determining the correctness of the implementation. Additionally, it is a mental model which can be used to reason about the library.

Hareactive is implemented in carefully optimized TypeScript.


npm i @funkia/hareactive
bower install --save purescript-hareactive


Module documentation is published on Pursuit.