polysemy VS eff

Compare polysemy vs eff and see what are their differences.


:gemini: higher-order, no-boilerplate monads (by polysemy-research)


🚧 a work in progress effect system for Haskell 🚧 (by hasura)
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polysemy eff
6 16
982 523
0.6% 1.7%
4.5 0.8
about 2 months ago over 2 years ago
Haskell Haskell
BSD 3-clause "New" or "Revised" License ISC License
The number of mentions indicates the total number of mentions that we've tracked plus the number of user suggested alternatives.
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.


Posts with mentions or reviews of polysemy. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2022-04-19.


Posts with mentions or reviews of eff. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2023-03-12.
  • [ANNOUNCE] GHC 9.6.1 is now available
    2 projects | reddit.com/r/haskell | 12 Mar 2023
    There are also a few subtle issues that arise with delconts related to semantics of higher order effects (see here and here), but they might be solvable.
  • Effectful | Paweł Szulc | Lambda Days 2022
    3 projects | reddit.com/r/haskell | 13 Dec 2022
    Details are in https://github.com/hasura/eff/issues/12 and https://www.reddit.com/r/haskell/comments/pywuqg/unresolved_challenges_of_scoped_effects_and_what/.
  • Looking for languages that combine algebraic effects with parallel execution
    4 projects | reddit.com/r/ProgrammingLanguages | 25 Oct 2022
    You'll get fearless parallel with STM in the mixture, and GHC is getting a work in progress effect system for Haskell, as Delimited continuation primops has been merged.
  • Should I pick up OCaml or Haskell?
    3 projects | reddit.com/r/functionalprogramming | 24 Aug 2022
    My last example is algebraic effects, some of which have been made possible in a both practical and efficient way thanks to extremely recent research, and that I can use to implement architectures like Ports and Adapters or Clean Architecture and have very maintainable code. (Extensible Effects — An Alternative to Monad Transformers was published in 2013, Effect Handlers in Scope was published in 2014 and they are behind Polysemy, while there is ongoing work on effects with even better performance, like Eff)
  • [ANN] cleff - fast and consise extensible effects
    2 projects | reddit.com/r/haskell | 30 Jan 2022
    cleff's Eff monad is esentially implemented as a ReaderT IO. [...] This is first done by eff, [...]
  • Opinions on Reader + Continuation-based IO?
    3 projects | reddit.com/r/haskell | 1 Dec 2021
    Here is link number 1 - Previous text "eff"
    3 projects | reddit.com/r/haskell | 1 Dec 2021
    This is essentially how continuation based effect systems work, check out eveff and eff.
  • Where's more discussion of the designs of effect systems?
    4 projects | reddit.com/r/ProgrammingLanguages | 17 Nov 2021
    Languages such as Koka only support algebraic effects, not scoping operations such as catch and listen. The Effect Handlers in Scope paper introduces scoping operations, which lead to the Haskell libraries fused-effects and polysemy, but they turned out to have some weird semantics. eff is her effort to fix that.
    4 projects | reddit.com/r/ProgrammingLanguages | 17 Nov 2021
    While her eff is still under construction, there are relative more mature pieces like Koka etc. I'd very much like to understand how her concerns map to those other effect systems, but can't find more write-ups about the design space of effect systems.
  • The Problem of Effects (2020)
    5 projects | news.ycombinator.com | 27 Aug 2021
    Let me tell you what I'm worried about with effects systems: One of the smartest people I know of has a library called Eff https://github.com/hasura/eff that efficiently implements effects through some modifications to GHC. The thing is, she's pretty much stopped working on because she found some really nasty semantic edge-cases that she couldn't resolve to her satisfaction. (I don't understand the problems well enough to describe them, and I think they're specific to lazy languages, but it has left me cautious about the effect model in general.)

What are some alternatives?

When comparing polysemy and eff you can also consider the following projects:

fused-effects - A fast, flexible, fused effect system for Haskell

purescript - A strongly-typed language that compiles to JavaScript

Exercism - Scala Exercises - Crowd-sourced code mentorship. Practice having thoughtful conversations about code.

freer-simple - A friendly effect system for Haskell

ast-monad - A library for constructing AST by using do-notation

ghc - Mirror of the Glasgow Haskell Compiler. Please submit issues and patches to GHC's Gitlab instance (https://gitlab.haskell.org/ghc/ghc). First time contributors are encouraged to get started with the newcomers info (https://gitlab.haskell.org/ghc/ghc/wikis/contributing).

haskell.nix - Alternative Haskell Infrastructure for Nixpkgs

frp-zoo - Comparing many FRP implementations by reimplementing the same toy app in each.

linear - Low-dimensional linear algebra primitives for Haskell.

extensible-effects - Extensible Effects: An Alternative to Monad Transformers