eff has never been released to Hackage and as far as I know never used in production. I wouldn't call it "real-world code". For effect systems that people do ac

eff has never been released to Hackage and as far as I know never used in production. I wouldn't call it "real-world code". For effect systems that people do actually use in production I suggest * Polysemy: https://hackage.haskell.org/package/polysemy https://hackage.haskell.org/package/polysemy * effectful: https://hackage.haskell.org/package/effectful https://hackage.haskell.org/package/effectful * Bluefin: https://hackage-content.haskell.org/package/bluefin/docs/Bluefin.html https://hackage-content.haskell.org/package/bluefin/docs/Blu... [Disclosure: Bluefin in my effect system]