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Roc has algebraic effects instead of Monads for effect tracking. The two systems are exactly as expressive as each other [1]. Algebraic effects compose better t

Roc has algebraic effects instead of Monads for effect tracking. The two systems are exactly as expressive as each other [1]. Algebraic effects compose better than Monads, and are probably more beginner friendly. Imo Monadic code can be a little easier to follow sometimes since there’s less non-local control flow. They are both great things to have in a language and I’m super excited to see how much progress Roc is making in both approachability and performance when it comes to pure functional programming. [1]: https://homepages.inf.ed.ac.uk/slindley/papers/effmondel-jfp.pdf https://homepages.inf.ed.ac.uk/slindley/papers/effmondel-jfp...

rtfeldman 2y ago
Roc actually doesn't use algebraic effects under the hood, although errors can naturally accumulate in a way that makes the code look more like error handling in algebraic effects systems: https://www.roc-lang.org/tutorial#task-failure https://www.roc-lang.org/tutorial#task-failure The implementation detail that makes this error handling possible is that Roc uses anonymous sum types called "tags" (OCaml calls them polymorphic variants) that can accumulate on the fly: https://www.roc-lang.org/tutorial#tags https://www.roc-lang.org/tutorial#tags
- tkz1312 2y ago
  Very interesting, thanks for the clarification. What is the difference between algebraic effects and rocs approach?
  - rtfeldman 2y ago
    In Haskell terms, Roc's `Task ok err` is essentially an `IO (Either err ok)` - the only difference between how Roc does it and how Haskell does it is that `Task` bakes in error handling whereas `IO` doesn't. (Plus the syntax sugar being different, of course.) So the biggest difference is that algebraic effects are a separate language feature, whereas Task (like IO in Haskell) is a plain old type in the standard library that happens to represent effeects. Incidentally, the Task.await function in Roc is based on Elm's Task.andThen - we just tried out a different name and argument order for it: https://package.elm-lang.org/packages/elm/core/latest/Task#andThen https://package.elm-lang.org/packages/elm/core/latest/Task#a...
bedobi 2y ago
can someone explain in plain English and with some easy to understand code examples?
ngruhn 2y ago
But do algebraic effects preserve referential transparency? It’s hard for me to see that they do.

rtfeldman 2y ago

Roc actually doesn't use algebraic effects under the hood, although errors can naturally accumulate in a way that makes the code look more like error handling in algebraic effects systems: https://www.roc-lang.org/tutorial#task-failure https://www.roc-lang.org/tutorial#task-failure The implementation detail that makes this error handling possible is that Roc uses anonymous sum types called "tags" (OCaml calls them polymorphic variants) that can accumulate on the fly: https://www.roc-lang.org/tutorial#tags https://www.roc-lang.org/tutorial#tags

tkz1312 2y ago
Very interesting, thanks for the clarification. What is the difference between algebraic effects and rocs approach?
- rtfeldman 2y ago
  In Haskell terms, Roc's `Task ok err` is essentially an `IO (Either err ok)` - the only difference between how Roc does it and how Haskell does it is that `Task` bakes in error handling whereas `IO` doesn't. (Plus the syntax sugar being different, of course.) So the biggest difference is that algebraic effects are a separate language feature, whereas Task (like IO in Haskell) is a plain old type in the standard library that happens to represent effeects. Incidentally, the Task.await function in Roc is based on Elm's Task.andThen - we just tried out a different name and argument order for it: https://package.elm-lang.org/packages/elm/core/latest/Task#andThen https://package.elm-lang.org/packages/elm/core/latest/Task#a...

bedobi 2y ago

can someone explain in plain English and with some easy to understand code examples?

ngruhn 2y ago

But do algebraic effects preserve referential transparency? It’s hard for me to see that they do.