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Since OCaml allows side-effects, they are not really necessary to do simple things like printing some output. The standard library is not monadic in nature. H

Since OCaml allows side-effects, they are not really necessary to do simple things like printing some output. The standard library is not monadic in nature. However, there are a some very popular monadic libraries (for example, for concurrency you have lwt and async). The main advantage is that you have explicit information over which calls are blocking (it's in the signature), and explicit control over when you relinquish control back to the coroutine/fiber/lightweight_thread/future/whatever_you_want_to_call_it scheduler. Anyway, monads are hard to compose, so the shiny new thing here is called "algebraic effects". http://www.eff-lang.org/ http://www.eff-lang.org/

tathougies 8y ago
> Anyway, monads are hard to compose, Monads don't compose because monads shouldn't compose. Many things form monads that do not form proper effects. Perhaps the most obvious is the typical continuation monad. It is a good thing that this particular monad does not compose because if it did, you'd be in for a ton of hurt in understanding what happened when. Effect systems are good when all you want to do is write code that has effects. Monads are not really about effects, although they can be used to describe certain classes of them. Monads are nevertheless, strictly more powerful.
- catern 8y ago
  >Effect systems are good when all you want to do is write code that has effects. Monads are not really about effects, although they can be used to describe certain classes of them. Monads are nevertheless, strictly more powerful. This is not true. Monads and effect systems are equally powerful. More concretely: Effect systems are essentially delimited continuations. Monads and multi-shot delimited continuations are equally powerful, though some effect systems don't support invoking the continuation multiple times and so aren't multi-shot and therefore are less powerful than monads. You can express any monad with delimited continuations, and vice versa. And using some monad in do-notation, and using the corresponding delimited continuation implementation in normal (non-Haskell) sequential code, will look identical.
  - tathougies 8y ago
    > You can express any monad with delimited continuations, and vice versa source please.

tathougies 8y ago

> Anyway, monads are hard to compose, Monads don't compose because monads shouldn't compose. Many things form monads that do not form proper effects. Perhaps the most obvious is the typical continuation monad. It is a good thing that this particular monad does not compose because if it did, you'd be in for a ton of hurt in understanding what happened when. Effect systems are good when all you want to do is write code that has effects. Monads are not really about effects, although they can be used to describe certain classes of them. Monads are nevertheless, strictly more powerful.

catern 8y ago
>Effect systems are good when all you want to do is write code that has effects. Monads are not really about effects, although they can be used to describe certain classes of them. Monads are nevertheless, strictly more powerful. This is not true. Monads and effect systems are equally powerful. More concretely: Effect systems are essentially delimited continuations. Monads and multi-shot delimited continuations are equally powerful, though some effect systems don't support invoking the continuation multiple times and so aren't multi-shot and therefore are less powerful than monads. You can express any monad with delimited continuations, and vice versa. And using some monad in do-notation, and using the corresponding delimited continuation implementation in normal (non-Haskell) sequential code, will look identical.
- tathougies 8y ago
  > You can express any monad with delimited continuations, and vice versa source please.