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Everything old is new again. This challenge is basically why monads exist, because the monad allows you to cleanly separate between the state in which the algor

Everything old is new again. This challenge is basically why monads exist, because the monad allows you to cleanly separate between the state in which the algorithm is running and the algorithm itself. Reminds me of: https://philipnilsson.github.io/Badness10k/posts/2017-05-07-escaping-hell-with-monads.html https://philipnilsson.github.io/Badness10k/posts/2017-05-07-... I wonder what poor abstraction the Go authors will come up with instead?

philosopher1234 6y ago
How would you apply monads to solve the context problem? Hard for me to imagine what that would look like
- dllthomas 6y ago
  I think what they have in mind is a Reader monad. newtype Reader r a = Reader { runReader :: r -> a } instance Monad (Reader r) where pure x = Reader (\ _ -> x) m >>= f = Reader (\ r -> runReader (f (runReader m r)) r) which allows us to define: getContext :: Reader r r getContext = Reader (\ r -> r) and which spares us threading the context manually. I don't think that's such a big deal, so long as there's only one thing we're threading. In some languages, we can be generic over "contexts which provide the thing I want, whether they do other things or not", which is sometimes a much bigger win.
- solatic 6y ago
  Context is like Schrödinger's Cat, you don't know if the Context you're working in is alive or dead (i.e. cancelled, timed out, etc.), but you have to keep passing it forward, one intermediate network call after the next, as long as its status is uncertain. Only when the request fully returns, or is actively cancelled, do you know whether the request is alive or dead. The Maybe monad deals with the same issue. You have a series of function calls, each of which might or might not be legal, because you never know if you actually have the parameter for the next function call. Maybe you do, maybe you don't. If you take the naive approach to solving the issue, you pass along Schrödinger's Cat each step along the way. You intertwine the concern of the algorithm you're trying to write with the uncertainty of whether you're carrying a live cat or a dead one. It can work, but it's ugly. The monadic approach allows you to separate these concerns. You write your algorithm as if you know for a fact that the cat is alive. If the cat were ever to be revealed to be dead along the path, it doesn't matter, the monad separated the consequences of dealing with the live or dead cat from the rest of your algorithm. The rest of your algorithm simply doesn't get run. Context is the same. You get to write code as if the context is always valid. You don't have to worry about context being cancelled, or timed out, or anything else. You take all those concerns and relate to them separately, in one place, where they can be neatly dealt with. The whole point of the monadic pattern is to propagate state in such a way that it doesn't interfere with the pure algorithm which you're trying to write. You write the pure algorithm separately, and then use it within the monadic context of Context, so to speak.
voldacar 6y ago
the gophers hated him because he told them the truth
nyanpasu64 6y ago
> https://philipnilsson.github.io/Badness10k/posts/2017-05-07-escaping-hell-with-monads.html https://philipnilsson.github.io/Badness10k/posts/2017-05-07-... Every "monadic solution" prints the same code block without explaining how it would work, the types of the various variables, the semantics of the <- operator. I didn't leave the page with an understanding of how monads achieve these tasks.
- virtue3 6y ago
  The article is literally: "Hell thing" Step 1 -> monads step 2 -> ???? step 3 -> profit? This is apparently the monads curse where people that get them can't effing explain them to save their life.
  - strbean 6y ago
    Monads are just monoids in the category of endofunctors! /s The issue is pretty much a language barrier. All these articles talking about benefits of / interesting ways to use monads are written by people who speak the language, assuming the reader speaks the language as well. As with many functional programming topics, the fundamentals aren't incredibly easy to wrap your head around. But if you already understood monads, can you imagine how annoying it would be if every resource, discussion, article, etc. relating to them started with a pages-long introduction on What is a Monad? In Haskell, this is a fundamental topic. Monads are used everywhere. If people always explained how they worked when discussing them, it would be like looking up sorting algorithms and having every algorithm description start with a long-winded explanation of how for loops work.
    - infogulch 6y ago
      > But if you already understood monads, can you imagine how annoying it would be if every resource, discussion, article, etc. relating to them started with a pages-long introduction on What is a Monad? I agree that it would be unreasonable for every article that uses monads to describe what they are. But I don't think it would be unreasonable for every one of them to link to another article that does explain them.

philosopher1234 6y ago

How would you apply monads to solve the context problem? Hard for me to imagine what that would look like

dllthomas 6y ago
I think what they have in mind is a Reader monad. newtype Reader r a = Reader { runReader :: r -> a } instance Monad (Reader r) where pure x = Reader (\ _ -> x) m >>= f = Reader (\ r -> runReader (f (runReader m r)) r) which allows us to define: getContext :: Reader r r getContext = Reader (\ r -> r) and which spares us threading the context manually. I don't think that's such a big deal, so long as there's only one thing we're threading. In some languages, we can be generic over "contexts which provide the thing I want, whether they do other things or not", which is sometimes a much bigger win.
solatic 6y ago
Context is like Schrödinger's Cat, you don't know if the Context you're working in is alive or dead (i.e. cancelled, timed out, etc.), but you have to keep passing it forward, one intermediate network call after the next, as long as its status is uncertain. Only when the request fully returns, or is actively cancelled, do you know whether the request is alive or dead. The Maybe monad deals with the same issue. You have a series of function calls, each of which might or might not be legal, because you never know if you actually have the parameter for the next function call. Maybe you do, maybe you don't. If you take the naive approach to solving the issue, you pass along Schrödinger's Cat each step along the way. You intertwine the concern of the algorithm you're trying to write with the uncertainty of whether you're carrying a live cat or a dead one. It can work, but it's ugly. The monadic approach allows you to separate these concerns. You write your algorithm as if you know for a fact that the cat is alive. If the cat were ever to be revealed to be dead along the path, it doesn't matter, the monad separated the consequences of dealing with the live or dead cat from the rest of your algorithm. The rest of your algorithm simply doesn't get run. Context is the same. You get to write code as if the context is always valid. You don't have to worry about context being cancelled, or timed out, or anything else. You take all those concerns and relate to them separately, in one place, where they can be neatly dealt with. The whole point of the monadic pattern is to propagate state in such a way that it doesn't interfere with the pure algorithm which you're trying to write. You write the pure algorithm separately, and then use it within the monadic context of Context, so to speak.

voldacar 6y ago

the gophers hated him because he told them the truth

nyanpasu64 6y ago

> https://philipnilsson.github.io/Badness10k/posts/2017-05-07-escaping-hell-with-monads.html https://philipnilsson.github.io/Badness10k/posts/2017-05-07-... Every "monadic solution" prints the same code block without explaining how it would work, the types of the various variables, the semantics of the <- operator. I didn't leave the page with an understanding of how monads achieve these tasks.

virtue3 6y ago
The article is literally: "Hell thing" Step 1 -> monads step 2 -> ???? step 3 -> profit? This is apparently the monads curse where people that get them can't effing explain them to save their life.
- strbean 6y ago
  Monads are just monoids in the category of endofunctors! /s The issue is pretty much a language barrier. All these articles talking about benefits of / interesting ways to use monads are written by people who speak the language, assuming the reader speaks the language as well. As with many functional programming topics, the fundamentals aren't incredibly easy to wrap your head around. But if you already understood monads, can you imagine how annoying it would be if every resource, discussion, article, etc. relating to them started with a pages-long introduction on What is a Monad? In Haskell, this is a fundamental topic. Monads are used everywhere. If people always explained how they worked when discussing them, it would be like looking up sorting algorithms and having every algorithm description start with a long-winded explanation of how for loops work.
  - infogulch 6y ago
    > But if you already understood monads, can you imagine how annoying it would be if every resource, discussion, article, etc. relating to them started with a pages-long introduction on What is a Monad? I agree that it would be unreasonable for every article that uses monads to describe what they are. But I don't think it would be unreasonable for every one of them to link to another article that does explain them.