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I was a college dropout and self taught bash and python programmer and quite some time ago, I read about Haskell, decided to teach myself to use it, and then re

I was a college dropout and self taught bash and python programmer and quite some time ago, I read about Haskell, decided to teach myself to use it, and then realized I had absolutely no idea what programming actually was, and basically spent the next 15 years teaching myself computer science, category theory, abstract algebra and so on, so that I could finally understand Haskell code. I still don't understand Haskell, but it did help me learn Rust when I decided to learn that. And I think I could explain what a monad is. edit: It's a data structure that implements flat map. Hope this saves someone else a few years of their life.

bspammer 2y ago
I think that's a good starting definition for programmers, but still could cause confusion when you run into something like IO in Haskell. IO isn't really a data structure, and it's hard to fit the "flat map" concept to it.
- nextaccountic 2y ago
  If you want you can still keep this point of view, by saying that IO is conceptually a data structure that builds a description of what the program does. In this point of view it follows that there is another, impure program that interprets the IO data structure and actually performs the computations (Of course in practice IO isn't implemented like this, because it would be too slow) (But in every other language, like Javascript or Python, you can define IO as a data structure. Or even in Haskell itself, you can define for eg. a free monad that gets interpreted later, and it can be made to be just as good as IO itself, though typically people make it less powerful than IO) However note that every other "computational" monad (like the list monad or the Cont monad) actually is a data structure, even though they describe effects just like IO does. This is because IO is the only possible exception to the "monads are data structures" thing in Haskell (if you don't subscribe to the above view), because Haskell doesn't let you define types that aren't data structures The only issue with this point of view is that you now need to say what flatMap means for things that are not shaped like arrays. Eg. does it make intuitive sense to flatMap a tree? (A retort is that it must make sense, whatever you call this operation; and flattening a tree means to turn a tree of trees into an one-level tree)
crabbone 2y ago
> I still don't understand Haskell It's not you. Haskell has very bad syntax. It's not hard to understand it, it you rewrite the same things in something saner. Haskell was developed by people who enjoy one-liners and don't really need to write practical programs. Another aspect of Haskell is that it was written by people who were so misguided as to think that mathematical formulas are somehow superior to typical imperative languages, with meaningful variable names, predictable interpretations of sequences of instructions etc. They, instead, made it all bespoke. Every operation has its own syntax, variables are typically named as they would in math formulas (eg. X and X'). This makes no sense, and is, in fact, very harmful when writing real-world programs, but because, by and large, Haskell never raises to the task of writing real-world programs, it doesn't deter the adepts from using it.
- tome 2y ago
  That's what (some) other people do. None of that stops you writing Haskell in whatever style you want, with meaningful variable names, curly braces and semicolons!
  - crabbone 2y ago
    Unfortunately, writing isn't even half the battle. Before you start writing, you need to read a lot. And Haskell code is, in general, atrocious. It always feels like there was a normal way to do something, but the author decided to chose the most convoluted way they can imagine to accomplish the same thing for the sake of a bizarre fashion sense.
- agentultra 2y ago
  You knew Paul Hudak, Simon Peyton Jones, Phil Wadler, etc? Were they thinking about the benefits of mathematical formulas over program counters and procedural keywords when designing Haskell? I was under the impression from the History of Haskell [0] that they were interested in unifying research into lazy evaluation of functional programming languages. > This makes no sense, and is, in fact, very harmful when writing real-world programs, Gosh, what am I doing with my life? I must have made up all those programs I wrote on my stream, the ones I use to maintain my website, and all the boring line-of-business code I write at work. /s In all seriousness, Haskell has its warts, but being impractical isn't one of them. To some purists the committee has been overly pragmatic with the design of the language. As far as functional programming languages go it's pretty hairy. You have "pure" functions in the base libraries that can throw runtime exceptions when given the wrong values for their arguments (ie: the infamous head function). Bottom, a special kind of null value, is a member of every type. There exist functions to escape the type system entirely that are used with some frequency to make things work. The committee has gone back more than once to reshape the type-class hierarchy much to the chagrin of the community of maintainers who had to manually patch old code or risk having it not longer compile on new versions of the base libraries. These are all hairy, pragmatic trade-offs the language and ecosystem designers and maintainers have had to make... because people write software using this language to solve problems they have and they have to maintain these systems. [0] https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/history.pdf?from=https://research.microsoft.com/~simonpj/papers/history-of-haskell/history.pdf&type=exact https://www.microsoft.com/en-us/research/wp-content/uploads/...

bspammer 2y ago

I think that's a good starting definition for programmers, but still could cause confusion when you run into something like IO in Haskell. IO isn't really a data structure, and it's hard to fit the "flat map" concept to it.

nextaccountic 2y ago
If you want you can still keep this point of view, by saying that IO is conceptually a data structure that builds a description of what the program does. In this point of view it follows that there is another, impure program that interprets the IO data structure and actually performs the computations (Of course in practice IO isn't implemented like this, because it would be too slow) (But in every other language, like Javascript or Python, you can define IO as a data structure. Or even in Haskell itself, you can define for eg. a free monad that gets interpreted later, and it can be made to be just as good as IO itself, though typically people make it less powerful than IO) However note that every other "computational" monad (like the list monad or the Cont monad) actually is a data structure, even though they describe effects just like IO does. This is because IO is the only possible exception to the "monads are data structures" thing in Haskell (if you don't subscribe to the above view), because Haskell doesn't let you define types that aren't data structures The only issue with this point of view is that you now need to say what flatMap means for things that are not shaped like arrays. Eg. does it make intuitive sense to flatMap a tree? (A retort is that it must make sense, whatever you call this operation; and flattening a tree means to turn a tree of trees into an one-level tree)

crabbone 2y ago

> I still don't understand Haskell It's not you. Haskell has very bad syntax. It's not hard to understand it, it you rewrite the same things in something saner. Haskell was developed by people who enjoy one-liners and don't really need to write practical programs. Another aspect of Haskell is that it was written by people who were so misguided as to think that mathematical formulas are somehow superior to typical imperative languages, with meaningful variable names, predictable interpretations of sequences of instructions etc. They, instead, made it all bespoke. Every operation has its own syntax, variables are typically named as they would in math formulas (eg. X and X'). This makes no sense, and is, in fact, very harmful when writing real-world programs, but because, by and large, Haskell never raises to the task of writing real-world programs, it doesn't deter the adepts from using it.

tome 2y ago
That's what (some) other people do. None of that stops you writing Haskell in whatever style you want, with meaningful variable names, curly braces and semicolons!
- crabbone 2y ago
  Unfortunately, writing isn't even half the battle. Before you start writing, you need to read a lot. And Haskell code is, in general, atrocious. It always feels like there was a normal way to do something, but the author decided to chose the most convoluted way they can imagine to accomplish the same thing for the sake of a bizarre fashion sense.
agentultra 2y ago
You knew Paul Hudak, Simon Peyton Jones, Phil Wadler, etc? Were they thinking about the benefits of mathematical formulas over program counters and procedural keywords when designing Haskell? I was under the impression from the History of Haskell [0] that they were interested in unifying research into lazy evaluation of functional programming languages. > This makes no sense, and is, in fact, very harmful when writing real-world programs, Gosh, what am I doing with my life? I must have made up all those programs I wrote on my stream, the ones I use to maintain my website, and all the boring line-of-business code I write at work. /s In all seriousness, Haskell has its warts, but being impractical isn't one of them. To some purists the committee has been overly pragmatic with the design of the language. As far as functional programming languages go it's pretty hairy. You have "pure" functions in the base libraries that can throw runtime exceptions when given the wrong values for their arguments (ie: the infamous head function). Bottom, a special kind of null value, is a member of every type. There exist functions to escape the type system entirely that are used with some frequency to make things work. The committee has gone back more than once to reshape the type-class hierarchy much to the chagrin of the community of maintainers who had to manually patch old code or risk having it not longer compile on new versions of the base libraries. These are all hairy, pragmatic trade-offs the language and ecosystem designers and maintainers have had to make... because people write software using this language to solve problems they have and they have to maintain these systems. [0] https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/history.pdf?from=https://research.microsoft.com/~simonpj/papers/history-of-haskell/history.pdf&type=exact https://www.microsoft.com/en-us/research/wp-content/uploads/...