Posted by jjba23 20 hours ago
What really prevents people from writing in Haskell at a reasonable speed is the poor language design. Programming languages are supposed to aid in reading by emphasizing structure. It's important to emphasize that a particular group of "words" constitutes a function call, or a variable definition, or a type definition -- whatever the language has to offer.
Haskell is a word salad. Every line you read, you have to read multiple times, every time trying to guess the structure from the disconnected acronyms. It belongs to the "buffalo buffalo buffalo buffalo" gimmick family. This is a huge roadblock on the way to prototyping as well as any other activity that implies the ability to read code quickly. And then it's also spiced by the most bizarre indentation rules invented by men.
This is not at all a problem with eg. SML or Erlang, even though they are roughly in the same category of languages.
Haskell would've been a much better language if it made its syntax more systematic and disallowed syntactical extensions s.a. introduction of user-invented infix operators, overloading of literals (heaven, why???) and requiring parenthesis around function arguments both for definition and for application. The execution model is great, the typesystem is great... but the surface, the front door to all these nice things the language has is just some amateur level nonsense.
* * *
As for the upsides of using languages from the Lisp family for practical problems... I don't find (syntax-rules ...) all that exciting. I understand this was an attempt to constrain the freedom given by Common Lisp macros, and I don't think it worked. I think it's clumsy and annoying to deal with. The very first time I tried to use it, I ran into its limitations, and that felt completely unjustified. To prototype, you want freedom of movement, not some pedantry that will stand in your way and demand you work around it somehow.
The absolute selling point, however, is SWANK. Instead of editing the source code, you are editing the program itself, that can be interacted with in points of your choosing. I don't know of any modern language that offers this kind of experience. I think, even still in the 80s, this approach to programmers interacting with computers was common. At school, we had terminals with some variety of Basic, and it worked just like that: you type the program and it instantly shows the effect of your changes. Then, there was also Forth, which also worked in a similar way: it felt like you are "talking" to the computer in a very organized and structured way, but real-time.
Most mainstream languages today sprouted from the idea of batch jobs, where the programmer isn't at the keyboard when the program runs. They came with the need to anticipate and protect the programmer from every minor mistake they might've easily detected and fixed during an interactive session far, far in advance.
Whenever I think about writing in C, or Rust, or Haskell, I imagine being tasked with going to the grocery blindfolded: I'd need to memorize the number of steps, the turns, predict the traffic, have canned strategies for what to do when potatoes go on sale... I deeply regret that programming evolved using this evolution path, and our idea of what it means to program is, mostly, the skill of guessing the impossible to predict future, instead of learning to react to the events as they unfold.
Syntax highlighting? Please take a look at https://play.haskell.org/
I am completely baffled by this comment. Are you missing the parenthesized function calls by any chance? If so then I can relate a bit.
syntax-case is the general purpose construct to use. syntax-rules is a restricted, easy-things-should-be-easy construct.
I couldn't disagree more. Yes, there is more upfront work understanding Haskell code. But it's very dense. Once you understand the patterns, you can read it much quicker. Just like map/filter/fold are harder to understand then a for-loop, but once you do, you can immediately see what kind of iteration is applied. The for-loop can do all kinds of crazy index manipulation that you always have to digest from scratch.
> And then it's also spiced by the most bizarre indentation rules invented by men.
Again, quite surprised by this criticism. The rule is extremely simple: inner expressions must be indented more. You're free to decide by how much. That's why there are many "styles" out there. Maybe that's what you mean with bizarre. But it's not like the language is forcing weird constraints on you. If anything the constraints are too lax. Any other language with non-mandatory indentation allows that as well. In general, I really don't understand why not more languages do mandatory indentation. You only need curly braces and semicolons if you want the option to write a whole if/else/while/... statement in one line. But nobody does that.
Not to support the parent comment, which I disagree with, but If you use multi-line let-bindings, those require that you indent not just more than the previous line, but as much as the first token after the let keyword on the previous line. It’s a very strange rule, all the more surprising because it’s inconsistent even with the rest of the language. It is totally avoidable if you, like I think most experienced haskellers do, just prefer ‘where’, but people more familiar with procedural code usually lean into using ‘let’ everywhere because it feels more familiar.
I think the strange indentation used to be required in more places - I vaguely remember running into it a lot more when I started with Haskell 20 years ago, but that was also just when I was new to the language. These days I just keep ‘let’ to a bare minimum, so it doesn’t bother me. One thing that made Elm frustrating was that it disallowed ‘where’ clauses, forcing you to deal with this weird edge case all the time.
let
f = 9
fo = 10
foo = 123
in f+fo+foo
let
f = 9
fo = 10
foo = 123
in f+fo+foo someValue = let f = 9
fo = 10
foo = 123
in f+fo+foo
someValue = let f = 9
fo = 10
foo = 123
in f+fo+foo
This is fine:
someValue = let
f = 9
fo = 10
foo = 123
in f+fo+foo
I honestly think it would be less surprising if the parser just disallowed writing the first binding on the same line as the `let` entirely, treating it only as a block, but some people (bewilderingly) do seem to prefer to write their code with the excessive indentation (I'd imagine with editor support, rather than manually maintaining the spacing).
Are you mixing tabs and spaces? Maybe an example here would help.
>overloading of literals (heaven, why???)
No, this is important, so that default strings don't to have to be something crummy. Even C++ got on this bandwagon.
>and requiring parenthesis around function arguments both for definition and for application.
??? Again, an example would be helpful. Usually the complaint with Haskell is that people don't use enough parenthesis.
>The execution model is great
...I thought lazy execution was widely agreed to be the worst part of Haskell.
Either with S9 Scheme for quick fun (it has Unix sockets and ncurses :D ) or Chicken Scheme for completeneless (R5RS/R7RS-small + modules), I always have fun with both.
Oh, and well, Forth, too, but more like a puzzle (altough it shines to teach you that you can do a lot with a fixed point). Hint: write helpers for rationals -a/b where a is an integer and b a non-zero integer- and complex numbers by placing two items in the stack for each case (for rat helpers you need four (a/b [+-*/] c/d) .
You can have a look at qcomplex.tcl (either online or installed) as an example on how can it work even under JimTCL itself by just sourcing that file. Magic, complex numbers under jimsh thanks to the algebraic properties. So, you can implement the same for yourself in some Forths, even under EForth for Muxleq. Useless? It depends, under an ESP32 it can be damn fast, faster than Micropython.
Racket:
> (define (fact n)
(if (= n 1)
1
(* n (fact (- n 1)))))
> (fact 6)
720
# let rec fact = function
| 1 -> 1
| n when n > 1 -> n * (fact (n - 1))
in fact 6;;
- : int = 720 fac n = product [1 .. n]https://people.willamette.edu/~fruehr/haskell/evolution.html
fac 1 = 1
fac n = n * (fac (n - 1))
I mean, in Scheme it is longer to write. I enjoy Lisps and use Emacs for everything, but Haskell can be as terse, or even more terse. (Which is not always a good thing.)
What do you mean? It's one of the first things taught in any tutorial for the ML family or Haskell.