Why I still reach for Lisp and Scheme instead of Haskell

> Lisp hackers have been effortlessly reshaping the language for decades using the powerful macro system and extending and bending the language to their will.

I've written a bit of Racket code (https://github.com/evdubs?tab=repositories&q=&type=&language...) and I still haven't written a macro. In only one case did I even think a macro would be useful: merging class member definitions to include both the type and the default value on the same line. It's sort of a shame that Racket, a Scheme with a much larger standard library and many great user-contributed libraries, has to deal with the Scheme/Lisp marketing of "you can build low level tools with macros" when it's more likely that Racket developers won't need to write macros since they're already written and part of the standard library.

> But the success of Parsec has filled Hackage with hundreds of bespoke DSLs for everything. One for parsing, one for XML, one for generating PDFs. Each is completely different, and each demands its own learning curve. Consider parsing XML, mutating it based on some JSON from a web API, and writing it to a PDF.

What a missed opportunity to preach another gospel of Lisp: s-expressions. XML and JSON are forms of data that are likely not native to the programming language you're using (the exception being JSON in JavaScript). What is better than XML or JSON? s-expressions. How do Lisp developers deal with XML and JSON? Convert it to s-expressions. What about defining data? Since you have s-expressions, you aren't limited to XML and JSON and you can instead use sorted maps for your data or use proper dates for your data; you don't need to fit everything into the array, hash, string, and float buckets as you would with JSON.

If you've been hearing about Lisp and you get turned off by all of this "you can build a DSL and use better macros" marketing, Racket has been a much more comfortable environment for a developer used to languages with large standard libraries like Java and C#.

  true:  t
  false: nil
  null:  :null
  []     #()
  {}     (make-hash-table :test #'equal)

> Of course, to be completely fair about my toolkit, standard Scheme can sometimes lack the heavyweight, “batteries-included” ecosystem required for massive enterprise production compared to the JVM.

I was thinking the whole time, "this person would _love_ Clojure".

> You can pause, inspect objects, change values, and even redefine a broken function on the fly to test a fix in any environment (yes even in production, while running).

I see this mentioned often, and it sounds amazingly useful (especially the part about fixing in production!). But how truly widespread is it among the Lisp dialects to be able to connect to a running program, debug, and hotfix it? I understand Common Lisp has it, but I struggled to figure out how to do it in, say, Racket. Admittedly I'm am relatively inexperienced Lisp programmer, so maybe I wasn't looking in the right place or for the right words. Which Lisp dialects do indeed support the extreme version of this capability to inspect and edit running programs?

> Actually, in my opinion, Scheme (and Lisp) allows you to express complex systems and problem domains in more simple terms than any other language can.

Short article. Worth reading. But all I swallowed was this one sentence.

Its the sytax. If you like semicolons, thats why you like Pascal-like languages.

I think I much prefer Haskell DSLs over Lisp macros as the basis for APIs in foreign code. That might be due to my relative inexperience with Lisps, but macros just seem to make all the bad aspects of dynamically typed langues much worse. Looking at some piece of code in isolation, not only is it often impossible to tell what is the type/shape of data that are coming in (as is common with dynamic type systems) but with macros added to the mix I also can't tell what the control flow is. So to understand what a single piece of code is doing, I find myself chasing for hints that are scattered throughout the entire codebase.

Contrast this to Haskell's use of DSLs – although they really can be quite dense sometimes, I feel like, when I get stuck, I can always just dig into the documentation on Hackage, and figure out things from the type definitions (even when explanations in docs are lacking). Though it does require being comfortable with the abstractions being used (monads and such). Rust is similar in this manner but to a lesser extent.

But again, maybe the macro critique stems from my inexperience with them.

(In Haskell) > just adding a simple print somewhere is not going to work without refactor

Interesting. How do people cope with this in practice? Does it mean you can't really use log() -statements for debugging?

I learned Scheme before Haskell and as much as I enjoyed the experience, I still wouldn't reach for Haskell first. It's pretty much limited to my xmonad configuration.

> Actually, in my opinion, Scheme (and Lisp) allows you to express complex systems and problem domains in more simple terms than any other language can.

I disagree with this. Lisps are procedural languages like most other programming languages. They can describe procedures in a relatively simple manner (big asterisk on that one, the simplicity of Lisp as a language is greatly overstated and conflated with the simplicity of s-expressions), but procedures aren't really good at expressing complex systems or problem domains. In my experience, relational languages like Prolog are vastly better at this. Lisps are much easier for the average programmer to pick up and write reasonably performant code with, though.

   (progn a b c)      ;; CommonLisp
   (begin a b c)      ;; Scheme
   ($sequence a b c)  ;; Kernel

   ;; evaluate a, then b, then c, 
   ;; ignore the results of evaluating a and b 
   ;; return the result of evaluating c.

   (define (foo)
       (expr1)
       (expr2)
       (expr3))

    (define foo (lambda () (begin (expr1) (expr3) (expr3))))

    (define (foo) (prog1 (expr1) (expr2) (expr3))
    (foo)
 
    ;; evaluates expr1, then expr2, then expr3
    ;; returns the result of evaluating expr1
    ;; ignores the results of evaluating expr2 and expr3

Seems a bit similar to 'Why I prefer Scheme to Haskell' (<https://news.ycombinator.com/item?id=3816385>, 2012). Seems a bit plagiarized, but that may just be a coincidence.

If you know lisp, just reach for Coalton instead of Haskell

Picking a language is a matter of selecting the best fit given the constraints of the project.

For stuff I like to work on on my own time, "how I like to work" is a major forcing constraint. So it's no surprise that I have a large number of Lisp projects sitting around. Maybe it's because I'm auDHD, but the ability to evolve a program through active dialogue with the machine (and not of the sloppotron variety) just fits better with how I think through a problem and its solution.

Because they're elegant. Haskell is a conceptual and syntax mess.

Irrespective of the language, I love the REPL. For this reason, among others, I just cannot get into Agentic Coding. It seems like a step back to batch processing.

I don't believe monads are a "heavy handed abstraction" and that's what prevents people from prototyping in Haskell.

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.

> Remember that later, just adding a simple print somewhere is not going to work without refactor (welcome to the IO monad).

This hits home for me. Print statements are essential to the way I code. I use them to debug, to examine variables and parameters, to trace execution flow. I rarely use debuggers.

Haskell is godsend when using LLMs though.

I tried some ML language once, it's difficult even to write a basic factorial example, which in Scheme I could do it iteratively and recursively with ease.

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.