[grogenaut]

Many people who like scheme and functional languages have an averse reaction to more procedural or OOP languages. It's interesting that people don't grok it can go the other way. But this is HN so I guess I'll explain.

A few things (and for context this was 1996).

With the class I disliked they were trying to teach me a language and a complex concept at the same time. In a 4 month semester, half of it was spent just getting basically proficient in the language. So instead of learning one concept I'm learning 2. We were essentially using scheme to build a interpreter for a simplified scheme. I understand why we were implementing scheme, it's one of the simplest languages to implement and maps well to many concepts in CS. this is actually why the game studio I worked at used it, not that it was the right language, in fact it's caused a lot of trouble and they have a lot of c/python like in the language now

Scheme seemed like a pretty useless language as well. The book for it listed (in the forward) out how amazing it was and showed all the amazing projects done with lisp-like languages. That list started with emacs and then the rest was academic things I'd never heard of, which seemed like a joke. If I recall scheme had some pretty weak language library functions at the time as well. Also at the time I cared about drawing triangles on the screen.

[I will lose points for this but it's my POV] I tend to find people who strongly like functional languages a bit insufferable, especially academics. I tend to learn by getting a real world project done, and I like tools that let you build real world things. I don't care anywhere near as much about form of the solution. . Functional languages seem to gel better with people who care about the beauty of a simple proof. I hate proofs. Also in much of the work I've done, the folks who really pushed for functional languages didn't really understand that most of their coworkers were juts not capable of understanding those languages or thinking that logically. There's a reason (imho) that they're not as popular of languages.

I have written stuff in these languages since then. I did work in the (gp reference) scripting language and on its implementation in the engine. This got me real features (like a mission in an AAA game, and features for my mission designers in the engine). This seemed useful to me.

I spent about 3 months trying to use Clojure to do a highly parallel data processing work. It seemed to map well to the problem. However it was insufferably slow, and with required type hinting was essentially complicated java (lost the benefit). I re-wrote it in C++ in about a week and brought the processing time from 15 minutes to 32 seconds by leveraging the deeper parts of the machine (buffers, disk cache, physical cores) which were not as available inside the abstraction.

So it also comes down to I haven't found a problem that maps well to something like scheme that I need to solve. When I do stuff with interpreters I just grab ANTLR and java/go/c++. This is more maintainable for everyone I work with.

[agumonkey]

I think some points are unfair. I have physical anger when I use java prior 8, but I do appreciate smalltalk a lot more, it tickles my sense of curiosity, joy.

While I do admit that lisp/scheme/fp seek beauty.. it's also one thing I want in coding. Beautiful code. Not at the expense of practicality.. but still, look at how easy it is to be confused and make a mess trying to write a flatmap like procedure, while in lisp it's so trivial you never even think about it.

Thanks for the honesty and good job on making things fast.

[grogenaut]

Oh I never said it's fair, just laying it out there for you to take however you wish. It's pretty obvious to me I've got an inherent bias towards functional programming. I see people who love it and are successful with it so it obviously works. I've never had cause to work it out though. Just like I never owned a Sega Saturn nor a X-Box One. It's my personal opinion and thoughts on a language. You don't have to agree with it! In fact I'm very sure you don't. But for every preferential opinion you have, someone else will have a different one.

For flatmap, looked up https://rosettacode.org/wiki/Flatten_a_list#Common_Lisp, this is just gibberish to me currently. Is this simple, or am I missing something?

I once had an discussion with someone who was a huge relational guy who could not understand dynamo (many have this issue). I asked him how to do a global postal address in a relational db. He proceeded to put out a ~5 table layout on the whiteboard from memory. Finished by saying of course there are other situations and you can handle them with X or Y. We went and grabbed a drink and I had him grab get a sde1 and explain that layout to the SDE1. I cut it off after 15 minutes. While it was OBVIOUS to him in his experience, it was in no way simple and the SDE1 (who was just starting multi-table joins) was taking a while to catch up. The sr eng was just used to relational. The model he had on the board was at least 30 years of iteration and best practices, practically it's own microservice. I drew it in dynamo where it's just PK:UserId, and then a bunch of optional columns. SDE1 grokked this right away.

I would love to know what types of apps / code / work you do that you really appreciate in lisp. As I said I'm always looking for a language to solve a problem. What class of applications do you use it for?

For instance I use C++ when I need to be near the metal (game engines, shaders, arduino). We use go at work but Scheme or Clojure might be better for the business logic we do (tho it'd be slower). Always wanted to use Erlang but I never got on the distributed chat program projects (I killed 2 acutally).

[agumonkey]

Wow if you consider flatten gibberish I have nothing to say to you that can convince you..

Talking about bare metal and video games, take a peek at https://en.wikipedia.org/wiki/Game_Oriented_Assembly_Lisp

Mind you this guys are far above average, but you can't get more perf + low level than this.

I think in time you'll realize how nice other paradigms can be, even if they look alien for quite some time.

[kazinator]

The flatten code is very simple. You can probably guess what defun is, but you have to know what is cond, atom, and the symbol nil (and its relation to lists), as well as the mapcan function, not to mention the #' notation that appears on the self-reference to flatten.

cond is a multi-branch conditional test: it has the syntax

   (cond (test0 code ...)
         (test1 code ...)
         (test2 code ...)
         ...)

The tests are evaluated in sequence. When the first one is encountered that yields true, then the associated code is evaluated. cond then terminates, and yields the value of the last expression that was evaluated.

A catch-all clause, if necessary, is put at the end, where the test expression is just the symbol t. This symbol is Lisp's canonical representation of Boolean true. Though, any object other than nil is true, it is good form to use the t symbol as a Boolean true constant. Such a catch-all clause appears in the flatten implementation's cond.

atom tests whether a value is an atom, which means "not a cons cell". All objects that are not conses are atoms. Non-empty lists are made of conses: a three element list has three conses. The empty list is made of no conses; it is represented by the symbol nil, which is an atom.

null tests whether a value is the nil object: (null X) is the same thing as (eq nil X).

list is a constructor that makes a list of its argument values.

mapcan projects a each element of a list through a function. The values returned by the function must be lists, and those lists are catenated together. The catenated list is returned by mapcan (destructively, not functionally!) Obviously, mapcan is relevant to implementing flatten.

The #'X notation is a shorhand for (function X). It's a special operator which obtains a function as a value, given its name. It is necessary due to the two-namespace nature of Common Lisp: function bindings are in a separate namespace from variable bindings. If there is a function called X, the (X ...) expression calls the function well enough, but the expression X doesn't retrieve the X function; it refers to an X variable. (function X) refers to the function as a value, and because that is verbose, it has a #'X shorthand.

Note that the flatcan expression recurses on the list elements without regard for whether they are lists or not. For instance, if we flatten (1 2 3), then flatten will get recursively called for 1, 2, and 3. These 1, 2, 3 cases will be detected by the (atom structure) branch of the cond. (1), (2) and (3) will be returned, which get catenated by mapcan to (1 2 3) again.

[gen220]

I think your view’s totally reasonable. In my experience, the benefit of FP is To teach good program design: I’ve observed that functional programming languages encourage good practices that can be practiced in any language. For example: pushing I/O to the leaves of your program, dependency injection, eradicating global state, focus on functional interfaces.

These are patterns that you can do in any language, but functional languages kind of compel you to follow them. Many people first learned these patterns from FP, and carry them over to OOP, which they have to write at work.

I don’t know if there are many problems that are elegantly defined for FP, as you suggest. I think people just get comfortable in their cages. :)

[pantaloony]

You’re not alone. My brain works in steps, not proofs. If all code looked like Haskell and friends I doubt I’d ever have gotten into it in the first place.

[edit] algos, over proofs, would probably be a better way to put it.

[vvv312]

Proofs work in steps too.

I can never tell what an index-juggling loop is doing, in whatever language (including Scheme).

But when you follow the data type case by case, each step is simple and logical, easy to comprehend so the whole solution is easy too.

[pantaloony]

Sure, which is why I edited that “algorithms” is more accurate. When I read proofs I have to go through each step and figure out what every term on either side “does” to something “going through” it to make sense of it. I’d rather have my sandwich-making instructions as instructions than a series of statements about how the sandwich looks at each stage that I have to go back and turn into instructions to actually do anything with it, if that makes sense.

I get that other people don’t have this preference, but I strongly do. Test results indicate I should be incredibly well suited to mathematical work but I feel the way I imagine a dyslexic must when I try to read math or “mathy” programming languages. Give me something more-or-less procedural and I’m totally happy (though I gather I had a much easier time understanding and getting comfortable with recursion than many people do, which seems weird given I find the languages most heavily associated with it almost unreadable).

[agumonkey]

proofs to me, are 'typed' steps. you explicitely state the domains