Hacker News

by Ryan Harman

A Friendly Introduction to Racket (geometridae.bearblog.dev)

107 points by signa11 7 hours ago

0x3444ac53 2 minutes ago

Mild nitpick, but on Janet https://news.ycombinator.com/item?id=26496339

GregBuchholz 2 hours ago

> no special syntax for anything.

    (list '(1. . #\#)
          -5/6+7.s-8i
          `(1 ,@2)
          1@1           ;hmmm, no unquote splicing comma ;-)
          10#           ;surprised?
          (list #i+1 +1i 1+i) ;complicated or complex?
          #e-1e10i     ;Old MacDonald?
          "(* 9 10)" #())

soegaard 13 minutes ago

Yeah - the number syntax is pretty cool.

    #i is the prefix for inexact
    #e is the prefix for exact
So `#e0.1` is exact 0.1 which means it will be read as an exact fraction 1/10 and `#i0.1` will be read as a floating point number.

The `i` in `8i` is the imaginary unit. The `1@1` is the polar notation for complex numbers.

The `10#` is a compatibility remain (the Scheme authors wanted a way to see how many signifant digits were known. In `10#` there 2. So `#` stands for "some digit". In most implementations this is read as 0. More details at [1]

An `#` followed by a list datum is read as a vector. Thus `#()` is an empty vector and `()` is an empty list.

[1] https://stackoverflow.com/a/10936403/23567

Complicated? Well, to support both inexact (floating point) and exact numbers (bignums and fractions) it makes sense to have `#i` and `#e` to explicitl choose. The default is (more or less): numbers with . are inexact the others are exact.

Syntonicles 10 minutes ago

At first I was frustrated by this comment, having a fair amount of Lisp experience failing to grok the examples. In less than one minute I was able to locate, download and install the latest Racket and was in a REPL. There really are no excuses.

This was a wild ride. I'm torn on whether this feels like the Reader is bloated/polluted or whether this is the coolest numerical parser I've ever used. You can really do a lot to coerce the these numbers just by inserting an {o,s,e,i,b,#} into the number, with different semantics depending on the position of the character.

Somewhat overwhelming, I can only hope there's some elegance underlying it all...

nilslindemann 18 minutes ago

Curious, how would look that in Python?

jqpabc123 an hour ago

It looks more like a "program" for an HP15c pocket scientific calculator.

Not necessarily a bad thing but also not exactly what I would call "expressive".

You may be able to build anything you want --- which may be efficient when communicating with the machine. But I wonder about now well this would communicate with other programmers.

jibal 27 minutes ago

It's not a program, it is (obviously) a totally unrealistic hodgepodge expression for a list of constant values that simply demonstrates the literal syntax for a variety of types of values (real numbers, dotted pairs, rational numbers, complex numbers, polar coordinates, etc. -- Racket is unusually expressive in the types of literals). Your comment demonstrates something typical of HN, and it's not a good thing. It's as if in a discussion about C someone posted, without explanation, an entry from the Obfuscated C contest and then someone else, making zero effort to understand what was posted, said that it looked like line noise and questioned whether C is conducive to communication between programmers.

perrygeo 5 hours ago

> In The Amazing Digital Circus (episode 8, "hjsakldfhl"), when Kinger opens the terminal to try to reset Caine, you can see that Caine (a creative AI built in 1996) is programmed in Lisp. The file is literally named Caine-core.lisp.

Nice touch. Explains how Caine returns in episode 9: Lisp continuations allow for graceful error recovery.

valorzard 4 hours ago

wasn't Caine written in common lisp? Pretty sure they show that the debugger they used in the command line was gdb (which ... is that even actually possible?)

perrygeo 3 hours ago

Yep, `/usr/bin/gdb /usr/local/bin/clisp 1337` ... also in TADC lore, windows has forward slashes.

GregBuchholz an hour ago

fn-mote 4 hours ago

Much as I am a fan of Racket, this is not a friendly intro. It is a speedrun.

When an introduction says “friendly”, I don’t expect it to assume that I know what lambda is.

When an introduction says “friendly”, I don’t expect syntax rules to appear in it. At all.

allthetime 2 hours ago

It is rich with information, to the point, and presented in a way that a motivated and competent reader can immediately know something about and be useful with racket. That’s how it was for me anyways; someone who didn’t know anything about racket before reading through this.

Wtf kind of intro to a programming language doesn’t include syntax rules? We are all informed, experienced, technologically inclined people here. Not dumb children.

I’m struggling to see your comment as anything more than contrarian babble.

sudahtigabulan 2 hours ago

> Wtf kind of intro to a programming language doesn’t include syntax rules?

PP could have been more clear and say syntax-rules (note the dash), which means macros. Macros are usually considered an advanced topic.

wormius an hour ago

dented42 2 hours ago

> Wtf kind of intro to a programming language doesn’t include syntax rules?

Given that most languages don’t have syntax rules or anything like it, I’m gonna go out on a limb and say that most language introductions/overviews/tutorials don’t mention it.

AnimalMuppet 40 minutes ago

phlakaton 2 hours ago

When I see "friendly introduction," I don't expect to see a deadhead sticker front and center. But I guess if you're an actual Deadhead it's not that startling. ;-)

wormius an hour ago

TBF, deadheads are pretty friendly (just stay away from the Nitrous Mafia) LOL.

y1n0 an hour ago

not to mention a skull? is it a racket thing (or lisp in general thing) to spoof the grateful dead logo?

ux266478 32 minutes ago

Nothing against Lisp, but to correct the record:

> For decades, Lisp was the language of artificial intelligence. [...] Then came the "AI winter," funding dried up, and Lisp went from star to cult language.

Lisp had fallen from relevance before then. Only the United States was still using it, and mostly out of technical debt and a stubborn refusal to move on. Prolog displaced it in the late 1970s, and even within the US, the Lisp part was an unfortunate implementation detail to get to a Prolog-shaped object. It's not surprising that the US fell way behind Japan in this area in the 1980s. Anybody who would imply they would take a Lisp machine over a PIM is either not interested in symbolic computation and just likes Lisp, or they're doing so out of total ignorance of how much more advanced the PIMs were for symbolic AI.

The cutting edge was with Prolog, and that's still the case today. Nobody's researching MIL in Lisp, even in America.

zerr 3 hours ago

While the language is interesting, sadly, nobody is using it in the wild. Maybe due to cumbersome deployment options? The ability to produce native standalone executables would boost its usage I believe.

throwaway27448 2 hours ago

Racket has been able to produce standalone executables for a while now.

gus_massa 2 hours ago

I agree. In 2020 we had to manipulate some Moodle files. I wrote the code in Racket and I sent the ".exe" file to my coworkers, that never knew they were using Racket.

Vedor 2 hours ago

For years, really.

TheGoddessInari 2 hours ago

https://docs.racket-lang.org/guide/exe.html

em-bee 6 hours ago

any time the topic of racket comes up, i wonder if there are any interesting apps i could explore. but all i find is libraries and dev tools: https://awesome-racket.com/

LasEspuelas 5 hours ago

There is this https://remember.defn.io/

You can read the about it here: https://defn.io/2020/01/04/remember-internals/

eru an hour ago

You can ask Claude to write you some.

mono442 4 hours ago

it's an academic language

spike021 44 minutes ago

We used it in the course I had that introduced functional programming. The only memorable thing I can remember writing in it for that class was a topological sort (I believe).

vatsachak 4 hours ago

I've never seen the appeal in schemes other than hot reloadability...

WalterGR 4 hours ago

Homoiconicity.

chowells 3 hours ago

What makes this a desirable feature? From the perspective where local reasoning is the most desirable property a language can have, how does homoiconicity support that?

I honestly am curious. I've seen a few examples presented for it, but they always seem like bad software engineering to me. Where's an example that does something in a cleaner way than alternatives present in other languages while remaining compatible with local reasoning?

gus_massa 2 hours ago

WalterGR 2 hours ago

bjoli 3 hours ago

eru an hour ago

C has homoiconicity: you can represent C source code as C strings.

layer8 2 hours ago

I don’t find it appealing when everything looks the same irrespective of purpose and context.

eru an hour ago

mcbk2142 4 hours ago

Very cool! Always was interested in racket, I will try writing Black Jack in it!

tech_army 4 hours ago

Will definitely try it.

usxr1515 2 hours ago

I've been designing my own small language runtime in Rust (VM + JIT + AOT backends) mostly as a way to actually understand tradeoffs compiler authors make instead of just reading about them. Racket's approach to macros and language-oriented programming is one of the things I keep coming back to as a reference curious how much of that flexibility comes at a real runtime cost vs. being mostly a compile-time abstraction.