2021-06-04 00:50:44	kluk>	How do I start using DynArray from the ocaml command line?
2021-06-04 00:50:51	kluk>	I have already done opam install extlib
2021-06-04 00:51:12	kluk>	I am a newbie at OCaml
2021-06-04 05:18:03	dockerusocamlus>	Hello! I'm minimizing an Alpine-based Docker image with OCaml installed via opam, and I'm trying to understand if I could erase some files to save some space. Basically, trying to understand if they are needed only on special situations, or if that would cause issues for users of the Docker image.
2021-06-04 05:19:46	dockerusocamlus>	For instance, in this image, I have file ~/.opam/<version>/lib/ocaml/expunge, which take 15 MB of space. I don't think I have ever used it, but I don't know if it's internally used by some other OCaml process.
2021-06-04 05:28:12	dockerusocamlus>	I don't have much documentation about it, and grepping ocaml's sources only shows a few occurrences. It seems related to the installation of the OCaml compiler itself, but even after removing it, I'm still able to do a `opam switch create` to install a different compiler, so... I guess it's fine to remove it?
2021-06-04 05:36:13	octachron>	This is a compiler tool which is used to build REPLs. It is also used by utop.
2021-06-04 05:42:54	dockerusocamlus>	Thanks!
2021-06-04 08:10:44	superherointj>	Need some feedback on a minimalistic lwt demo: https://github.com/superherointj/lwt-demo1
2021-06-04 08:38:37	d_bot>	<superherointj> Just solved it. I must be really tired.
2021-06-04 09:49:45	d_bot>	<superherointj> Can anybody point me to a good article/information on incompatible ppx drivers (ppxlib and ocaml-migrate-parsetree)?
2021-06-04 09:49:46	d_bot>	<superherointj> I have read already the saga blog post, but I am missing something.
2021-06-04 09:49:47	d_bot>	<superherointj> I want to build my old project. I'm trying to replicate problem atm on a demo.
2021-06-04 09:50:25	companion_cube>	people are supposed to use ppxlib, that's all I know
2021-06-04 09:51:25	d_bot>	<superherointj> Any example?
2021-06-04 09:51:51	companion_cube>	https://github.com/ocaml-ppx/ppx_deriving I guess?
2021-06-04 09:52:40	d_bot>	<superherointj> Found this:
2021-06-04 09:52:41	d_bot>	<superherointj> https://ppxlib.readthedocs.io/_/downloads/en/stable/pdf/
2021-06-04 09:57:49	d_bot>	<EduardoRFS> Why does OCaml not optimizes this in a noop? Even under flambda and -O3
2021-06-04 09:57:49	d_bot>	<EduardoRFS>
2021-06-04 09:57:51	d_bot>	<EduardoRFS> ```ocaml
2021-06-04 09:57:52	d_bot>	<EduardoRFS> let f (a, b) = (a, b)
2021-06-04 09:57:53	d_bot>	<EduardoRFS> ```
2021-06-04 10:00:07	@adrien>	it returns a new tuple, not the same one
2021-06-04 10:00:37	@adrien>	let x = (1,2);; let f (a, b) = (a, b);; let y = f x;; y == x;;
2021-06-04 10:00:41	d_bot>	<EduardoRFS> the question is why? It would change the `==` behavior but it's already not defined from what I remember
2021-06-04 10:01:06	d_bot>	<EduardoRFS> it behaves differently in bytecode, native and IIRC it's also different in flambda
2021-06-04 10:01:14	companion_cube>	I agree it'd be a valid optim
2021-06-04 10:02:19	d_bot>	<EduardoRFS> This is especiall try for the case of different types and pattern matching but that generates identical data in memory, like
2021-06-04 10:02:20	d_bot>	<EduardoRFS>
2021-06-04 10:02:21	d_bot>	<EduardoRFS> ```ocaml
2021-06-04 10:02:22	d_bot>	<EduardoRFS> type a = | A(int)
2021-06-04 10:02:24	d_bot>	<EduardoRFS> type b = B(int)
2021-06-04 10:02:25	d_bot>	<EduardoRFS> let f = function | A v -> B v
2021-06-04 10:02:26	d_bot>	<EduardoRFS> ```
2021-06-04 10:02:36	@adrien>	I get the same behaviour in native
2021-06-04 10:03:11	@adrien>	and you can do f u = u
2021-06-04 10:03:13	companion_cube>	@eduardors these are only the same by accident though
2021-06-04 10:03:18	companion_cube>	seems far less useful as an optim
2021-06-04 10:03:18	zozozo>	see https://github.com/ocaml/ocaml/pull/8958
2021-06-04 10:03:22	d_bot>	<EduardoRFS> yes but the compiler knows it
2021-06-04 10:03:32	@adrien>	not sure how is the generated code but in that case it's not a new tuple
2021-06-04 10:04:02	zozozo>	there is a PR to do pretty much that (the link I posted above)
2021-06-04 10:04:05	theblatte>	I keep writing functions like `let f ((a,b) as x0) = let a' = g a in let b' = g b in if a == a' && b == b' then x0 else (a', b')`
2021-06-04 10:04:07	d_bot>	<EduardoRFS> in this case yes, but not all cases, I'm not asking about this specific tuple, I'm asking more about identical blocks that are known to be always identical
2021-06-04 10:04:13	companion_cube>	I don't think it's a very useful optimization to see if per chance two different variants of different types happen to have the same binary representation
2021-06-04 10:04:33	companion_cube>	more important stuff is to eliminate temporaries imho
2021-06-04 10:04:41	companion_cube>	like a tuple built just to be deconstructed in the same function
2021-06-04 10:04:45	companion_cube>	(or an option…)
2021-06-04 10:04:53	zozozo>	companion_cube: what do you mean by "temporaries"?
2021-06-04 10:05:05	d_bot>	<EduardoRFS> temporary allocations IIUC
2021-06-04 10:05:06	companion_cube>	data that doesn't escape the current function :p
2021-06-04 10:05:09	zozozo>	companion_cube: ah, well, avoiding these is more or less exactly the job of flambda, ^^
2021-06-04 10:05:11	companion_cube>	(after inlining)
2021-06-04 10:05:12	companion_cube>	yeah I know
2021-06-04 10:05:17	companion_cube>	godspeed to you zozozo 
2021-06-04 10:05:30	zozozo>	^^
2021-06-04 10:05:55	zozozo>	@EduardoRFS : did you look at https://github.com/ocaml/ocaml/pull/8958 ?
2021-06-04 10:07:07	d_bot>	<EduardoRFS> I'm looking on it, the argument of not being predictable is sad, it's a flat allocation reduction, no hidden allocation, not trying to make non efficient code efficient, but trying to make code that is efficient as possible more efficient
2021-06-04 10:07:34	zozozo>	companion_cube: also, note that sometimes, because of type subtleties, you need to write the "identity" function, as a pattern match that then reconstructs exactly the same value, but with a slightly different type (thing GADTs), in such cases, being able to detect that a switch returns exactly its argument, is a nice improvements, and you can't really write it differently because of the types
2021-06-04 10:07:36	@adrien>	well, as theblatte said, the "as" construct should help for that case
2021-06-04 10:08:04	d_bot>	<EduardoRFS> that's exactly the case zozozo, for a lot of code in ocaml-migrate-types
2021-06-04 10:08:11	theblatte>	zozozo: yes!
2021-06-04 10:08:19	zozozo>	the advantage of the PR I linked is that it can trigger in cases where one cannot write code using "as"
2021-06-04 10:08:27	theblatte>	much sad when that happens
2021-06-04 10:08:30	d_bot>	<EduardoRFS> "as"?
2021-06-04 10:08:53	zozozo>	@EduardoRFS : `let f ((a, b) as pair) = pair`
2021-06-04 10:09:13	d_bot>	<EduardoRFS> oh but that works only for structural types
2021-06-04 10:09:21	companion_cube>	zozozo: good argument against GADTs ;)
2021-06-04 10:09:34	d_bot>	<EduardoRFS> companion_cube loves GADTs
2021-06-04 10:09:42	companion_cube>	heh, in small doses
2021-06-04 10:09:47	theblatte>	companion_cube: no need for GADTs! https://github.com/facebook/infer/blob/cfed4c4fa0c99ab1f42683bb92df76c8c8434e79/infer/src/pulse/PulseSummary.ml#L56
2021-06-04 10:10:03	olle>	as?
2021-06-04 10:10:06	olle>	new keyword?
2021-06-04 10:10:13	companion_cube>	wait, theblatte, why
2021-06-04 10:10:14	theblatte>	eg phantom type parameters
2021-06-04 10:10:18	companion_cube>	ah yes
2021-06-04 10:10:29	companion_cube>	it's unfortunate
2021-06-04 10:10:34	theblatte>	(in my case not phantom but "phantom" because it doesn't show up in some of the variants)
2021-06-04 10:10:37	companion_cube>	but it's the same constructors in this case.
2021-06-04 10:10:38	zozozo>	companion_cube: gadts are useful *sometimes*
2021-06-04 10:10:40	d_bot>	<EduardoRFS> I wonder if #8958 would be better as lambda layer
2021-06-04 10:10:44	d_bot>	<EduardoRFS> but tempting to rebase it ;/
2021-06-04 10:11:25	zozozo>	@EduardoRFS : the problem is that if you do that at lambda level, you miss out on situations where it happens after some inlining/simplification
2021-06-04 10:11:47	d_bot>	<EduardoRFS> yeah but you ensure same behavior between all backends
2021-06-04 10:11:50	zozozo>	(also, the code of lambda simplifications is quite a mess from what I hear)
2021-06-04 10:12:33	theblatte>	companion_cube: same constructors: yes, personally I would only care about preserving physical equality when the objects are actually equal but ymmv
2021-06-04 10:12:34	zozozo>	well.. there is now a pass specifically designed to implement optimizations, so why not use it ?
2021-06-04 10:13:05	theblatte>	I've seen several examples where it would have a material effect on perf
2021-06-04 10:13:08	d_bot>	<EduardoRFS> But the pass should not change behavior of code unless it provides a fallback, this is how I see most of it
2021-06-04 10:13:13	d_bot>	<EduardoRFS> maybe Sys.opaque_identity would ignore it
2021-06-04 10:13:32	d_bot>	<EduardoRFS> can we deprecate ==? That seems like a better idea overall
2021-06-04 10:13:34	companion_cube>	zozozo: because it only works for native?
2021-06-04 10:13:41	companion_cube>	ahahah 
2021-06-04 10:13:47	companion_cube>	removing == kills perf for other programs
2021-06-04 10:14:01	theblatte>	#8958 ftw, I didn't know there'd been such a PR in flight for such a long time
2021-06-04 10:14:04	zozozo>	companion_cube: well, bytecode is pretty much meant to not care about performance, so from that point of view it's not unreasonable
2021-06-04 10:14:05	d_bot>	<EduardoRFS> not removing it, deprecating it, keep it under Obj.xx
2021-06-04 10:14:34	theblatte>	== is an important part of the language, not an extension
2021-06-04 10:14:41	zozozo>	the *good* solution would be to change the bytecode generation to use the result of flambda
2021-06-04 10:14:56	zozozo>	the semantics of "==" is largely not officially specified
2021-06-04 10:14:56	d_bot>	<EduardoRFS> NAH
2021-06-04 10:15:10	theblatte>	but not a bad idea to not give it such an easily-confused name :p eg use "phys_equal" instead
2021-06-04 10:15:12	zozozo>	and for any non-mutable record, there are next to no guarantees about "=="
2021-06-04 10:15:26	d_bot>	<EduardoRFS> unless we had a blazing fast flambda pass, bytecode is so fast right now
2021-06-04 10:16:22	d_bot>	<EduardoRFS> == is not exactly part of the language in many ways, and it's known to behave differently depending on the backend which should never happen for a specified feature of the language
2021-06-04 10:16:30	zozozo>	@EduardoRFS: are you talking about compilation time or runtime of the compild program ?
2021-06-04 10:16:35	d_bot>	<EduardoRFS> compilation time
2021-06-04 10:16:36	companion_cube>	zozozo: I wish I could agree
2021-06-04 10:16:40	companion_cube>	but some of us are stuck with bytecode
2021-06-04 10:16:45	d_bot>	<EduardoRFS> bytecode is slow in runtime, really slow
2021-06-04 10:16:46	companion_cube>	because that's the only official toplevel for now
2021-06-04 10:17:10	d_bot>	<EduardoRFS> but bytecode generated from flambda would still work with the toplevel
2021-06-04 10:17:16	zozozo>	companion_cube: yeah, but sometimes with others in my team, we talk about making it so that bytecode is generated after the flambda pass, which would solve all problems (if we can make it work)
2021-06-04 10:17:21	companion_cube>	sure
2021-06-04 10:17:36	companion_cube>	I mean in the future maybe we'll also have a JIT
2021-06-04 10:17:42	d_bot>	<EduardoRFS> there is any plan on deprecating closure middle end?
2021-06-04 10:17:45	companion_cube>	but for now it's not like there's a choice, and there's basically 0 optims on bytecode
2021-06-04 10:17:47	companion_cube>	which… ugh
2021-06-04 10:19:26	d_bot>	<dinosaure> it remmembers me one time when people compared ocsigenserver and http servers and used the bytecode version accidentally and say, OCaml is so bad
2021-06-04 10:19:34	companion_cube>	:D
2021-06-04 10:19:38	d_bot>	<EduardoRFS> D:
2021-06-04 10:19:49	companion_cube>	or even using dune without --profile=release
2021-06-04 10:19:53	companion_cube>	bye bye optims
2021-06-04 10:19:58	d_bot>	<EduardoRFS> TEZOS IS RUNNING WITHOUT PROFILE=RELEASE
2021-06-04 10:20:25	d_bot>	<EduardoRFS> even worse it is benchmarked without profile=release
2021-06-04 10:20:33	companion_cube>	hu, weirder
2021-06-04 10:21:18	zozozo>	well, if the switch is not using flambda, I don't think the difference is that important between the dev and release profiles
2021-06-04 10:22:34	companion_cube>	err, you still have a bit of cross module inlining, don't you?
2021-06-04 10:22:39	companion_cube>	with normal ocamlopt
2021-06-04 10:22:54	zozozo>	I'm not sure
2021-06-04 10:22:55	d_bot>	<EduardoRFS> yeah it makes difference, I benchmarked it, around 30% boost on some smart contracts
2021-06-04 10:23:06	d_bot>	<EduardoRFS> dune without profile=release runs under -opaque
2021-06-04 10:23:10	companion_cube>	I think it does, including for stuff like externals
2021-06-04 10:23:16	companion_cube>	exactly
2021-06-04 10:23:25	companion_cube>	--profile=release brings you back to normal behavior
2021-06-04 10:23:26	zozozo>	I think (but I'm not sure) the only thing cross-inlined would be externals, but those are in the .mlis so no need for cross-optimization actually
2021-06-04 10:23:30	d_bot>	<EduardoRFS> externals rely on the interface, so it doesn't depend on profile=release
2021-06-04 10:23:50	companion_cube>	zozozo: but the .cmx ?
2021-06-04 10:24:00	theblatte>	is profile=release different than passing -O3 to ocamlopt??
2021-06-04 10:24:05	zozozo>	ah, maybe the small functions that closure unconditionally inline are inliend cross-modules by vanilla ocamlopt
2021-06-04 10:24:17	d_bot>	<EduardoRFS> it is, because without profile=release you're under -opaque
2021-06-04 10:24:30	theblatte>	whaaaat
2021-06-04 10:24:40	theblatte>	:o
2021-06-04 10:24:44	d_bot>	<EduardoRFS> that's the only way to achieve blazing fast build speed
2021-06-04 10:24:53	companion_cube>	zozozo: the functions marked "inline" in .cmx files
2021-06-04 10:24:56	d_bot>	<EduardoRFS> yup, small functions like having `Module.equal` are not inlined and Module.equal a lot of times is literally a single cnstruction
2021-06-04 10:25:09	theblatte>	blazing fast = 6x slower than without -O3 ^^
2021-06-04 10:25:11	companion_cube>	that's what I was talking about
2021-06-04 10:25:21	zozozo>	companion_cube: indeed, ^^
2021-06-04 10:25:30	companion_cube>	so it can make a big difference :)
2021-06-04 10:25:35	companion_cube>	even without flambda
2021-06-04 10:25:45	theblatte>	ohhh, recently-ish we noticed marking some functor arguments as [@inline] made a big difference
2021-06-04 10:25:52	companion_cube>	:D 
2021-06-04 10:25:59	zozozo>	that's not surprising
2021-06-04 10:26:04	theblatte>	is that sort of thing (adding @inline) not needed with flambda + release profile?
2021-06-04 10:26:25	theblatte>	or is that independent?
2021-06-04 10:26:26	companion_cube>	it still gives you better control
2021-06-04 10:26:34	zozozo>	iirc, flambda tries as much as possibvle to inline functor applicaiton that are at toplevel, so you shouldn't need the annotations in that particular case
2021-06-04 10:26:51	companion_cube>	do a lot of people use flambda1  in production?!
2021-06-04 10:26:59	zozozo>	companion_cube: jane street i guess ?
2021-06-04 10:27:07	companion_cube>	ahah maybe they have enough RAM
2021-06-04 10:27:16	zozozo>	also, the binary release of dolmen is now compiled with flambda, :D
2021-06-04 10:27:18	companion_cube>	I stopped using it years ago
2021-06-04 10:27:18	theblatte>	infer is 30% faster with flambda, so you bet
2021-06-04 10:27:32	companion_cube>	wow
2021-06-04 10:27:37	companion_cube>	well can't wait for flambda2
2021-06-04 10:28:01	companion_cube>	anyway, the point of --profile=release is to tell dune to not block optimizations, it doesn't enable new ones
2021-06-04 10:28:05	companion_cube>	for that you can use ocamlopt_flags
2021-06-04 10:28:13	d_bot>	<EduardoRFS> tezos is another 20% faster on flambda
2021-06-04 10:28:15	zozozo>	we're trying very hard on making it so that flambda2 is as fast as possible, but it's hard sometimes
2021-06-04 10:28:27	companion_cube>	zozozo: it's not just a question of "fast"
2021-06-04 10:28:35	companion_cube>	it's also "not gobble up RAM on bad cases"
2021-06-04 10:28:38	theblatte>	yes but I'm trying to understand if adding --profile=release will make a difference
2021-06-04 10:28:51	theblatte>	I'll try that
2021-06-04 10:29:01	companion_cube>	so, -p foo already switches to release mode
2021-06-04 10:29:12	companion_cube>	it's only if you use `dune build @all` and that kind of stuff that it matters
2021-06-04 10:29:21	zozozo>	companion_cube: right, can you send me (if you recall), the packages that were not working 'or taking ut too much RAM) ?
2021-06-04 10:29:24	companion_cube>	it makes compilation slower (removes -opaque) but enables optimization
2021-06-04 10:29:27	companion_cube>	zozozo: at least dose3 
2021-06-04 10:29:30	companion_cube>	that was the blocker
2021-06-04 10:29:32	zozozo>	so that we can at least try and see what happens with flamdba2
2021-06-04 10:29:32	companion_cube>	and camlp4
2021-06-04 10:29:35	d_bot>	<EduardoRFS> even the new dose3?
2021-06-04 10:29:52	d_bot>	<EduardoRFS> dose3 6 changed quite a bit of stuff, even parmap they're using now
2021-06-04 10:30:34	theblatte>	companion_cube: we do "dune build infer.exe"
2021-06-04 10:31:29	companion_cube>	lol
2021-06-04 10:31:39	companion_cube>	yeah you need the flag
2021-06-04 10:31:54	companion_cube>	idk about dose3 6
2021-06-04 10:32:01	companion_cube>	I stopped trying flambda a while ago
2021-06-04 10:32:17	companion_cube>	using too much ram is a big problem imho
2021-06-04 10:32:45	d_bot>	<EduardoRFS> that seems weird, flambda reduces the number of allocations considerably
2021-06-04 10:33:30	companion_cube>	per module
2021-06-04 10:33:38	companion_cube>	with this you might also gain cross module
2021-06-04 10:33:54	theblatte>	ah I thought you meant too much ram used during compilation :)
2021-06-04 10:34:09	companion_cube>	that's what I meant yes
2021-06-04 10:34:11	companion_cube>	sorry
2021-06-04 10:34:18	companion_cube>	but theblatte, try the flag :p
2021-06-04 10:34:26	d_bot>	<EduardoRFS> yeah makes sense
2021-06-04 10:34:29	theblatte>	companion_cube: I am!!
2021-06-04 10:34:30	companion_cube>	and also, make sure .cmx are installed for all libraries
2021-06-04 10:34:52	d_bot>	<EduardoRFS> do we have an idea on what leads flambda to use so much memory?
2021-06-04 10:34:57	theblatte>	companion_cube: how?
2021-06-04 10:35:14	companion_cube>	well most should do it if they use dune
2021-06-04 10:35:25	d_bot>	<ggole> Is there any info on flambda2 floating around yet?
2021-06-04 10:35:36	companion_cube>	there's zozozo's brain
2021-06-04 10:35:40	companion_cube>	although it's not floating
2021-06-04 10:39:04	d_bot>	<dinosaure> technically, his brain is floating in his skull
2021-06-04 10:39:15	companion_cube>	he might be a robot
2021-06-04 10:39:17	companion_cube>	can't be sure
2021-06-04 10:39:27	d_bot>	<EduardoRFS> if he is doing flambda2 he is a robot
2021-06-04 10:40:07	zozozo>	right, I can try and answer questions about flambda2
2021-06-04 10:40:17	zozozo>	since I'm working on it, ^^
2021-06-04 10:41:07	companion_cube>	it'll be the default if it works well enough, right?
2021-06-04 10:41:53	zozozo>	that's the plan
2021-06-04 10:43:01	companion_cube>	🤞
2021-06-04 10:43:57	d_bot>	<ggole> Hmm, I'm not sure I know enough about it to ask good questions
2021-06-04 10:45:07	d_bot>	<ggole> Although maybe "what was not adequate about the first flambda design" is an obvious one
2021-06-04 10:45:29	theblatte>	companion_cube: ah, but actually we never use dune default profiles, we do --profile=opt (or dev). There's no -opaque in the build logs
2021-06-04 10:45:41	companion_cube>	ah, I see
2021-06-04 10:45:47	theblatte>	phew :)
2021-06-04 10:45:49	companion_cube>	(wait, there's a profile=opt??)
2021-06-04 10:46:01	theblatte>	you can name your profile however you want :p
2021-06-04 10:46:40	zozozo>	@ggole: basically, flambda2 now uses a CPS representation of source code, which is very useful (whereas flambda1 had an ANF representation iirc)
2021-06-04 10:46:40	theblatte>	then we have (env (opt (ocamlopt_flags (:standard -O3))), etc.
2021-06-04 10:47:35	theblatte>	maybe we should have -opaque for profile=dev though!
2021-06-04 10:47:52	d_bot>	<EduardoRFS> wondering, when the optimization mentioned in 8958 may be triggered after inlining?
2021-06-04 10:48:19	d_bot>	<EduardoRFS> It would be weird if flambda allocated two identical temporary blocks
2021-06-04 10:48:30	d_bot>	<Drup> I also have a question on flambda 2.0
2021-06-04 10:48:37	d_bot>	<ggole> @guigui CPS is an interesting direction. It used to be the IL style of choice, but seems to have gone right out of favour.
2021-06-04 10:49:04	zozozo>	Drup: fire away, ^^
2021-06-04 10:49:07	d_bot>	<Drup> Do you (the flambda team) intend to keep working on it instead of instantly decide to shoot the for moon and work on flambda 3.0 ?
2021-06-04 10:49:36	companion_cube>	lolol
2021-06-04 10:49:39	companion_cube>	I could say the same of ppx
2021-06-04 10:49:44	zozozo>	Drup: the plan is to continue working on flambda2
2021-06-04 10:50:14	d_bot>	<ggole> Although people who use ANF seem to have discovered the need for very continuation-like constructs with join points
2021-06-04 10:50:17	zozozo>	basically, doing flambda1 gave the team (note that this was before I joined) some insights about how to do and not to do some things
2021-06-04 10:50:17	d_bot>	<Drup> (you don't have to answer it, it's friday evening, and I know you don't really have a sway on this all that much)
2021-06-04 10:50:50	zozozo>	Drup: indeed, but I'm right now in a conference call with Pierre so I can ask him, ^^
2021-06-04 10:51:02	d_bot>	<Drup> Say hello from me :p
2021-06-04 10:51:22	zozozo>	Drup: he says hello to you too
2021-06-04 10:52:18	theblatte>	hi pchambart :)
2021-06-04 10:52:48	companion_cube>	coucou to him
2021-06-04 10:52:58	d_bot>	<Drup> but yeah, flambda in general is a bit moonshot infused sometimes. I understand why (it's much more fun to work on "The Perfect IR") but it's a bit infuriating.
2021-06-04 10:53:28	companion_cube>	like multicore has been for a while, too
2021-06-04 10:53:31	companion_cube>	or even opam 2.1
2021-06-04 10:53:36	companion_cube>	seems like a common theme in OCaml :p
2021-06-04 10:53:37	theblatte>	companion_cube: alright so something good still came out of that: compiling with -opaqe turns a 50s full build into a 40s one \o/ and I assume it's even better for incremental build?
2021-06-04 10:53:42	zozozo>	yeah, but now with flambda2 we should have a good enough IR to do what we want and need
2021-06-04 10:54:11	companion_cube>	theblatte: err it's faster builds, but slower code, yes
2021-06-04 10:54:12	d_bot>	<Drup> let's hope so
2021-06-04 10:54:34	theblatte>	companion_cube: it's for "dev" builds
2021-06-04 10:54:49	companion_cube>	then yes
2021-06-04 10:55:07	companion_cube>	with -opaque you have fully separate compilation
2021-06-04 10:55:24	theblatte>	I was wondering why dune was doing so much work on incremental compilation ^^
2021-06-04 10:55:31	theblatte>	thanks!
2021-06-04 10:56:35	d_bot>	<Drup> (I though dune already added `-opaque` for dev builds)
2021-06-04 10:57:05	d_bot>	<ggole> @guigui what was difficult before that's easy now?
2021-06-04 10:57:06	companion_cube>	seems like theblatte has his own profiles
2021-06-04 10:57:37	companion_cube>	zozozo: so in CPS, do you have 2 "kinds" of function calls? normal and continuations?
2021-06-04 10:57:42	companion_cube>	to make sure there's no new closures?
2021-06-04 10:57:53	d_bot>	<Drup> That doesn't seem very smart if those are less though-out than the normal ones :3
2021-06-04 10:57:56	theblatte>	dune profiles have... weird defaults
2021-06-04 10:58:24	theblatte>	fair enough :p
2021-06-04 10:59:06	zozozo>	companion_cube: continuations in flambda2 are more along the lines of static jumps
2021-06-04 10:59:12	companion_cube>	cool
2021-06-04 10:59:33	companion_cube>	zozozo: please stop delaying the PR for ocaml.org 
2021-06-04 10:59:33	companion_cube>	plz
2021-06-04 11:00:48	zozozo>	sorry, ^^
2021-06-04 11:00:57	companion_cube>	why does a PR against a fracking website take a full week to be merged anyway
2021-06-04 11:01:29	zozozo>	right, that's a problem
2021-06-04 11:02:22	companion_cube>	if you want the website to go stale because no one opens a PR to update it, that's the best way to go
2021-06-04 11:02:38	octachron>	companion_cube, because there is noone clearly responsible? My commit right is normally mostly for OCaml releases
2021-06-04 11:03:07	companion_cube>	is Anil trying to do too many things? :p
2021-06-04 11:03:21	companion_cube>	definitely not blaming you octachron 
2021-06-04 11:04:36	companion_cube>	just  annoyed that this, which should have taken literally 5 minutes, is taking a week
2021-06-04 11:04:41	theblatte>	interesting, -opaque seems to make no difference for incremental compilation, only for full compilation
2021-06-04 11:04:46	companion_cube>	during which the information on the website is misleading
2021-06-04 11:05:14	companion_cube>	theblatte: try modifying a file deep in the dep graph, but only the implementation, not the interface
2021-06-04 11:05:22	theblatte>	that's what I tried
2021-06-04 11:05:36	companion_cube>	hu
2021-06-04 11:06:25	theblatte>	humm, there's a leftover -opaque in the logs, my experiment must have gone wrong, sorry, digging in further
2021-06-04 11:11:27	d_bot>	<EduardoRFS> theblatte: also opaque allows to build strictly against cmi which leads to better parallelism if you're using mli well
2021-06-04 11:12:30	d_bot>	<EduardoRFS> so opaque should definitely matter for incremental as without it you need to rebuilt the full tree if any module changes
2021-06-04 11:12:36	d_bot>	<EduardoRFS> maybe dune doesn't have this implemented?
2021-06-04 11:12:48	d_bot>	<EduardoRFS> @rgrinberg any idea here?
2021-06-04 11:13:00	theblatte>	I think because we use the "dev" name for our profile -opaque was already being passed!
2021-06-04 11:13:48	theblatte>	even though we override (flags ...)
2021-06-04 11:13:53	theblatte>	but not ocamlopt_flags
2021-06-04 11:15:11	octachron>	companion_cube, anyway my week ended 15 minutes ago, so the PR is merged.
2021-06-04 11:16:16	theblatte>	and we still see a win for the full build by forcing -opaque because it passes it in a bunch of places where dune doesn't by default
2021-06-04 11:16:58	theblatte>	looks like that's when building the entire libraries' .cmx
2021-06-04 11:17:21	@adrien>	octachron: thanks :)
2021-06-04 11:17:46	theblatte>	so, hmmm, *shrug*
2021-06-04 11:39:10	companion_cube>	octachron: 😂 thank you
2021-06-04 11:43:12	companion_cube>	and the website is updated already, nice
2021-06-04 11:46:07	companion_cube>	"variant constructor unboxing" that's nice
2021-06-04 11:46:16	companion_cube>	didn't we discuss it here recently? 
2021-06-04 11:46:21	companion_cube>	 perhaps about bitvectors
2021-06-04 11:51:05	olle>	oooooh
2021-06-04 13:58:46	zozozo>	@ggole : sorry for the delay, basically, control flow manipulation is much easier in cps form, also inlining a function's body is tricky to do in ANF (and can be exponential in the worst case if you need to ensure the result if in strict ANF)
2021-06-04 13:59:23	companion_cube>	coudl you post a snippet of a tiny CPS AST? :p
2021-06-04 13:59:39	companion_cube>	sth where we could see let, application, and like a primitive like + ?
2021-06-04 13:59:44	zozozo>	sure
2021-06-04 13:59:56	companion_cube>	👍
2021-06-04 14:00:08	companion_cube>	I want to see how the continuations are represented
2021-06-04 14:07:32	zozozo>	https://gist.github.com/Gbury/7a02a35cb4906914fa351183490f11b2
2021-06-04 14:07:44	zozozo>	basically, a continuation is a (unique) integer
2021-06-04 14:08:05	zozozo>	companion_cube: ^
2021-06-04 14:09:06	companion_cube>	so, apply_cont is where you jump
2021-06-04 14:09:09	zozozo>	yup
2021-06-04 14:09:29	zozozo>	also, after a function call (i.e. Apply_expr), you call the given continuation with the return value of the function call
2021-06-04 14:09:35	companion_cube>	and why is there 2 let?
2021-06-04 14:09:42	companion_cube>	yeah
2021-06-04 14:09:49	companion_cube>	and you call the function on already computed arguments
2021-06-04 14:09:59	zozozo>	you can bind continuations, and regular expressions
2021-06-04 14:10:37	companion_cube>	hmmm
2021-06-04 14:10:54	companion_cube>	I mean, Let_expr makes sense, it's a local definition, ok
2021-06-04 14:11:00	companion_cube>	but what's the "handler" in Let_cont?
2021-06-04 14:11:00	zozozo>	yup
2021-06-04 14:11:07	zozozo>	the code of the continuation
2021-06-04 14:11:17	companion_cube>	oh shit ok
2021-06-04 14:11:17	zozozo>	let_cont k args = handler in body
2021-06-04 14:11:22	companion_cube>	nice
2021-06-04 14:11:43	zozozo>	note that continuations are local to a function's body and cannot escape
2021-06-04 14:11:44	companion_cube>	so patmatch could also create such expressions, for example
2021-06-04 14:11:55	zozozo>	since continuations are not regular value (i.e. simples or named)
2021-06-04 14:11:55	companion_cube>	with explicit sharing and everything
2021-06-04 14:12:02	zozozo>	yes
2021-06-04 14:12:29	companion_cube>	(I imagine switch could also have a default case)
2021-06-04 14:12:49	zozozo>	in this case no, the switch has no default case
2021-06-04 14:12:56	zozozo>	it simplifies some things
2021-06-04 14:13:07	zozozo>	but in theory it could
2021-06-04 14:13:08	companion_cube>	even in flambda2?
2021-06-04 14:13:17	companion_cube>	I guess since you can share continuations, it's ok
2021-06-04 14:13:24	zozozo>	it's just that having no default case means the code is much more regular
2021-06-04 14:13:29	zozozo>	you can fold on the arms of the switch
2021-06-04 14:13:41	zozozo>	and not have to specifically treat the default case
2021-06-04 14:15:30	companion_cube>	heh, fair enough
2021-06-04 14:16:03	companion_cube>	I think the insight that continuations are not values, is sth I didn't realize
2021-06-04 14:16:05	companion_cube>	so thank you! :)
2021-06-04 14:16:27	zozozo>	no problem, ^^
2021-06-04 14:30:12	d_bot>	<ggole> zozozo: hmm, that's actually pretty close to what I expected. Thanks for taking the time to write it up.
2021-06-04 14:33:07	d_bot>	<ggole> When I tried CPS ILs I found it difficult to perform what should be simple transformations like commuting `case` expressions, but perhaps my approach was too naive.
2021-06-04 14:37:04	zozozo>	@ggole : well, commuting switches would be quite complicated indeed (and isn't done currently in flambda2)
2021-06-04 14:38:59	d_bot>	<ggole> That's one benefit of a more lambda-calculus like IL, it's quite easy to do context-directed optimisations (of which commuting is probably the most significant)
2021-06-04 14:39:37	zozozo>	yeah, but then again, I don't think commuting is really something that we want to do in flambda2
2021-06-04 14:39:39	d_bot>	<ggole> But there are downsides with scope
2021-06-04 14:39:55	d_bot>	<colin> will flambda2 carry through to faithful CPS compilation or what
2021-06-04 14:40:21	zozozo>	@colin : I'm not sure what you mean ?
2021-06-04 14:41:00	d_bot>	<ggole> SML/NJ style CPS all the way? Seems unlikely.
2021-06-04 14:41:03	d_bot>	<colin> I've seen compilers that use CPS as an IR yet blast to something slightly different to compile to something that still uses a runtime stack
2021-06-04 14:41:22	d_bot>	<colin> Yeah, I don't think SML/NJ or MLton can be described as using CPS to much of an extent nowadays tbh
2021-06-04 14:41:57	d_bot>	<ggole> I thought SML/NJ still used that for their `Cont` implementation
2021-06-04 14:41:57	zozozo>	ah well, the flambda IR is in CPS, but there will be no change to the other IR of the compiler, so that's that, ^^
2021-06-04 14:43:13	d_bot>	<colin> is the Apply_cont constructor in this cps.ml file representing "contificated"/static continuations?
2021-06-04 14:43:43	zozozo>	yeah, it represents static continuations bound previously by a Let_cont
2021-06-04 14:43:59	d_bot>	<colin> interesting, I've only ever seen the IR presented in Appel's CwC book
2021-06-04 14:44:30	d_bot>	<ggole> There's a nice paper on an CPS IR a bit like this that you might be interested in
2021-06-04 14:44:36	d_bot>	<colin> is it by Kennedy
2021-06-04 14:44:42	d_bot>	<ggole> Yeah
2021-06-04 14:44:56	d_bot>	<colin> yeah, I've seen that as well actually, it's the one most people seem to go with I think
2021-06-04 14:45:17	d_bot>	<ggole> Makes a lot of sense if you aren't supporting call/cc
2021-06-04 14:45:18	companion_cube>	zozozo: what comes after flambda? something with a control flow graph already?
2021-06-04 14:45:36	zozozo>	companion_cube: after flambda, it's cmm
2021-06-04 14:46:07	d_bot>	<colin> been a while since I've toyed with CPSing compilers because very few go the full mile with the whole "no runtime stack" - they go the chicken route and use it as a GC nursery because they can't get their C compiler to do the strict (tail) call -> jumps that CPS requires and LLVM certainly can't handle CPS so you're just stuck writing your own back-end each time
2021-06-04 14:46:17	zozozo>	(fun factoid: cmm quite literraly means C minus minus, :p )
2021-06-04 14:46:56	d_bot>	<ggole> If the continuations are second class as in this example, then you can probably linearise to SSA fairly successfully
2021-06-04 14:47:25	companion_cube>	hmm so cmm still has function calls and expressions, but no types, right?
2021-06-04 14:47:33	d_bot>	<colin> I just think going from ANF -> LLVM (SSA) is simpler
2021-06-04 14:47:41	d_bot>	<ggole> Although there's the usual complications of closure conversion and whatnot because LLVM is first order
2021-06-04 14:48:10	d_bot>	<colin> Oleg seems to have some strong views on actually doing faithful compilation of CPS as well, along the lines of "whole-program continuations are never useful" and uh "the garbage collector doesn't like this" etc. paraphrasing (perhaps inaccurately) here
2021-06-04 14:48:21	zozozo>	companion_cube: cmm has very minimal types (basically it says whether a value can/should be scanned)
2021-06-04 14:48:39	d_bot>	<ggole> Well, CPS as a compiler IL is a different storly to exposing continuations reified as functions
2021-06-04 14:48:42	companion_cube>	yeah, that's not typing ;)
2021-06-04 14:49:20	companion_cube>	but there you eliminate continuations again, right? towards some sort of static jump, like local exceptions?
2021-06-04 14:49:27	zozozo>	yup
2021-06-04 14:49:38	zozozo>	cmm has static jumps and flambda continuations maps perfectly to that
2021-06-04 14:49:50	zozozo>	(ofc continuations that are used exactly once can be inlined)
2021-06-04 14:50:23	companion_cube>	right
2021-06-04 14:50:32	d_bot>	<ggole> Either a return or a jump
2021-06-04 14:50:36	d_bot>	<colin> this discussion is urging me to actually go and read Shivers' k-CFA stuff since I've always just avoided any real detail/proposed benefit of program transformations in CPS
2021-06-04 14:50:39	companion_cube>	you can still use static jumps for patmathc and stuff
2021-06-04 14:50:54	d_bot>	<ggole> Or maybe an exception handler if double-barrelled CPS
2021-06-04 14:51:18	zozozo>	flambda actually has double-barrelled CPS
2021-06-04 14:51:22	zozozo>	(flambda2)
2021-06-04 14:51:47	d_bot>	<ggole> That makes sense, rather than duplicating all of the control constructs
2021-06-04 14:51:51	d_bot>	<ggole> And optims on them
2021-06-04 14:52:40	d_bot>	<colin> what's double-barrelled, just doing the CPS twice?
2021-06-04 14:52:58	companion_cube>	wait
2021-06-04 14:53:03	companion_cube>	does the second handler also work for effects?
2021-06-04 14:53:10	companion_cube>	or wolud there be a third handler?
2021-06-04 14:53:11	d_bot>	<ggole> Along with the usual return continuation you pass another continuation which is the error/exn path
2021-06-04 14:53:42	d_bot>	<colin> ah
2021-06-04 14:54:19	zozozo>	companion_cube: effects as in algebraic effects (cf multicore) ?
2021-06-04 14:54:29	companion_cube>	yes
2021-06-04 14:54:34	companion_cube>	runtime effects anyway
2021-06-04 14:54:38	companion_cube>	the one shot continuations :)
2021-06-04 14:54:43	zozozo>	that's a very good question
2021-06-04 14:55:21	companion_cube>	I think exceptions will just be another effect, except in the type system, so you can probably only have 2
2021-06-04 14:55:22	d_bot>	<colin> who funds OCamlPro? INRIA? Jane Street? or is it its own company
2021-06-04 14:57:27	d_bot>	<Christophe> I have a question about the change log of 4.13. The change "type check x |> f and f @@ x as (f x) ` is marked as breaking change. What are the consequences of that change actually? (sorry for interrupting a very interesting conversation)
2021-06-04 14:59:15	companion_cube>	it might change a few things in a subtle way
2021-06-04 14:59:22	companion_cube>	like `f x` can be `f ?a ?b x`
2021-06-04 14:59:26	companion_cube>	if f has optional arguments
2021-06-04 14:59:43	zozozo>	@colin : OCamlPro is its own company, and janestreet is one client of ocamlpro
2021-06-04 15:00:51	d_bot>	<colin> Ah, I see, I was looking at compiler jobs at Jane Street (wishful thinking) but now they don't seem like they'd be as interesting as this flambda2 stuff (unless there's some ties between both companies)
2021-06-04 15:01:19	d_bot>	<Christophe> Ah yes, I didn't think of optional arguments, thanks!
2021-06-04 15:01:37	companion_cube>	aren't they funding flambda2? :D
2021-06-04 15:01:37	zozozo>	@colin : well, the work on flambda2 is funded by JaneStreet, ^^
2021-06-04 15:41:47	d_bot>	<EduardoRFS> type check of `x |> f` as `f x` is something I was not expecting but I really appreciate
2021-06-04 15:42:00	d_bot>	<EduardoRFS> now we need to type check `let x = y` in the opposite order
2021-06-04 15:43:25	d_bot>	<EduardoRFS> can we implement this kind of subtyping or would it be unsound?
2021-06-04 15:43:26	d_bot>	<EduardoRFS> ```ocaml
2021-06-04 15:43:27	d_bot>	<EduardoRFS> module X : sig
2021-06-04 15:43:28	d_bot>	<EduardoRFS>   type 'a t = private 'a
2021-06-04 15:43:30	d_bot>	<EduardoRFS> end = struct
2021-06-04 15:43:31	d_bot>	<EduardoRFS>   type 'a t = 'a
2021-06-04 15:43:32	d_bot>	<EduardoRFS> end
2021-06-04 15:43:34	d_bot>	<EduardoRFS> let add (a : int X.t) (b : int) = a + b
2021-06-04 15:43:35	d_bot>	<EduardoRFS> ```
2021-06-04 16:03:27	d_bot>	<octachron> This is already implemented, with an explicit coercion as usual: `let add a b = (a:int X.t:>int) + b`
2021-06-04 19:56:48	hackinghorn>	hi
2021-06-04 19:57:03	hackinghorn>	how do I run commands like ls for linux in ocaml?
2021-06-04 19:59:38	dh`>	there's a binding for system() somewhere
2021-06-04 19:59:40	hackinghorn>	oh, fileutils work
2021-06-04 19:59:56	hackinghorn>	got it, thanks
2021-06-04 23:15:51	d_bot>	<EduardoRFS> Why not implicit?
2021-06-04 23:20:48	companion_cube>	There are no implicit coercions in ocaml 
2021-06-04 23:51:53	d_bot>	<dj charlie> 👀 nice to see the stdlib increasingly fleshed out feels good
2021-06-05 00:39:14	companion_cube>	like what?
2021-06-05 00:57:05	d_bot>	<dj charlie> like fold_left and fold_right with the strings
2021-06-05 00:57:12	d_bot>	<dj charlie> the math functions for floats
2021-06-05 01:05:15	companion_cube>	Lolol ok
2021-06-05 01:05:33	companion_cube>	Fold on string, heh? 
2021-06-05 01:05:43	companion_cube>	Forgot that that wasn't there
2021-06-05 01:06:10	d_bot>	<dj charlie> hey guy who wrote his own stdlib
2021-06-05 01:06:13	d_bot>	<dj charlie> it's pretty cool to me ok?
2021-06-05 07:50:23	companion_cube>	:D it is, it is
2021-06-05 09:57:02	tane>	howdy! found the way
2021-06-05 11:46:29	d_bot>	<giga_08> anyone familiar with ocaml verification? termination in particular
2021-06-05 12:03:08	d_bot>	<darrenldl> small code or large projects?
2021-06-05 12:41:30	d_bot>	<giga_08> small code
2021-06-05 13:02:29	companion_cube>	@giga_08 you could give a look at try.imandra.ai (it's proprietary but termination checking is def. sth interesting)
2021-06-05 18:18:14	d_bot>	<TheSkeward> learning ocaml and I occasionally giggle to myself because "O Caml! My Camel!" will pop into my head like a line from some sort of desert-themed walt whitman poem
2021-06-05 18:19:38	companion_cube>	`my $camel` sounds more like perl, tbh
2021-06-05 18:21:20	d_bot>	<TheSkeward> perls before swine
2021-06-05 23:22:45	kluk>	how do I start using DynArray? I tried include DynArray, include Extlib, nothing works
2021-06-05 23:23:07	companion_cube>	you need to have it in your dune file, if you use dune
2021-06-05 23:23:10	companion_cube>	and to install it in the first place
2021-06-05 23:24:09	kluk>	I don't know what dune is yet, I'm still a beginner at OCaml. how do I install DynArray? with opam right?
2021-06-05 23:24:51	companion_cube>	hmmm if you're  that beginner, maybe take a look at a book 
2021-06-05 23:24:55	companion_cube>	there's a lot to explain :/
2021-06-05 23:26:43	kluk>	I just wanted to play around on the ocaml repl with some arrays... not looking for making a project, folders, dune stuff, any of that, if possible to avoid at this point. Is it possible to just play with the OCaml language to learn it and not worry about how it mixes up with unix?
2021-06-05 23:27:56	companion_cube>	ah well, sure, just type `ocaml`
2021-06-05 23:28:07	companion_cube>	but Dynarray is a 3rd party library for vectors/resizable arrays
2021-06-05 23:28:16	companion_cube>	it's not exactly a central type in OCaml :
2021-06-05 23:28:17	companion_cube>	:p
2021-06-05 23:29:14	kluk>	yes I can get to the repl, but I wanted to play with arrays first without worrying about packages, does that make sense? I wanted to explore OCaml the language first, like a try.ocaml.org sort of thing if that makes sense... I wanted to have some fun with the language and learn it and not have to think about packages and managing projects for a little
2021-06-05 23:30:40	kluk>	I need a stack whose elements can be randomly accessed by an integer so I just happen to have an exact use case for arrays, but I am open to suggestions
2021-06-05 23:34:07	companion_cube>	arrays are in the stdlib
2021-06-05 23:34:17	companion_cube>	not dynamic arrays
2021-06-05 23:34:31	companion_cube>	but yeah, a stack with indexing is a good use case
2021-06-05 23:34:55	kluk>	companion_cube :)
2021-06-06 00:03:27	d_bot>	<Bluddy> IMO vectors should replace arrays as a primary data type in the language
2021-06-06 00:04:29	companion_cube>	why "replace"?
2021-06-06 00:04:42	companion_cube>	I think it'd be nice to be able to build them safely
2021-06-06 00:04:47	d_bot>	<Bluddy> as the *primary* data type
2021-06-06 00:04:51	companion_cube>	but otherwise, they have some overhead
2021-06-06 00:05:03	companion_cube>	arrays are simpler as they're always fully initialized
2021-06-06 00:05:11	d_bot>	<Bluddy> yeah the overhead is very minor though
2021-06-06 00:05:34	d_bot>	<Bluddy> very few languages have arrays as their primary data structure
2021-06-06 00:05:48	d_bot>	<Bluddy> python's lists are vectors
2021-06-06 00:05:49	companion_cube>	I mean… java?
2021-06-06 00:06:12	companion_cube>	I think the problem is the GC, because in a vector you need some unitialized space
2021-06-06 00:06:15	companion_cube>	even in rust it's quite dirty
2021-06-06 00:06:46	d_bot>	<Bluddy> hmm
2021-06-06 00:07:10	companion_cube>	it's hard to do well without a bit of Obj currently :/
2021-06-06 00:08:53	d_bot>	<Bluddy> ok so I guess python/ruby's bias may be due to their reference counting
2021-06-06 00:09:11	companion_cube>	also they're insanely high level and slow :p
2021-06-06 00:09:39	d_bot>	<Bluddy> yeah but that's beside the point. java has array, c# has array vs List (really a vector)
2021-06-06 00:09:54	companion_cube>	java has ArrayList, but only for boxed types
2021-06-06 00:09:59	companion_cube>	the primitive on the JVM is arrays, same as OCaml
2021-06-06 00:10:07	companion_cube>	(except with unsound variance)
2021-06-06 00:10:12	d_bot>	<Bluddy> right
2021-06-06 00:10:30	d_bot>	<Bluddy> ok so yeah I think I'm just using python too much recently
2021-06-06 00:11:00	d_bot>	<Bluddy> javascript also has array as its primary type
2021-06-06 00:11:07	companion_cube>	remember that in OCaml, an array is *one* word of overhead
2021-06-06 00:11:12	d_bot>	<Bluddy> so are python and ruby really the exceptions?
2021-06-06 00:11:26	companion_cube>	as far as primitive types go? I'm not sure
2021-06-06 00:13:25	d_bot>	<EduardoRFS> JS arrays are dynamic arrays / vectors
2021-06-06 00:13:34	d_bot>	<EduardoRFS> and the implementation of it is really all over the place
2021-06-06 00:13:51	d_bot>	<Bluddy> perl has dynamic arrays. also reference counted
2021-06-06 00:14:18	companion_cube>	_scripting languages_ were primitives are all in C
2021-06-06 00:15:51	d_bot>	<Bluddy> interesting. and it's gc'd.
2021-06-06 00:16:30	d_bot>	<Bluddy> @companion_cube GC is only an issue if you don't have a bit to tell the GC not to scan the uninitialized memory. If OCaml had it, it wouldn't be an issue.
2021-06-06 00:16:58	companion_cube>	sure, if you entirely rewrite the GC so it's not just based on the initial tag… :p
2021-06-06 00:17:13	d_bot>	<EduardoRFS> but JS objects nowadays operates like OCaml blocks, adding and removing field is generally a bad idea because of the types, while it is possible that can trigger a whole lot of compiled and optimized code to be invalidated
2021-06-06 00:17:15	d_bot>	<Bluddy> hmm.. no I guess you need to build it into the GC process itself so it knows how to process the vector
2021-06-06 00:17:24	d_bot>	<Bluddy> so it looks at length vs capacity
2021-06-06 00:17:26	d_bot>	<EduardoRFS> well we can extend the object header
2021-06-06 00:17:26	companion_cube>	(well for a vector you'd need to fit 2 sizes in one, basically: capacity, and actual size)
2021-06-06 00:17:35	d_bot>	<EduardoRFS> I'm looking on it during the shower
2021-06-06 00:17:52	d_bot>	<Bluddy> yeah a bit is not enough, you need to teach the GC about a new kind of object
2021-06-06 00:18:00	companion_cube>	also remember that vectors are 2 levels of indirection, not one
2021-06-06 00:18:06	companion_cube>	one to the {len,capacity,ptr}
2021-06-06 00:18:12	companion_cube>	+ the pointer itself
2021-06-06 00:18:31	companion_cube>	but you've got to have this level of indirection so you can change the underlying array/pointer
2021-06-06 00:19:02	d_bot>	<Bluddy> that's true
2021-06-06 00:19:36	companion_cube>	so that's non trivial overhead compared to a basic array, when all you need is an array
2021-06-06 00:19:53	d_bot>	<EduardoRFS> but that access can be mostly reduced if you know the cell size at compile time
2021-06-06 00:19:56	d_bot>	<Bluddy> the problem is that you very rarely need an array
2021-06-06 00:20:38	d_bot>	<Bluddy> if your primary type is a list, all an array gives you is mutability + O(1) access to any element. it's good, but the lack of ability to extend it is annoying
2021-06-06 00:20:46	d_bot>	<Bluddy> if you're doing mutable stuff, you almost always want to extend it
2021-06-06 00:20:56	companion_cube>	idk, it's nice in ASTs for example
2021-06-06 00:21:03	companion_cube>	I agree that often a vector is also useful
2021-06-06 00:22:19	d_bot>	<EduardoRFS> I wonder if having an unrolled linked list with some tricks wouldn't be enough for almost all cases
2021-06-06 00:22:53	companion_cube>	for mutable stuff we just should have a good vector
2021-06-06 00:22:59	d_bot>	<EduardoRFS> like couple cells all cache aligned + pointers to additional cells if they were created all together so that you can do O(1) after a List.map
2021-06-06 00:23:03	companion_cube>	for immutable stuff, we _could_ use HAMT… but well
2021-06-06 00:25:01	d_bot>	<EduardoRFS> copy on write is the solution to all problems
2021-06-06 00:25:11	companion_cube>	noooo :D
2021-06-06 00:27:33	d_bot>	<EduardoRFS> computers are fun, nowadays you have an ALU and caching inside of the MMU
2021-06-06 00:28:05	d_bot>	<EduardoRFS> lisp machine to rule them all
2021-06-06 00:51:48	d_bot>	<Bluddy> companion_cube: what do you do to prevent the GC from scanning the uninitialized vector area?
2021-06-06 00:53:27	d_bot>	<EduardoRFS> If it is set to 0x0 the GC should just behave normally, it's a block of tag 0, size 0
2021-06-06 00:57:50	companion_cube>	@Bluddy in containers, indeed, I fill the vector with 0
2021-06-06 00:58:03	companion_cube>	or 0.0 if it's a float array 🙄
2021-06-06 01:34:37	d_bot>	<Bluddy> ugh yeah that's bad
2021-06-06 01:34:57	companion_cube>	not like we have a better option, imhp
2021-06-06 01:34:59	companion_cube>	imho
2021-06-06 01:37:39	d_bot>	<Bluddy> I wonder what other languages do
2021-06-06 01:37:44	d_bot>	<Bluddy> ones with GC
2021-06-06 01:40:49	companion_cube>	well, java fills with null I imagine
2021-06-06 01:40:54	companion_cube>	boxed primitives and all that
2021-06-06 01:41:03	companion_cube>	D… probably does ugly stuff?
2021-06-06 01:41:10	companion_cube>	Go has 0 values for all types, so that's easy
2021-06-06 01:41:31	companion_cube>	and the scripting stuff has nil/None/whatever to fill the blanks
2021-06-06 01:42:17	d_bot>	<Bluddy> at the Obj level it would be nice if you could have a contiguous array where the size is the length, and right after that you'd place a string header with the remaining size
2021-06-06 01:42:38	companion_cube>	you'd have to move the header every time you push/pop? :/
2021-06-06 01:42:48	d_bot>	<Bluddy> not a huge deal. same cache line
2021-06-06 01:43:07	companion_cube>	ideally push should be as simple and inlineable as possible :p
2021-06-06 01:43:53	d_bot>	<Bluddy> still pretty simple. copy header over, reduce string size
2021-06-06 01:44:34	companion_cube>	+ code path for possible resize… that's a lot more than just a normal push
2021-06-06 01:44:37	d_bot>	<Bluddy> pop doesn't need to do anything because you can just zero data out at that point
2021-06-06 01:45:12	d_bot>	<Bluddy> that code path is there regardless
2021-06-06 01:45:38	d_bot>	<Bluddy> a multi-push function can be more efficient as it can do the header copy once
2021-06-06 01:45:59	companion_cube>	pop still needs to copy the header back
2021-06-06 01:46:58	d_bot>	<Bluddy> yeah I guess that's true. the only annoying thing about the header is the size counter
2021-06-06 01:47:20	companion_cube>	I'd rather wish OCaml had a primitive for partially initialized arrays, and that's it
2021-06-06 01:47:22	d_bot>	<Bluddy> but it should be doable with a couple of instructions
2021-06-06 01:47:43	d_bot>	<Bluddy> well that's not going to happen anytime soon
2021-06-06 01:48:23	d_bot>	<Bluddy> it can happen in the 64-bit runtime, but the 32-bit cannot handle it
2021-06-06 01:48:38	d_bot>	<Bluddy> because you need that extra header space for the size
2021-06-06 01:48:39	companion_cube>	not sure how that's related :p
2021-06-06 01:49:03	companion_cube>	I just want an API for the array with a valid 0 inside
2021-06-06 01:49:16	companion_cube>	that doesn't force me to Obj.magic to see if it's a float array or normal array
2021-06-06 01:49:16	d_bot>	<Bluddy> valid 0?
2021-06-06 01:49:26	companion_cube>	a valid object for this array
2021-06-06 01:49:42	companion_cube>	a valid object for this array, _as seen by the GC_
2021-06-06 01:51:38	d_bot>	<Bluddy> is this another wish? to deal more easily with float arrays? or is it related?
2021-06-06 01:51:58	companion_cube>	it's related because it's the only reason I have to use Obj in containers :p
2021-06-06 01:52:04	companion_cube>	(or one of the few, I can't remember)
2021-06-06 01:52:20	companion_cube>	to be able to implement a vector
2021-06-06 01:52:39	d_bot>	<Bluddy> but it doesn't deal with this particular issue
2021-06-06 01:52:47	d_bot>	<Bluddy> I mean they're phasing out float arrays
2021-06-06 01:52:57	companion_cube>	yeah that'll be nice
2021-06-06 01:53:16	companion_cube>	without float arrays one could always fill the array with 0
2021-06-06 01:53:29	companion_cube>	since the GC doesn't mind 0
2021-06-06 01:53:55	d_bot>	<Bluddy> yeah I see that piece of code now
2021-06-06 01:54:12	d_bot>	<Bluddy> let fill_with_junk_ (a:_ array) i len : unit =
2021-06-06 01:54:15	companion_cube>	yep yep
2021-06-06 01:54:27	d_bot>	<Bluddy> https://github.com/c-cube/ocaml-containers/blob/95e96fb5e12558fa5b1e907a8e315d8c859c23b8/src/core/CCVector.ml#L27
2021-06-06 01:54:29	companion_cube>	always interested in better ideas
2021-06-06 02:04:20	d_bot>	<ggole> For 64-bit machine zero (not OCaml zero) is fine for float arrays as well
2021-06-06 02:05:07	d_bot>	<ggole> So you might be able to get away with coercing to `float array` and then filling with `0.0`
2021-06-06 02:05:26	d_bot>	<ggole> However, the recent `FloatArray` stuff might kill that idea
2021-06-06 02:08:30	d_bot>	<ggole> The no naked pointer changes might also be trouble
2021-06-06 03:32:21	d_bot>	<aotmr> Hi everyone! I'm a 3rd-year CS student making personal explorations into programming languages with an emphasis on functional and concatenative languages, as well as metaprogramming and optimizing compilers.
2021-06-06 03:33:32	d_bot>	<aotmr> I'm currently using OCaml to build a functional FORTH interpreter that I hope to shape into a general optimizing FORTH compiler
2021-06-06 03:33:49	d_bot>	<aotmr> And right now I'm investigating to what extent I can express FORTH concepts in OCaml
2021-06-06 03:42:01	d_bot>	<ggole> Hmm, they're pretty different
2021-06-06 03:43:21	d_bot>	<ggole> OCaml code is very variable heavy, which seems to be at odds with the Forth philosophy of communicating between tiny bits with the stack
2021-06-06 03:43:38	d_bot>	<aotmr> So, for example, inside my VM state is a list representing the current data stack.
2021-06-06 03:43:38	d_bot>	<aotmr> ```ocaml
2021-06-06 03:43:40	d_bot>	<aotmr> type state = {
2021-06-06 03:43:41	d_bot>	<aotmr>     ds : Int.t list;
2021-06-06 03:43:42	d_bot>	<aotmr>     (* ... *)
2021-06-06 03:43:44	d_bot>	<aotmr> }
2021-06-06 03:43:45	d_bot>	<aotmr> ```
2021-06-06 03:43:46	d_bot>	<aotmr> Stack-based interpreters are excellent matches for programming languages with pattern matching facilities, as it turns out.
2021-06-06 03:44:15	d_bot>	<aotmr> ```ocaml
2021-06-06 03:44:16	d_bot>	<aotmr> type opcode =
2021-06-06 03:44:17	d_bot>	<aotmr>     | Lit of Int.t
2021-06-06 03:44:19	d_bot>	<aotmr>     | Add
2021-06-06 03:44:20	d_bot>	<aotmr>     | Dot
2021-06-06 03:44:21	d_bot>	<aotmr>     (* ... *)
2021-06-06 03:44:23	d_bot>	<aotmr> ```
2021-06-06 03:44:41	d_bot>	<aotmr> Let's define a small opcode set for our VM: push a literal to the stack, add the top two on the stack, and print the top on the stack (`Dot`)
2021-06-06 03:46:01	d_bot>	<aotmr> Now, here's where OCaml's list matching becomes very elegant. Let's define a function, `execute`, that takes a state and an opcode and returns a new state that reflects having executed the opcode.
2021-06-06 03:46:01	d_bot>	<aotmr> ```ocaml
2021-06-06 03:46:03	d_bot>	<aotmr> let execute st = function
2021-06-06 03:46:04	d_bot>	<aotmr> | Lit i -> { st with ds = i::st.ds }
2021-06-06 03:46:05	d_bot>	<aotmr> | Add -> (* ... *)
2021-06-06 03:46:07	d_bot>	<aotmr> | Dot -> (* ... *)
2021-06-06 03:46:08	d_bot>	<aotmr> ```
2021-06-06 03:46:32	d_bot>	<colin> awaiting the IRC users who'll ask you to read the channel description
2021-06-06 03:46:43	d_bot>	<aotmr> Aw shit 🤦‍♂️
2021-06-06 03:46:49	d_bot>	<colin> :p
2021-06-06 03:46:52	zozozo>	@aotmr : code blocks from discord do not render great on the irc side of this channel, so it'd be best if you could use some paste website to link to code when there are more than a few lines, ^^
2021-06-06 03:46:59	d_bot>	<aotmr> There it is
2021-06-06 03:47:08	zozozo>	haha, XD
2021-06-06 03:47:32	d_bot>	<aotmr> Well all that goes to say
2021-06-06 03:47:32	d_bot>	<aotmr> You can express stack operations using pattern matching.
2021-06-06 03:48:43	d_bot>	<colin> if you think that's cute, you'll like a similar idea in dependent typing where you can express stack changes (as a list) indexing the opcodes or something similar
2021-06-06 03:48:44	d_bot>	<aotmr> For example, to swap the top two items on the stack, you'd use the record update syntax
2021-06-06 03:48:45	d_bot>	<aotmr> `{ st with ds = match st.ds with a:🅱️:tl -> b:🅰️:tl | _ -> assert false }`
2021-06-06 03:48:46	d_bot>	<aotmr> Last code block for the time being, I promise 😅
2021-06-06 03:49:17	d_bot>	<aotmr> (And you can also use `let` matching, I've found, but I can't get ocaml to stop complaining even though I fully understand it'll crash if there aren't enough elements)
2021-06-06 03:49:30	d_bot>	<aotmr> Oh, have a paper on that?
2021-06-06 03:49:54	d_bot>	<aotmr> I'm wanting to see how high-level I can get with forth and still generate good code for small microprocessors--say, for NES and game boy dev
2021-06-06 03:50:06	d_bot>	<colin> no, just thought it was very cute when I studied Agda at university, relevant construction of Hutton's razor can be found at https://github.com/fredrikNordvallForsberg/CS410-20/blob/master/Coursework/Two.agda#L492-L506 what you're saying just reminded me of it, not really relevant just in case you wanted to see cute things
2021-06-06 03:50:15	zozozo>	@aotmr : small one-line blocks of code (like your last one) are mostly okay I'd say, ^^
2021-06-06 03:50:48	d_bot>	<aotmr> Oh I'll look at it never the less, thanks.
2021-06-06 03:50:49	d_bot>	<aotmr> Forth has its own concept of combinators and I want to try to compile those efficiently
2021-06-06 03:52:04	d_bot>	<aotmr> Honestly I'd say OCaml is distantly related to FORTH just usagewise, there's a similar concept of "pipelining". Where in FORTH you'd write a series of words, passing state between them implicitly on the stack, you do the same in Ocaml when expressing a `|>` or `@@` pipeline
2021-06-06 03:54:16	d_bot>	<aotmr> This is an interesting idea as, while FORTH is typically untyped, I could use this concept to track the entire lifetimes of values throughout a program
2021-06-06 03:55:20	d_bot>	<colin> it's just a nice encoding of how the stack ought to change, helps the type system help you implement it correctly (though not a full specification by any means, just a cute stack requirement)
2021-06-06 03:55:27	d_bot>	<ggole> There are some interesting typed concatenative langs
2021-06-06 03:55:47	d_bot>	<ggole> Kitten and Cat
2021-06-06 03:55:48	d_bot>	<aotmr> I've finally taken the forth-pill so to speak because I finally understand how to implement a compiler for the language
2021-06-06 03:56:18	d_bot>	<colin> a whole new world.mp3 https://llvm.moe/
2021-06-06 03:56:29	d_bot>	<colin> see past stack-based paradigm
2021-06-06 03:56:58	d_bot>	<aotmr> Well, once I have a compiler for a stack-based VM that opens the door to using it as an intermediate representation
2021-06-06 03:57:14	d_bot>	<colin> would there be any benefit
2021-06-06 03:57:27	d_bot>	<colin> I, admittedly, have never seen the appeal of stack-based languages for general programming
2021-06-06 03:57:32	d_bot>	<colin> I used to write postscript by hand recreationally
2021-06-06 03:57:35	d_bot>	<colin> but that's about it
2021-06-06 03:57:46	d_bot>	<aotmr> It's admittedly kind of recreational
2021-06-06 03:58:10	d_bot>	<aotmr> I think the real strength is in the way you can build an entire system from the ground up by hand and know every moving part
2021-06-06 03:59:32	d_bot>	<aotmr> You could write an optimizing compiler x86 in, oh, a month
2021-06-06 04:00:51	d_bot>	<colin> sadly the majority of back-end optimisations for x86 are really just suffering
2021-06-06 04:00:59	d_bot>	<aotmr> OCaml's own VM is stack-based so it's kind of circular
2021-06-06 04:01:09	d_bot>	<colin> yeah but that's just the bytecode OCaml stuff
2021-06-06 04:01:12	d_bot>	<aotmr> Oh yeah no x86 is a horrible architecture to program for
2021-06-06 04:01:19	d_bot>	<aotmr> Sure but it's still a neat thought
2021-06-06 04:01:25	d_bot>	<aotmr> But I digress
2021-06-06 04:01:28	d_bot>	<colin> I used to be confused as to why Xavier Leroy's earlier work seemed to focus rather specifically on bytecode stack machines as the target of Camls
2021-06-06 04:01:51	d_bot>	<colin> but then someone said like "it was research into creating a tactic computational kernel for some proof assistant"
2021-06-06 04:02:01	d_bot>	<colin> not sure how true that is, perhaps someone here can clarify if that's nonsense
2021-06-06 04:02:07	d_bot>	<colin> and Xavier just really likes stack machines
2021-06-06 04:02:56	d_bot>	<aotmr> So, it could be that you can take advantage of immutable VM states in unit testing
2021-06-06 04:03:13	d_bot>	<aotmr> And using it to accelerate the general process
2021-06-06 04:04:16	d_bot>	<aotmr> If you wanted to do an exhaustive search of the program P with inputs a, b, c..., you could run P over every possible value of a, b, c
2021-06-06 04:05:19	d_bot>	<aotmr> That is, we're trying to find a, b, c... that causes P to fail
2021-06-06 04:06:00	d_bot>	<ggole> There's actually some tooling for that
2021-06-06 04:06:02	d_bot>	<ggole> See Crowbar
2021-06-06 04:06:08	d_bot>	<aotmr> One way to speed up that process is to memoize the VM state, I think
2021-06-06 04:06:44	d_bot>	<ggole> It's not exhaustive search, but coverage-feedback guided random generation
2021-06-06 04:06:47	d_bot>	<aotmr> If we find a "success" set of (a, b, c...), we could maybe remember all of the previous states of the VM and if we ever encounter them again we can stop early
2021-06-06 04:07:14	d_bot>	<aotmr> But that would blow up your space requirements for little speedup, I'd think
2021-06-06 04:07:17	d_bot>	<colin> can see why that'd help (as a form of concolic execution) but I think the accepted reality in industry is that Google fuzz their own software over billions of instances using AFL on dozens of Google cloud instances and just consider that alright
2021-06-06 04:08:00	d_bot>	<aotmr> My other use case is of a rewindable debugger where you can undo all the way back to the start of the program
2021-06-06 04:08:51	d_bot>	<colin> time travel debugging is pretty cool
2021-06-06 04:09:07	d_bot>	<aotmr> That also brings to mind the idea of a rewindable game engine, I think rewind mechanics are pretty cool in theory
2021-06-06 04:09:12	d_bot>	<colin> I always wanted a clean injection mechanism for debugging
2021-06-06 04:09:27	d_bot>	<colin> hot reloading debugging stubs, that kinda thing
2021-06-06 04:09:54	d_bot>	<aotmr> I'm still not entirely familiar with the mechanics of debuggers
2021-06-06 04:10:07	d_bot>	<colin> syscalls and suffering™️
2021-06-06 04:10:36	d_bot>	<aotmr> I'm under the impression that, if you can execute from RAM, you can at least single-step on pretty much any CPU
2021-06-06 04:11:58	d_bot>	<colin> yeah there's architectural single step stuff provided by most systems; *nix has PTRACE_SINGLESTEP
2021-06-06 04:12:02	d_bot>	<aotmr> If you want to single-step the instruction at a given address, then you'd write some kind of "breakpoint" opcode (or, crudely, even just an absolute jump) directly following it, but you'd have to know the length of the opcode beforehand
2021-06-06 04:12:27	d_bot>	<aotmr> But I'd hope consumer CPUs can single-step in silicon by now 😅
2021-06-06 04:12:28	d_bot>	<colin> variable length encoding is just one part of suffering in writing x86(_64) tooling, yes
2021-06-06 04:12:42	d_bot>	<aotmr> Oh yeah I guess debugging has to be infinitely easier on a fixed-length RISC
2021-06-06 04:13:14	d_bot>	<aotmr> Imagine if x86 had an instruction that only decoded the length of an instruction at a given address
2021-06-06 04:13:18	d_bot>	<colin> I suppose there's other challenges, given the domain where RISC microprocessors are probably most prevalently being debugged
2021-06-06 04:13:39	d_bot>	<colin> who knows, they might, Intel has a ton of hidden instructions and their manual doesn't even document some of them accurately
2021-06-06 04:13:46	d_bot>	<aotmr> You're right, there probably is.
2021-06-06 04:14:06	d_bot>	<ggole> There's tons of hardware support for debugging
2021-06-06 04:14:09	d_bot>	<colin> it's common for trampoline hooking code to come with a "variable length decoder" as a form of minimal disassembler
2021-06-06 04:14:13	d_bot>	<ggole> Watch registers and that kind of thing
2021-06-06 04:14:26	d_bot>	<ggole> Pretty complicated from what I understand
2021-06-06 04:14:27	d_bot>	<colin> to know how many bytes to replace w/ their placed `jmp` or `push ...; ret` etc.
2021-06-06 04:16:26	d_bot>	<colin> but yeah, can't lie
2021-06-06 04:16:34	d_bot>	<colin> confused how we went from stack langs to all this
2021-06-06 04:16:58	d_bot>	<colin> what is your ambition, aotmr, to write a forth interpreter/compiler?
2021-06-06 04:19:34	d_bot>	<aotmr> Just to do it, I guess. I think it's interesting to build a software stack nearly from the bottom up--or nearly so
2021-06-06 04:19:53	d_bot>	<colin> what, in Forth?
2021-06-06 04:20:04	d_bot>	<aotmr> I mean, build a Forth itself from the bottom up
2021-06-06 04:20:14	d_bot>	<colin> oh alright
2021-06-06 04:20:29	d_bot>	<aotmr> In theory it can even be possible to replace the Ocaml parts with Forth themselves
2021-06-06 04:21:15	d_bot>	<aotmr> Though "bootstrapping"
2021-06-06 04:21:47	d_bot>	<aotmr> First, I'd write a forth compiler in ocaml
2021-06-06 04:22:07	d_bot>	<aotmr> Then, translate the compiler to forth
2021-06-06 04:22:17	d_bot>	<aotmr> Compile the compiler-in-forth with the compiler-in-ocaml
2021-06-06 04:22:30	d_bot>	<aotmr> And then I have a forth compiler, compiled and written in forth
2021-06-06 04:22:36	d_bot>	<colin> can graduate to something hacky like JITing the FORTH then using C FFI to map the code and somehow return opaque caml values back to the user as callables within OCaml
2021-06-06 04:22:55	d_bot>	<colin> galaxy brain interplay
2021-06-06 04:23:14	d_bot>	<aotmr> That sounds terrifying
2021-06-06 04:23:22	d_bot>	<colin> -ly based
2021-06-06 04:23:28	d_bot>	<aotmr> You got it
2021-06-06 04:23:44	d_bot>	<colin> don't actually know if you can do that
2021-06-06 04:23:52	d_bot>	<colin> on the conceptual level, you certainly can with enough hacks
2021-06-06 04:24:21	d_bot>	<aotmr> Probably the easiest way to "JIT" stack code is just to apply peephole optimization
2021-06-06 04:24:34	d_bot>	<colin> can't lie, I hate stacks
2021-06-06 04:24:56	d_bot>	<aotmr> The compiler writer writes manual superwords that implement a series of smaller words in a faster way
2021-06-06 04:26:26	d_bot>	<aotmr> For example, replacing `>r + r>` with the much shorter machine code for the equivalent sequence that just adds the top element of the stack to the third
2021-06-06 04:42:07	d_bot>	<BobbyT> I’m just marinating in all these high level ideas
2021-06-06 05:58:42	ralu>	I am trying to build infer, but I keep getting error about failed dune build. So i can not build dune. Has anyone has any pointers?
2021-06-06 09:38:22	d_bot>	<Bluddy> What if we make it so a proper null pointer inside an array means the end of GC scanning?
2021-06-06 10:32:24	d_bot>	<Drup> @Bluddy that's not compatible with a bunch of much more interesting representations improvements (like democratizing the Zarith hack, for instance)
2021-06-06 10:52:39	d_bot>	<Deadrat> Would lightweight higher kinded types be added to ocaml in the future?
2021-06-06 10:58:32	d_bot>	<xvw> With modular immlicits I guess that lightweight higher kinded types will be less useful
2021-06-06 11:08:02	d_bot>	<rbrott> There's a nice chapter on that idea in CPDT: <http://adam.chlipala.net/cpdt/html/Cpdt.StackMachine.html>
2021-06-06 11:08:04	d_bot>	<Bluddy> @Drup could you explain the 'zarith hack'?
2021-06-06 11:09:03	d_bot>	<Deadrat> But they are still years away as I understand?
2021-06-06 11:09:35	d_bot>	<Drup> @Bluddy A value of type `Z.t` in zarith is either a normal ocaml integer (63bits usually, etc) or a GMP "big integers"
2021-06-06 11:11:56	d_bot>	<Drup> This is achieved by considering the type morally as `int | Big of gmp`. OCaml integers already have a bit put aside for the GC to differentiate them from pointers, so we don't need an extra tag to differentiate between small integers and pointers to a big integer.
2021-06-06 11:12:15	d_bot>	<Drup> This is only possible by going through the C FFI
2021-06-06 11:12:29	d_bot>	<ggole> Machine zero isn't an `int` or a block though
2021-06-06 11:15:09	d_bot>	<Drup> @ggole I can never remember if the tag for integers is 0 or 1.
2021-06-06 11:17:58	d_bot>	<ggole> It's 1
2021-06-06 11:18:24	d_bot>	<ggole> But even if it were zero, you could set aside a non-valid pointer value to indicate a truncation spot
2021-06-06 11:20:59	d_bot>	<Drup> right, I'm not sure how much I like it, but it could work
2021-06-06 11:26:30	d_bot>	<ggole> I guess there would have to be an `Array.unsafe_set_terminator` or something, which would be a bit nasty
2021-06-06 11:26:41	d_bot>	<ggole> And I dunno what the interaction with bounds checking would be
2021-06-06 11:27:07	d_bot>	<ggole> I suspect they would be more trouble than the terminator value itself though
2021-06-06 11:49:23	d_bot>	<Bluddy> I need to try it out and see the performance difference.
2021-06-06 11:51:38	d_bot>	<Bluddy> it's not automatically clear that setting all the memory is a bad idea
2021-06-06 13:00:48	companion_cube>	I'd just like to point out that no one else uses a terminator for vectors, afaik
2021-06-06 13:00:55	companion_cube>	it seems like a pretty bad idea :p
2021-06-06 13:05:10	d_bot>	<ggole> Most of the other langs with vectors can handle uninitialised memory or keep the bits there without leaks
2021-06-06 13:06:34	companion_cube>	and again, it's not that common
2021-06-06 13:06:57	companion_cube>	languages that compile to native and have a GC and don't rely on C to implement a ton of datastructures are not plenty
2021-06-06 13:47:15	d_bot>	<aotmr> I'm still not entirely used to building data structures in any language *but* C, to be honest--it feels strange
2021-06-06 13:47:52	d_bot>	<aotmr> I probably just don't have practice because C is the only language that I use that doesn't have a dynamic array, really
2021-06-06 13:48:49	companion_cube>	well OCaml is excellent for implementing a lot of data structures
2021-06-06 13:49:01	companion_cube>	vectors just happen to be a bit on the low-level, unsafe memory thingie side
2021-06-06 13:51:37	d_bot>	<aotmr> What's a good way to map from a discriminated union to successive integers?
2021-06-06 13:51:43	d_bot>	<aotmr> And the other way around?
2021-06-06 13:53:53	companion_cube>	ppx_deriving.enum maybe?
2021-06-06 13:54:02	companion_cube>	if it's an enum, without payload on the variants, that is.
2021-06-06 13:57:14	d_bot>	<aotmr> Hmm
2021-06-06 13:57:14	d_bot>	<aotmr> Here's a simpler question: how do I get the "tag" of a sum type?
2021-06-06 13:57:41	companion_cube>	you don't :)
2021-06-06 13:57:45	d_bot>	<aotmr> I figure I can quickly map integers to most of the opcodes and then manually handle opcodes with a payload
2021-06-06 13:57:47	companion_cube>	it's not really specified in the language.
2021-06-06 13:57:48	d_bot>	<aotmr> Oh...
2021-06-06 13:57:52	d_bot>	<octachron> The simpler and most forward-compatible way is to write the function.
2021-06-06 13:58:11	d_bot>	<aotmr> True, but then I'd have to write two functions and keep them in sync manually, or generate the code.
2021-06-06 13:58:35	d_bot>	<aotmr> *sigh* Okay then
2021-06-06 13:58:37	companion_cube>	the function from integers to variants seems impossible to write
2021-06-06 13:58:45	companion_cube>	if they have payloads that is
2021-06-06 13:58:56	d_bot>	<aotmr> I'd be converting from a packed representation
2021-06-06 14:01:41	companion_cube>	your best chance is codegen indeed
2021-06-06 14:01:53	companion_cube>	variant to int: generate a pattern matching function
2021-06-06 14:02:10	companion_cube>	int+payload to variant: well, match on the int I guess
2021-06-06 14:04:58	d_bot>	<aotmr> Actually wait, I'm wrong
2021-06-06 14:04:58	d_bot>	<aotmr> I shouldn't have written the VM with a discriminated union like this anyways
2021-06-06 14:05:13	d_bot>	<aotmr> But, I guess I might as well keep a separate encoded and decoded form
2021-06-06 14:10:07	companion_cube>	a VM seems like a good use case for C or C++ or rust, ironically
2021-06-06 14:23:33	d_bot>	<aotmr> Oh it's definitely more appropriate, but I'm actually making some headway
2021-06-06 14:24:11	d_bot>	<aotmr> I haven't played with ocaml in quite some time (OS issues--it didn't work well on Windows for me until quite recently)
2021-06-06 14:24:23	companion_cube>	glad to hear it works better now
2021-06-06 14:24:45	d_bot>	<aotmr> I mean, it works better now because it's running in WSL 😆
2021-06-06 14:25:44	d_bot>	<aotmr> So I'm happy that I remember how to build list to list mappings that produce and consume varying numbers of elements
2021-06-06 15:08:24	d_bot>	<aotmr> Cool, so I've figured out how to build an encoder and decoder for a variable-length instruction stream
2021-06-06 18:00:25	kluk>	I get "Error: Unbound module Batteries" after doing open Batteries;; on the ocaml repl after having done opam install batteries. what am I missing?
2021-06-06 18:04:03	companion_cube>	#require "batteries";;
2021-06-06 18:04:12	companion_cube>	(and possibly, before that, #use "topfind";;)
2021-06-06 18:07:13	kluk>	Ahhh.. it wasn't clear to me that #use was needed to bring #require but now that I ran it I can see in its blurb that it does do that. Thank you very much.
2021-06-06 18:07:49	companion_cube>	also note that if you use `utop` it does the topfind thing directly
2021-06-06 18:08:03	companion_cube>	you can also put the blurb in ~/.ocamlinit
2021-06-06 18:11:31	kluk>	companion_cube thank you for the .ocamlinit tip
2021-06-06 18:27:10	kluk>	companion_cube so now I can use DynArray from Batteries just fine :) thanks so much for the help once again.
2021-06-06 18:35:30	companion_cube>	heh