<rosalogia>
Hey everyone, super beginner question I apologise, but I'm wondering about the double semicolon and when it becomes necessary in .ml files? I'm generally struggling to find extensive documentation on how to work with .ml files and what the conventions are
<rosalogia>
I've seen a lot of "the double-semicolon isnt actually part of the language and is completely unnecessary outside of utop" but I'm having trouble getting my programs to compile if I don't use a double-semicolon at least once before invoking the main function (which, again, please let me know if I'm wrong to be using one)
<def>
rosalogia: you can use a let-binding in place of semicolon
<def>
<expr>;; is useful in the top-level
<def>
but `let my_name = <expr>` is preferred in an ml file
<def>
`let () = main ()` for side-effectful functions
<def>
or `let _ = <expr>` to just ignore the result of an expression though is generally not recommended
<rosalogia>
ohh
<rosalogia>
let me try that
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<rosalogia>
that works perfectly :) thanks for clarifying, appreciate it a lot
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<olle>
how come ownership inference never made it to a language? I wonder why Rust went with explicit ownership :d
<olle>
maybe it's easier to reason about?
<olle>
or easier to read the code
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<Leonidas>
rosalogia: it shouldn't ever be required. if it does then there might be something subtly wrong with your code, with it doing a different thing than you might expect it to do.
<rosalogia>
thank you! :)
<Leonidas>
olle: explicit ownership is tracking the somewhat implicit concept of ownership from languages like C into a formal system that the compiler can enforce
<olle>
Leonidas: sure, but you can also infer it with escape analysis, e.g.
<olle>
meaning, ownership is transfered iff the variable cannot escape
<olle>
there are some papers on it online
<olle>
rust went another way, tho
<flux1>
it seems like actually deploying it to a useful language with mutation, lambda functions, threading, objects can be quite a task while at the same time having small syntax. I wonder if this really was a solved problem at the time when OCaml was devised?
<flux1>
and I do wonder if tracing garbage collector is at all compatible. ie. Rust doesn't do it.
<olle>
sure
<olle>
Clean has uniqueness types, slightly related
<flux1>
too bad Clean is proprietary, its ideas might have more impact otherwise
<olle>
it is? didn't know
<flux1>
hmm, it seems Clean 3.0 is available under "Simplified BSD license"
<flux1>
and even before it appears to have been under LGPL or proprietary, so I guess it's been fine
<Drup>
Clean is open source, and there are several papers on its type system
<olle>
oooh
<olle>
ok
<Drup>
flux1: a GC is mostly compatible. Rust doesn't have GC because the memory representation is highly non-uniform. It has RC, but it requires explicit boxing and various use of traits, it's very clunky to use
<olle>
but it doesn't need it, right?
<olle>
because of the ownership control
<Drup>
You don't want maximal control all the time
<Drup>
sometimes, you just want the damn thing not to make segfaults
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<olle>
I've heard that's highly immoral ;)
<Drup>
said the php programmer
<olle>
haha
<olle>
it's a joke they run at /r/programmingcirclejerk
<olle>
that rust is the moral choice
<olle>
btw, if i get my next patch accepted to psalm (php static analyzer), i might start to work on some escape analysis for it. they already have flow analysis for null values.
<olle>
then it would actually have some kind of working typestate system
<Drup>
how do you compose accross functions ?
<olle>
i don't even know what that means, lol
<olle>
but i'll get there. i hope :)
<Drup>
how do you make sure the composition is still safe according to your analysis ? :)
<Drup>
(it's the question to throw a wrench in many static analysis plans ... :p)
<olle>
Drup: well, my thought was simply that if the variable doesn't escape, it's automatically transfered ownership
<olle>
if and if does escape, it does not transfer
<olle>
and changing typestate is only allowed if you own the variable
<olle>
and, system only tracks ownership of classes you tag, like `@track-ownership`.
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<olle>
12:05 < olle> and changing typestate is only allowed if you own the variable
<olle>
But this can bite you
<olle>
like, "why don't I own it???"
<olle>
and you have to look in other places in the code to see what you did wrong.
<olle>
(not sure if that answers your question)
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<olle>
hm, I thought there would be more connections between ownership and escape analysis? maybe not
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