jan kili (Jan 07 2022 at 05:31): jan kili (Jan 07 2022 at 05:31):Happy to make an issue for this, but I just want a sanity check - does this make sense to anyone?
jan kili (Jan 07 2022 at 05:31):Module A:
main =
_ <- await (line "")
double = \x -> x * 2
doubleBind = \x -> (\_ -> double x)
six = (doubleBind 3) {}
line (Num.toStr six)
Output A:
6
Module B:
main =
_ <- await (line "")
double = \x -> x * 2
doubleBind = \x -> (\_ -> double x)
doubleThree = doubleBind 3
six = doubleThree {}
line (Num.toStr six)
Output B:
thread 'main' panicked at 'internal error: entered unreachable code: symbol/layout `8.IdentId(8)` ProcLayout { arguments: [Struct([]), LambdaSet(LambdaSet { set: [(`8.IdentId(8)`, [Builtin(Int(I64))])], representation: Struct([Builtin(Int(I64))]) })], result: Builtin(Int(I64)) } combo must be in DeclarationToIndex', compiler/mono/src/borrow.rs:227:9
Changed lines:
six = (doubleBind 3) {}
vs.
doubleThree = doubleBind 3
six = doubleThree {}
(I've removed roc/examples/cli/platform boilerplate for succinctness)
jan kili (Jan 07 2022 at 05:34):Is there an obvious reason that defining doubleThree causes a panic? roc check is clean on both, btw.
Brian Carroll (Jan 07 2022 at 06:52):That looks like a compiler bug. The panic is in a file related to refcount insertion. That phase comes after type checking, so wouldn't show up in roc check.
jan kili (Jan 07 2022 at 06:52):Thanks! I'll report it and temporarily modify my code to use an anonymous binding/closure :)
Brian Carroll (Jan 07 2022 at 06:53):Great!
jan kili (Jan 07 2022 at 06:54):That's a relief - I was worried that I'd messed up some great-grandchild binding in my confusing code... but by the time I boiled it down to the minimal reproduction above I was half-sure that something fishy was going on.
jan kili (Jan 07 2022 at 06:58):https://github.com/rtfeldman/roc/issues/2322
David Rojas Camaggi (Jan 10 2022 at 01:52):HI all, I am trying to set up my m1 mac for development with nix (using rosetta. i.e. platform is still x86_64). I am getting the following error
CMake Error at /nix/store/gxqi9sjvvwmf86qx075alg376x32s0zc-llvm-7.1.0-dev/lib/cmake/llvm/TableGen.cmake:14 (message):
LLVM_TABLEGEN_EXE not set
Call Stack (most recent call first):
include/clang/Driver/CMakeLists.txt:2 (tablegen)
Also tried with UTM and nix-shell also fails on aarch64 (different error), next week I will try another VM on x86 which would be slower but perhaps easier to set up.
I wonder if anyone has experience to share on M1 macs with nix (macos) or nixos.
Brendan Hansknecht (Jan 10 2022 at 03:17):I use an m1 mac with nix. No rosetta
Brendan Hansknecht (Jan 10 2022 at 03:17):Tends to just work
Brendan Hansknecht (Jan 10 2022 at 03:17):Though has some limitations were we don't fully support arm. Not a problem for the main llvm backend.
David Rojas Camaggi (Jan 10 2022 at 03:47):something must be off on my setup, this is what I get with system = aarch64-darwin -> " >...libredirect.dylib' (mach-o file, but is an incompatible architecture (have 'arm64', need 'arm64e'))"
Brendan Hansknecht (Jan 10 2022 at 04:29):I have never seen that, when does it come up?
Brendan Hansknecht (Jan 10 2022 at 04:29):Also, my setup may be leaky (i.e, I also have rust outside of nix and maybe zig), which may fix potential nix issues
David Rojas Camaggi (Jan 10 2022 at 05:38):found it was OpenAL (audio fw specific to macos), not sure why yet but commenting it out allows me to run a shell
David Rojas Camaggi (Jan 10 2022 at 05:41):doing that on x86 system, but that arm64 thing is from when I was trying aarch64-darwin
Lucas Rosa (Jan 11 2022 at 16:34):I use the M1 Max and no nix
jan kili (Jan 13 2022 at 06:48):How can I write a function that accepts a tag argument that could be either an A tag or a B tag? I tried this, but it doesn't work:
» a : [ A Str ]
… a = A "A"
… f : [ A Str, B Str ] -> Str
… f = \x ->
… when x is
… A y -> y
… B y -> y
… f a
── TYPE MISMATCH ───────────────────────────────────────────────────────────────
The 1st argument to f is not what I expect:
11│ f a
^
This a value is a:
[ A Str ]
But f needs the 1st argument to be:
[ A Str, B Str ]
Tip: Looks like a closed tag union does not have the B tag.
Tip: Closed tag unions can't grow, because that might change the size
in memory. Can you use an open tag union?
Yeah I've run into this kind of thing as well. It's because of the language supporting open tag unions. So in theory A Str could be part of any other union besides this one. Longer term I imagine we'll be able to figure it out, I'm not sure. But we don't right now.
I have found a type annotation works in this kind of situation. If you give a name to your union like AorB : [A Str, B Str] and then give a a type annotation like a : AorB
Brian Carroll (Jan 13 2022 at 06:58):Or I suppose you could probably type it out again rather than naming it! But you'll probably want to name it anyway.
jan kili (Jan 13 2022 at 06:59):Interesting, so now I notice that the inferred type for a = A "A" is [ A Str ]*
jan kili (Jan 13 2022 at 06:59):This is confusing to me, because how could a ever accumulate additional tags in its union? It will only ever be that A tag.
Brian Carroll (Jan 13 2022 at 07:09):Yeah I agree and I suspect that it's more of a bug than a feature. But I don't work on that part of the compiler so I'm not 100% sure!
jan kili (Jan 13 2022 at 07:10):Is the real meaning more like "a can be used anywhere a tag union matches this pattern: [ A Str ]*"?
jan kili (Jan 13 2022 at 07:12):I was initially interpreting its inferred type as saying "a is a tag could be A Str or something else"
jan kili (Jan 13 2022 at 07:12):That's what I gathered from this part of the tutorial:
If you have a closed union, that means it has all the tags it ever will, and can't accumulate more.
If you have an open union, that means it can accumulate more tags through conditional branches.
Brian Carroll (Jan 13 2022 at 07:12):Hold on, that's not the type of a! There's no *
Brian Carroll (Jan 13 2022 at 07:13):In your example code
jan kili (Jan 13 2022 at 07:13):True, but in the REPL if I drop my manual annotation, I get this:
The rockin’ roc repl
────────────────────────
Enter an expression, or :help, or :exit/:q.
» a = A "A"
… a
A "A" : [ A Str ]*
»
So it's a closed union that says a can only be A Str and never any other tag. So that's a different type.
jan kili (Jan 13 2022 at 07:13):The "inferred" type
Brian Carroll (Jan 13 2022 at 07:13):yes but your two examples have different types for the same expression
Brian Carroll (Jan 13 2022 at 07:15):The inferred type will have a * but if you annotate it without one you are telling the compiler you explicitly do not want any other tag to be a valid part of the type of a.
jan kili (Jan 13 2022 at 07:15):I see, so basically if a function can handle multiple tags, it's illegal to call it with an input that can't be all of those tags.
jan kili (Jan 13 2022 at 07:17):i.e. if I have an HTTP response that is somehow guaranteed to be a 404, I can't pass that to a function that processes both 200 and 404 responses?
Brian Carroll (Jan 13 2022 at 07:17):That very much depends on the types they have!
Brian Carroll (Jan 13 2022 at 07:18):There are lots of ways to represent HTTP responses in the type system
Brian Carroll (Jan 13 2022 at 07:19):Do you still get this error in the repl case with the inferred type?
jan kili (Jan 13 2022 at 07:19):No, I actually get a panic :laughing:
jan kili (Jan 13 2022 at 07:20):But that's probably irrelevant https://github.com/rtfeldman/roc/issues/2344
Brian Carroll (Jan 13 2022 at 07:20)::laughing:
jan kili (Jan 13 2022 at 07:20):Could you please give me an example of a situation where I would want to manually annotate a def as being a closed tag union instead of an open one?
jan kili (Jan 13 2022 at 07:20):a : [ A Str ]
a = A "A"
vs.
a : [ A Str ]*
a = A "A"
The bottom one seems objectively better, if the top one can't be passed to functions that accept other tags.
jan kili (Jan 13 2022 at 07:22):I ask because I'm still confused what the distinction is. I get why functions would accept closed vs. open, but I don't get how a def can BE closed or open.
Brian Carroll (Jan 13 2022 at 07:22):I don't know, I didn't design this feature, I was just trying to help with your specific error but you probably want to talk to someone who was involved in designing it
jan kili (Jan 13 2022 at 07:22)::) Makes sense, thanks!
jan kili (Jan 13 2022 at 07:23):I'll open a new topic for this, since you helped me figure out the silly thing.
jan kili (Jan 16 2022 at 08:17):I modified the example CLI platform to use Rust's print instead of println, and now I'm successfully writing a lot of Rust-based prints to stdout (with a \r between each, so that the line overwrites itself)! However, after ~47,000 consecutive (very fast) writes to stdout, I'm getting a Segmentation fault: 11. Since these writes are generated by recursive _ <- await ... calls, is this an expected "stack overflow"-type problem with having too many callbacks? Is there a better way to do a lot of I/O tasks without causing such a segfault? My instinct is to replace the recursion with a while loop, but that doesn't exist in Roc.
jan kili (Jan 16 2022 at 08:25):The only way I can think to get more writes out of this program would be to wrap the Roc main function in a Rust while loop at the platform level (and make the Roc main function responsible for only one write), but I don't know enough about platforms to know if that would somehow break the platform/application contract.
jan kili (Jan 16 2022 at 08:31):The context for this I/O use case is that I'm experimenting with how one might use Roc to do ASCII animation for things like CLI loading spinners or simple CLI games (Snake? Space Invaders?) :smile:
Brian Carroll (Jan 16 2022 at 11:25):I can help with one piece of this: Getting the compiler to generate while loops.
Any function that is tail-recursive will be automatically transformed into a while loop. If you're not familiar with that concept, here's an article that explains it: https://www.geeksforgeeks.org/tail-recursion/. Normally you need to refactor your code so that any value that's preserved from one iteration to the next becomes an argument of the recursive call. Those extra arguments usually make the function ugly to use from the outside world, so you end up wrapping it in another function to make it nicer.
jan kili (Jan 16 2022 at 12:44):Ah, that's super useful! Does that only apply to functions provided to the platform, or all of them?
jan kili (Jan 16 2022 at 13:33):@Brian Carroll Would this module get the while loop optimization? It seems like it might, as it is still running and hasn't crashed yet :smiley:
#!/usr/bin/env roc
app "example"
packages { pf: "./roc/examples/cli/platform" }
imports [ pf.Stdout.{ line }, pf.Task.{ await } ]
provides [ main ] to pf
main =
_ <- await (line "")
tick 1000000000000
tick = \count ->
if count == 0 then
line "Done!"
else
# _ <- await (line (Num.toStr count))
tick (count - 1)
Nope, it's any function that calls itself and immediately returns the result. This is an optimisation that is implemented in pretty much every functional language. It's the standard trick for doing loops without mutation. I think it was figured out in the 70s, like everything else! It's called tail-call optimisation or tail-call elimination.
Brian Carroll (Jan 16 2022 at 13:43):I had lots of fun learning to use this when I discovered it!
Folkert de Vries (Jan 16 2022 at 13:52):eh, in the above case tick will be TCO'd
jan kili (Jan 16 2022 at 14:15):Would uncommenting the await change that?
Folkert de Vries (Jan 16 2022 at 14:18):today, probably yes
Folkert de Vries (Jan 16 2022 at 14:18):but LLVM may be able to turn the recursion back into a loop after some inlining
jan kili (Jan 16 2022 at 14:50):I see! Thanks. So then... is it impossible today to avoid a stack overflow when infinitely-repeating an I/O cycle?
jan kili (Jan 16 2022 at 14:57):(I'm glad there's a path to clean TCO for I/O, though!)
Folkert de Vries (Jan 16 2022 at 20:30):This is actually an interesting question. So say we start with something of this form
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
Effect.await (Effect.putLine "step") \{} -> tick (count - 1)
Where Effect a : [ @Effect (World -> { a, world: World } ) ] and
Effect.await : Effect a, (a -> Effect b) -> Effect b
Effect.await = \@Effect thunk, toEffect ->
@Effect \world1 ->
{ a, world: world2 } = thunk world1
@Effect thunk2 = toEffect a
thunk2 world2
Inlining gives
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
@Effect thunk = Effect.putLine "step"
toEffect = \{} -> tick (count - 1)
@Effect \world1 ->
{ a, world: world2 } = thunk world1
@Effect thunk2 = toEffect a
thunk2 world2
The @Effect wrapper melts away
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
thunk = Effect.putLine "step"
toEffect = \{} -> tick (count - 1)
\world1 ->
{ a, world: world2 } = thunk world1
thunk2 = toEffect a
thunk2 world2
We can clean this up slightly
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
thunk = Effect.putLine "step"
toEffect = \{} -> tick (count - 1)
\world1 ->
{ a, world: world2 } = thunk world1
(toEffect a) world2
In this case we can inline toEffect, because the data dependency on world2 ensures correct evaluation order
Also we can move thunk into the closure and inline it (this does not happen today, but it's semantically valid)
tick : I64 -> (World -> { a: {}, world : World })
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
\world1 ->
{ a: _, world: world2 } = (Effect.putLine "step") world1
(tick (count - 1)) world2
now we lift functions to the toplevel, and run into issues with closures
helper \world1, { count } ->
{ a: _, world: world2 } = (Effect.putLine "step") world1
(tick (count - 1)) world2
tick : I64 -> (World -> { a: {}, world : World })
tick = \count ->
if count == 0 then
Effect.putLine "done"
else
helper ??? { count }
we need to complete the closure conversion
helper : World, { count : I64 } -> { a: {}, world : World }
helper \world1, { count } ->
{ a: _, world: world2 } = (Effect.putLine "step") world1
when tick (count - 1) is
C1 { msg } -> (Effect.putLine msg) world2
C2 { count } -> helper world2 { count }
tick : I64 -> [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ]
tick = \count ->
if count == 0 then
C1 { msg: "done" }
else
C2 { count }
and now helper can be TCO'd.
Folkert de Vries (Jan 16 2022 at 20:31):given that we can do this with some simple rewriting, it seems plausible that LLVM could already figure this out today
Folkert de Vries (Jan 16 2022 at 20:34):indeed, for this example the LLVM gets there
%call1.i.i = tail call fastcc %str.RocStr @"#UserApp_tick_6cc39a125db7a4f2ba7ee17ffefa9ff1fe97baed9c849631614587aef96caa15"(i64 %operation_result.i.i.i)
ret %str.RocStr %call1.i.i
🤯
jan kili (Jan 16 2022 at 21:19)::bow:
jan kili (Jan 16 2022 at 21:28):How does tick not need to call helper?
How is its annotation (tick : I64 -> [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ]) legal if Effect.putLine and helper are functions?
Are the functions called implicitly or something?
Folkert de Vries (Jan 16 2022 at 21:38):trying to figure out how to explain this, but that's kind of the idea yes
Folkert de Vries (Jan 16 2022 at 21:45):We're missing main here
main : Effect {}
main = tick 5
Based on the return type for tick, this should be
main : [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ]
main = tick 5
This is the main function we expose. What it returns is really a suspended computation, or a recipe for a computation. We also expose an evaluator for this recipe. Intuitively
cheatyActualMain : Effect a -> a
cheatyActualMain = \effect ->
@Effect thunk = effect
thunk world
The closure transform turns that into (we're pretending here that cheatyActualMain main is called:
cheatyActualMain : [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ] -> {}
cheatyActualMain = \closure ->
when closure is
C1 { msg } -> (Effect.putLine msg) world
C2 { count } -> helper world { count }
Where is World defined? (I've never heard of "worlds" in Roc before.)
Folkert de Vries (Jan 16 2022 at 21:49):it's something I stole from haskell real quick to make sure the ordering of operations is fixed
Folkert de Vries (Jan 16 2022 at 21:49):you could say World : {}
Folkert de Vries (Jan 16 2022 at 21:49):haskell's IO monad is defined in this way
jan kili (Jan 16 2022 at 21:50):How does Effect a unify with [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ]? (I may be using the world "unify" incorrectly here, but I don't see how cheatyActualMain can accept main as its argument.
Folkert de Vries (Jan 16 2022 at 21:50):where IO a : (RealWorld -> (a, RealWorld)
Folkert de Vries (Jan 16 2022 at 21:51):right, so they don't unify but they are related in this case
Folkert de Vries (Jan 16 2022 at 21:51):in e.g. elm we think of function types as just a -> b
Folkert de Vries (Jan 16 2022 at 21:52):but, we extend that with an extra piece of information: what values (and with which types) are captured by the function
Folkert de Vries (Jan 16 2022 at 21:53):So given
identity = \x -> x
where elm would say
identity : a -> a
we under the hood say
identity : a [ C identity {} ] -> a
Whoa! So is [ C1 Effect.putLine { msg: Str }, C2 helper { count: I64 } ] an annotation for only under-the-hood or is it also legal above-the-hood?
Folkert de Vries (Jan 16 2022 at 21:54):and more interestingly
f = \x -> Str.concat x y
(note, y is not bound within f, it is a free variable, and captured by this closure)
f : Str [ C f { y : Str } ] -> Str
the closure part is under-the-hood entirely
jan kili (Jan 16 2022 at 21:54):I'm wondering whether I can stitch these code snippets into a module and run it on ./roc/examples/cli/platform
Folkert de Vries (Jan 16 2022 at 21:56):in any case, to bring this together, we eliminate function values, and replace them by their captured environment. So main : Effect a really has a function type main : World [ some things ] -> { a, World }, and that function value we represent by the closure tag union
Folkert de Vries (Jan 16 2022 at 21:58):and then by doing some bookkeeping we can later know how to evaluate a closure value: simply match on all possible functions that it could be and pass along the arguments
jan kili (Jan 16 2022 at 22:09):Are these tricks possible in a simple application outside of its platform? Above the platform/application boundary?
jan kili (Jan 16 2022 at 22:10):For example, using the examples/cli/platform as-is?
Folkert de Vries (Jan 16 2022 at 22:10):not in user code, because Effect is made with a private tag
Folkert de Vries (Jan 16 2022 at 22:10):so you cannot unpack it or manually make an Effect from a function
jan kili (Jan 16 2022 at 22:16):Ah, I see. Does that mean that today there's no platform-agnostic way to avoid a stack overflow when infinitely-repeating an I/O cycle?
Folkert de Vries (Jan 16 2022 at 22:17):there is no guaranteed way
jan kili (Jan 16 2022 at 22:17):Platforms have to explicitly support any infinite loops required for servers / games / long-running processes?
Folkert de Vries (Jan 16 2022 at 22:17):but with --optimize tail optimization already happens
Folkert de Vries (Jan 16 2022 at 22:18):in these cases
Folkert de Vries (Jan 16 2022 at 22:19):I'd like to add Effect.forever : Effect a -> Effect b for that
jan kili (Jan 16 2022 at 22:22):Thank you for all this info!
jan kili (Jan 16 2022 at 22:23):I'm disappointed that my pure-Roc CLI-based ASCII game hopes must be put on hold, but I'm hopeful it'll get support in the future :)
Folkert de Vries (Jan 16 2022 at 22:23):did you run into stack issues?
jan kili (Jan 16 2022 at 22:23):Yeah, I got a segfault after 47k frames
Folkert de Vries (Jan 16 2022 at 22:23):ah, ok
Folkert de Vries (Jan 16 2022 at 22:23):you did use --optimize?
jan kili (Jan 16 2022 at 22:24):I didn't! What command is that a flag for?
Folkert de Vries (Jan 16 2022 at 22:24):you can do cargo run -- --optimize foo/bar/Baz.roc
jan kili (Jan 16 2022 at 22:24):Ooh, I'll try
jan kili (Jan 16 2022 at 22:25):And that might work with a mid-tick _ <- await?
Folkert de Vries (Jan 16 2022 at 22:25):certainly worth a try
jan kili (Jan 16 2022 at 22:48):
Folkert de Vries (Jan 16 2022 at 22:49):nice!
Folkert de Vries (Jan 16 2022 at 22:49):so yeah we should figure out how to also make this work in non-optimized modes
jan kili (Jan 16 2022 at 22:50):Am I doing something silly? Yes, I'm running unoptimized code!
jan kili (Jan 16 2022 at 22:50):Space Invaders, here I come.
jan kili (Jan 16 2022 at 22:56):Thank you!
jan kili (Jan 16 2022 at 22:58):(Side note, my mac went to sleep twice during the one minute I was running that infinite sleepless loop :joy:)
jan kili (Jan 16 2022 at 22:59):(I think I might need to add a sleep function to the platform's API)
Folkert de Vries (Jan 16 2022 at 23:00):really, it can go to sleep during busy-waiting loops?
Pit Capitain (Jan 17 2022 at 07:17):Thank you both for this really interesting discussion :smile:
Brian Carroll (Jan 17 2022 at 10:24):Yeah, interesting stuff!
Brian Carroll (Jan 17 2022 at 10:25):Great we can do this as well. Having a main loop with I/O inside it will be useful in all sorts of places!
Richard Feldman (Jan 17 2022 at 17:28):I wonder if https://github.com/rtfeldman/roc/issues/1778 would still be reproducible with --optimize :thinking:
Folkert de Vries (Jan 17 2022 at 18:05):I think the inliner is not able to make the same thing happen there. We definitely tried it with --optimize
Folkert de Vries (Jan 19 2022 at 16:23):define internal fastcc {} @Effect_forever_inner_fb5e512425fc9449316ec95969ebe71e2d576dbab833d61e2a5b9330fd70ee2({} %"5", { { %str.RocStr } } %"#arg_closure") {
entry:
br label %tailrecurse
tailrecurse: ; preds = %tailrecurse, %entry
%"5.tr" = phi {} [ %"5", %entry ], [ zeroinitializer, %tailrecurse ]
%"#arg_closure.tr" = phi { { %str.RocStr } } [ %"#arg_closure", %entry ], [ %call1, %tailrecurse ]
%struct_field_access_record_0 = extractvalue { { %str.RocStr } } %"#arg_closure.tr", 0
tail call fastcc void @"#Attr_#inc_2"({ %str.RocStr } %struct_field_access_record_0, i64 1)
tail call fastcc void @"#Attr_#dec_3"({ { %str.RocStr } } %"#arg_closure.tr")
tail call fastcc void @"#Attr_#inc_2"({ %str.RocStr } %struct_field_access_record_0, i64 1)
%call = tail call fastcc {} @Effect_effect_closure_putLine_9d9f29527a6be626a8f5985b26e19b237b44872b03631811df4416fc1713178({} zeroinitializer, { %str.RocStr } %struct_field_access_record_0)
%call1 = tail call fastcc { { %str.RocStr } } @Effect_forever_67abdd721024f0ff4eb3f4c2fc13bc5bad42db7851d456d88d203d15aaa450({ %str.RocStr } %struct_field_access_record_0)
br label %tailrecurse
}
it's beautiful
Folkert de Vries (Jan 19 2022 at 16:24):This is an Effect.forever (used as e.g. Effect.forever (Effect.putLine "hello world") to print that line forever) and llvm turns it into a loop
Folkert de Vries (Jan 19 2022 at 16:26):still needs some cleanup, and then maybe some variations that could iterate while some condition is true
jan kili (Jan 19 2022 at 16:28):Nice! Is this for use in appcode or platformcode?
Folkert de Vries (Jan 19 2022 at 16:30):a platform author could now expose Task.forever building upon this function
Folkert de Vries (Jan 19 2022 at 16:30):so, both kinda
jan kili (Jan 19 2022 at 16:31):That's super useful.
Richard Feldman (Jan 19 2022 at 17:28):wow, fantastic!!! :heart_eyes:
this may end up becoming one of the most commonly used functions among all Roc programs!
Lucas Rosa (Jan 19 2022 at 19:53):omg! I wanted this for an event loop when I was trying to wrap SDL in a platform
Lucas Rosa (Jan 19 2022 at 19:53):this is very cool!
Folkert de Vries (Jan 19 2022 at 21:51):This now also works
main : Task.Task {} []
main =
Task.loop 0 looper
looper = \n ->
if n < 10 then
s = Num.toStr n
{} <- Task.after (Task.putLine "Iteration: \(s)")
Task.succeed (Step (n + 1))
else
Task.succeed (Done {})
plus we get
forever : Task val err -> Task * err
forever = \task ->
helper = \{} ->
task
|> Effect.map \res ->
when res is
Ok _ -> Step {}
Err e -> Done (Err e)
Effect.loop {} helper
i.e. a forever on tasks that terminates when a task fails
jan kili (Jan 19 2022 at 22:41):Yesss
jan kili (Jan 19 2022 at 22:42):Are you planning to add any of these examples to examples/?
jan kili (Jan 19 2022 at 22:43):This feature is invaluable to web servers, games, etc! Thank you :D
Folkert de Vries (Jan 19 2022 at 22:43):the loop and forever task functions are added to the benchmarks and cli platforms in my PRs
Folkert de Vries (Jan 19 2022 at 22:44):no usage examples yet though
jan kili (Jan 19 2022 at 22:45):I might add some usage examples (unless you want to)
jan kili (Jan 19 2022 at 22:46):to give examples/cli/Echo.roc some friends
Lucas Rosa (Jan 19 2022 at 23:44):this does make building a REPL in roc possible now
Lucas Rosa (Jan 19 2022 at 23:44):well I should say easier*
jan kili (Feb 13 2022 at 06:46):Should this cause an Eldritch horror to be unleashed on my REPL? :scared:
x : F32
x = 1.5
x * Num.toFloat 4
I'm thinking no: https://github.com/rtfeldman/roc/issues/2476 :laughing:
jan kili (Mar 12 2022 at 11:24):I'm back with more tag union panics! :laughing:
» x : [ Y U8 ]*
… x = Y 3
… x
thread '<unnamed>' panicked at 'invalid content in tag union variable: (114, RigidVar(SubsIndex<roc_module::ident::Lowercase>(0)))', compiler/mono/src/layout.rs:2002:23
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
^C
Am I doing something silly?
jan kili (Mar 12 2022 at 11:24):(a closed tag union works fine here)
» x : [ Y U8 ]
… x = Y 3
… x
Y 3 : [ Y U8 ]
I've got a second one! The silliness continues?
» wrap = \value -> Tag value
… wrap
<function> : a -> [ Tag a ]*
» wrap = \value -> Tag value
… wrapIt = wrap
… wrapIt
<function> : a -> [ Tag a ]*
» wrap = \value -> Tag value
… wrap 42
Tag 42 : [ Tag (Num *) ]*
» wrap = \value -> Tag value
… wrapIt = wrap
… wrapIt 42
thread 'main' panicked at 'Roc failed with message: "UnresolvedTypeVar compiler/mono/src/ir.rs line 6842"', repl_cli/src/lib.rs:137:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Could you file bugs for these? The second one is known I think but would be good to have a record of both!
jan kili (Jul 03 2022 at 04:43):Silliness detected? https://github.com/rtfeldman/roc/issues/3377
jan kili (Jul 03 2022 at 04:53):(I'm causing a segfault by substituting [0, 1, 2] with List.range 0 3)
jan kili (Jul 03 2022 at 05:22):I've encountered a second problem! Am I missing something about this syntax, because this seems like a reasonable recursion pattern to me:
» a = \b ->
… c = \d ->
… if d >= 10 then d else c (d+b)
… c 0
… a 6
thread 'main' panicked at 'internal error: entered unreachable code: symbol/layout `#UserApp.c` ProcLayout { arguments: [Builtin(Int(I64))], result: Builtin(Int(I64)) } combo must be in DeclarationToIndex', crates/compiler/mono/src/borrow.rs:165:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
[jan@framey roc]$
(btw, that inner function is fine by itself)
» c = \d ->
… if d >= 10 then d else c (d+3)
… c 0
12 : Num *
»
I'll go ahead and report that second "internal error" problem as an issue, too.
jan kili (Jul 03 2022 at 05:26):I expect that I'm exhibiting minimal silliness here today. Sorry for being boring!
jan kili (Jul 03 2022 at 05:31):https://github.com/rtfeldman/roc/issues/3378
jan kili (Jul 11 2022 at 16:41):Ummm what am I missing here?
main =
deck = myDeck
{card} = dealMe deck
rank =
when card.rank is
Ace -> "Ace"
King -> "King"
Queen -> "Queen"
Jack -> "Jack"
suit =
when card.suit is
Club -> "Clubs"
Diamond -> "Diamonds"
Heart -> "Hearts"
Spade -> "Spades"
"My card is the \(card.rank) of \(card.suit)!\n"
── MISSING EXPRESSION ─ ..._roc/domain-modeling-in-roc/step_2__card_game_A.roc ─
I am partway through parsing a definition, but I got stuck here:
4│ provides [main] to pf
...
23│ main =
24│ deck = myDeck
25│ {card} = dealMe deck
26│ rank =
27│ when card.rank is
^
I was expecting to see an expression like 42 or "hello".
:thinking:
Brendan Hansknecht (Jul 11 2022 at 16:44):Whitespace bug? That is definitely what it looks like to me.
jan kili (Jul 11 2022 at 16:45):Ooh, I'll check for that
Brendan Hansknecht (Jul 11 2022 at 16:46):Might be worth running roc format and seeing the diff? might fix it?
jan kili (Jul 11 2022 at 16:47):Success!
jan kili (Jul 11 2022 at 16:47):I didn't try the formatter, but I think it was a funky newline.
jan kili (Jul 11 2022 at 16:47):Thank you :)
Brendan Hansknecht (Jul 11 2022 at 16:48):If it seems worth tracking/filing an issue, maybe we can make a better error message or fix the parsing around this.
jan kili (Jul 11 2022 at 16:50):While I have you here, any tips for this?
[jan@framey roc]$ export RUST_BACKTRACE=full
[jan@framey roc]$ cargo run ../domain-modeling-in-roc/step_2__card_game_A.roc
Finished dev [unoptimized + debuginfo] target(s) in 0.44s
Running `target/debug/roc ../domain-modeling-in-roc/step_2__card_game_A.roc`
thread '<unnamed>' panicked at 'not yet implemented', crates/compiler/mono/src/ir.rs:2382:23
stack backtrace:
0: 0x5635ba31fb9d - std::backtrace_rs::backtrace::libunwind::trace::hee598835bc88d35b
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x5635ba31fb9d - std::backtrace_rs::backtrace::trace_unsynchronized::h9cdc730ba5cf5d72
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x5635ba31fb9d - std::sys_common::backtrace::_print_fmt::h75aeaf7ed30e43fa
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:66:5
3: 0x5635ba31fb9d - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h606862f787600875
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:45:22
4: 0x5635ba34aadc - core::fmt::write::he803f0f418caf762
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/fmt/mod.rs:1190:17
5: 0x5635ba319d28 - std::io::Write::write_fmt::h70bc45872f37e7bb
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/io/mod.rs:1657:15
6: 0x5635ba321dd7 - std::sys_common::backtrace::_print::h64d038cf8ac3e13e
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:48:5
7: 0x5635ba321dd7 - std::sys_common::backtrace::print::h359300b4a7fccf65
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:35:9
8: 0x5635ba321dd7 - std::panicking::default_hook::{{closure}}::hf51be35e2f510149
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:295:22
9: 0x5635ba321aa0 - std::panicking::default_hook::h03ca0f22e1d2d25e
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:314:9
10: 0x5635ba322529 - std::panicking::rust_panic_with_hook::h3b7380e99b825b63
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:698:17
11: 0x5635ba3221d9 - std::panicking::begin_panic_handler::{{closure}}::h8e849d0710154ce0
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:586:13
12: 0x5635ba320064 - std::sys_common::backtrace::__rust_end_short_backtrace::hedcdaddbd4c46cc5
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:138:18
13: 0x5635ba321f29 - rust_begin_unwind
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:584:5
14: 0x5635b5b4ae83 - core::panicking::panic_fmt::he1bbc7336d49a357
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/panicking.rs:143:14
15: 0x5635b5b4ad4d - core::panicking::panic::h4241c5ccea17faca
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/panicking.rs:48:5
16: 0x5635b99cc490 - roc_mono::ir::from_can_let::he631a1fd2e7f1db7
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2382:23
17: 0x5635b9a09970 - roc_mono::ir::from_can::h6c53f19073fb59f4
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:5932:33
18: 0x5635b996e417 - roc_mono::ir::from_can_let::{{closure}}::hb169aff3d0732e09
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2206:25
19: 0x5635b99769d7 - roc_mono::ir::handle_variable_aliasing::h457631afa9a49d05
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:7025:16
20: 0x5635b99d0e75 - roc_mono::ir::from_can_let::he631a1fd2e7f1db7
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2209:24
21: 0x5635b9a09970 - roc_mono::ir::from_can::h6c53f19073fb59f4
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:5932:33
22: 0x5635b99d6413 - roc_mono::ir::specialize_external::h014c8ba65786d364
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2988:32
23: 0x5635b996ebf8 - roc_mono::ir::specialize_variable_help::hc0e86a21717b3946
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:3465:23
24: 0x5635b99dbbf3 - roc_mono::ir::specialize_variable::h0634205863a1b1ec
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:3414:5
25: 0x5635b99d4cb4 - roc_mono::ir::specialize_external_help::he85ecfa478515205
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2767:33
26: 0x5635b99d4aa2 - roc_mono::ir::specialize_external_specializations::h03afe44495a518a6
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2740:13
27: 0x5635b99d400e - roc_mono::ir::specialize_all::h38efe702f28bba33
at /home/jan/_code/_roc/roc/crates/compiler/mono/src/ir.rs:2673:9
28: 0x5635b7436e4e - roc_load_internal::file::make_specializations::h624990574ec76565
at /home/jan/_code/_roc/roc/crates/compiler/load_internal/src/file.rs:4519:13
29: 0x5635b743c47b - roc_load_internal::file::run_task::h6036f07fd619b017
at /home/jan/_code/_roc/roc/crates/compiler/load_internal/src/file.rs:4996:17
30: 0x5635b741559a - roc_load_internal::file::worker_task::hebe41c651db0920e
at /home/jan/_code/_roc/roc/crates/compiler/load_internal/src/file.rs:1817:34
31: 0x5635b7440e1a - roc_load_internal::file::load_multi_threaded::{{closure}}::{{closure}}::h16d5eba0a83616fc
at /home/jan/_code/_roc/roc/crates/compiler/load_internal/src/file.rs:1659:25
32: 0x5635b744caf7 - crossbeam_utils::thread::ScopedThreadBuilder::spawn::{{closure}}::ha411c1ac2e878ff5
at /home/jan/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-utils-0.8.10/src/thread.rs:438:31
33: 0x5635b73d3fef - core::ops::function::FnOnce::call_once{{vtable.shim}}::h182bc693cee28e90
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/ops/function.rs:227:5
34: 0x5635b740505d - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hee34075471a3830c
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/alloc/src/boxed.rs:1853:9
35: 0x5635b74eed84 - std::sys_common::backtrace::__rust_begin_short_backtrace::h74784c32857fa8b7
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys_common/backtrace.rs:122:18
36: 0x5635b74dd8d4 - std::thread::Builder::spawn_unchecked_::{{closure}}::{{closure}}::h54bd13ac090e0e91
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/thread/mod.rs:498:17
37: 0x5635b74efaa4 - <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::he1cf1df6def34f88
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/panic/unwind_safe.rs:271:9
38: 0x5635b74ef26d - std::panicking::try::do_call::h48b63b9234108830
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:492:40
39: 0x5635b74ef49b - __rust_try
40: 0x5635b74ef1bd - std::panicking::try::hb3ba778589fab460
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panicking.rs:456:19
41: 0x5635b74ec7d4 - std::panic::catch_unwind::h7c5138398b54d137
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/panic.rs:137:14
42: 0x5635b74dd6f3 - std::thread::Builder::spawn_unchecked_::{{closure}}::hd3349d142c8673c4
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/thread/mod.rs:497:30
43: 0x5635b73d3f0f - core::ops::function::FnOnce::call_once{{vtable.shim}}::h14f5d8c93db30fba
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/core/src/ops/function.rs:227:5
44: 0x5635ba329d03 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hf70ac038171e3e1a
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/alloc/src/boxed.rs:1853:9
45: 0x5635ba329d03 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he6690128792365ad
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/alloc/src/boxed.rs:1853:9
46: 0x5635ba329d03 - std::sys::unix::thread::Thread::new::thread_start::ha07928d93d5a5ec9
at /rustc/7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c/library/std/src/sys/unix/thread.rs:108:17
47: 0x7f8513f29d40 - start_thread
48: 0x7f8513a8703f - __GI___clone
49: 0x0 - <unknown>
^C
[jan@framey roc]$
does it pass roc check?
Brendan Hansknecht (Jul 11 2022 at 16:51):That catches a lot that might crash the compiler.
jan kili (Jul 11 2022 at 16:51):GAH I always forget to go back to checking
jan kili (Jul 11 2022 at 16:52):I do check check check check, then the first time it passes I go straight to run run run run while editing :facepalm:
jan kili (Jul 11 2022 at 16:52):Thanks again, check has my answers :)
Richard Feldman (Jul 11 2022 at 16:53):that's surprising actually - cargo run should do the "check and then only run if there are no errors reported" flow :thinking:
Richard Feldman (Jul 11 2022 at 16:53):so I'm surprised that cargo run ../domain-modeling-in-roc/step_2__card_game_A.roc would report no compile-time errors but cargo run check would!
Brendan Hansknecht (Jul 11 2022 at 16:59):really? I thought cargo run <script> and roc <script> did not run check. That would definitely be useful.
Richard Feldman (Jul 11 2022 at 16:59):so roc foo.roc does this, but roc run foo.roc just runs and doesn't check
Brendan Hansknecht (Jul 11 2022 at 16:59):hmm. Yeah, I don't think that is working
Richard Feldman (Jul 11 2022 at 16:59):so it's the difference between cargo run run and cargo run :big_smile:
Brendan Hansknecht (Jul 11 2022 at 17:00):Or maybe it does part of the check but not all of it...not sure
Brendan Hansknecht (Jul 11 2022 at 17:00):I definitely need to use check still.
Richard Feldman (Jul 11 2022 at 17:00):hm, if you can reproduce an example of it not working right, maybe it's an easy fix!
jan kili (Jul 25 2022 at 01:24):Hello, it's me again, Dr. Help I. M. Crashing :laughing:
jan kili (Jul 25 2022 at 01:24):This behavior seems like it shouldn't be possible, unless there's a bug in the release build process:
[jan@framey ~]$ cd ~/_code/_roc/roc
[jan@framey roc]$
[jan@framey roc]$ nix develop
[jan@framey roc]$
[jan@framey roc]$ cargo run ../project-euler-in-roc/2.roc
Finished dev [unoptimized + debuginfo] target(s) in 0.46s
Running `target/debug/roc ../project-euler-in-roc/2.roc`
🔨 Rebuilding host...
4613732
[jan@framey roc]$
[jan@framey roc]$ cargo build --release
Finished release [optimized] target(s) in 0.48s
[jan@framey roc]$
[jan@framey roc]$ exit
exit
[jan@framey roc]$
[jan@framey roc]$ cd ~/_code/_roc/project-euler-in-roc/
[jan@framey project-euler-in-roc]$
[jan@framey project-euler-in-roc]$ ../roc/target/release/roc 2.roc
🔨 Rebuilding host...
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', crates/compiler/build/src/link.rs:360:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Any { .. }', crates/cli/src/build.rs:283:46
[jan@framey project-euler-in-roc]$
[jan@framey project-euler-in-roc]$ ../roc/target/release/roc check 2.roc
0 errors and 0 warnings found in 20 ms.
[jan@framey project-euler-in-roc]$
[jan@framey project-euler-in-roc]$ ???
It seems to not matter which app I run, the same "yes inside nix develop, no outside it" happens
jan kili (Jul 25 2022 at 01:26):Did I miss a step? (I remembered to check this time! haha)
jan kili (Jul 25 2022 at 01:28):(on Linux, Fedora 36)
jan kili (Jul 25 2022 at 01:56):Oh, and I guess this is additional info + a more concise repro:
[jan@framey roc]$ ./target/release/roc ../project-euler-in-roc/2.roc
🔨 Rebuilding host...
4613732
[jan@framey roc]$
[jan@framey roc]$ exit
exit
[jan@framey roc]$
[jan@framey roc]$ cd ../project-euler-in-roc/
[jan@framey project-euler-in-roc]$
[jan@framey project-euler-in-roc]$ ../roc/target/release/roc 2.roc
🔨 Rebuilding host...
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', crates/compiler/build/src/link.rs:360:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Any { .. }', crates/cli/src/build.rs:283:46
[jan@framey project-euler-in-roc]$
Summary:
cargo run myApp.roc works inside nix developcargo build --release works inside nix developtarget/release/roc myApp.roc works inside nix developtarget/release/roc myApp.roc panics outside nix develop jan kili (Jul 25 2022 at 01:59):I thought builds were self-contained, but are they not?
Brendan Hansknecht (Jul 25 2022 at 02:45):Your missing zig on your machine?
Brendan Hansknecht (Jul 25 2022 at 02:45):*line 360 not 310, so clang
Brendan Hansknecht (Jul 25 2022 at 02:45):You can't build the platform
Brendan Hansknecht (Jul 25 2022 at 02:46):If you were to build in nix and then build outside of nix with --precompiled-host=true, it should work.
Brendan Hansknecht (Jul 25 2022 at 02:48):We should improve those error messages
jan kili (Jul 25 2022 at 02:50)::check: Wow, that was fast.
[jan@framey project-euler-in-roc]$ ../roc/target/release/roc 2.roc --precompiled-host=true
4613732
[jan@framey project-euler-in-roc]$
I didn't know about that flag, and I assumed a Roc build could compile platforms/hosts without any system dependencies!
Brendan Hansknecht (Jul 25 2022 at 02:52):The host is still in another language, so that has all the dependencies that other language brings in. Long term, you should be able to just download the package as a precompiled host. Once that is the norm, all the host building shouldn't matter to anyone except platform authors.
jan kili (Jul 25 2022 at 02:55):Nice! So right now, the --precompiled-host=true tells the Roc executable to look in the platform dir for a platform executable?
jan kili (Jul 25 2022 at 02:56):Should the word "host" be replaced with "platform" in all app-developer-facing messaging?
Brendan Hansknecht (Jul 25 2022 at 02:57):It basically says, trust me, the platform was already compiled and has not changed. Don't spawn the thread that compiles the platform. We will use the existing executable file.
Brendan Hansknecht (Jul 25 2022 at 03:00):And probably to the host vs platform question. It is a terminology thing that has turned into them essentially being used interchangeably (though there is technically a difference). Platform is definitely the term I would expect an app author to see and use.
jan kili (Jul 25 2022 at 03:00):Great! Thank you very much for these great explanations :)
jan kili (Jul 25 2022 at 03:02):This will definitely become part of my workflow:
[jan@framey project-euler-in-roc]$ alias roc='../roc/target/release/roc --precompiled-ho
st=true'
[jan@framey project-euler-in-roc]$ roc 2.roc
4613732
[jan@framey project-euler-in-roc]$
Regarding host vs. platform: https://github.com/rtfeldman/roc/issues/3630
jan kili (Jul 25 2022 at 03:12):Regarding panic/error messaging: https://github.com/rtfeldman/roc/issues/3631
Brian Carroll (Jul 25 2022 at 04:01):On terminology: The platform consists of a non-Roc "host" and a Roc API to interface to it.
Brian Carroll (Jul 25 2022 at 04:05):So the message is referring to technically the right thing, but using a term that isn't explained anywhere in the docs yet.
Brendan Hansknecht (Jul 25 2022 at 04:10):Sure, but to a roc app author, they will only ever interact with platforms as a unit, never the host directly. So flags and error messages should generally be catered to that?
Brendan Hansknecht (Jul 25 2022 at 04:10):At least that is my thought
Brian Carroll (Jul 25 2022 at 04:13):I wasn't disagreeing, just explaining to anyone following who didn't know.
jan kili (Jul 25 2022 at 04:14):Nice, does that API include only .roc files?
Brian Carroll (Jul 25 2022 at 04:19):Yes
jan kili (Oct 05 2022 at 02:59):How do I bool?
|> List.map (\sum ->
when sum * 2 > rowCount is
Bool.true -> 1
_ -> 0)
── SYNTAX PROBLEM ──────────────────────────────────────── day_3_solutions.roc ─
This pattern is malformed:
37│ Bool.true -> 1
^^^^^^^^^
It works as an if ... then ... else ... expression but not a when ... is ... expression
jan kili (Oct 05 2022 at 03:06):I'll just switch it to if/else
jan kili (Oct 05 2022 at 03:07):Dang functional programming... making me forget about good old-fashioned if/else... :angry_cat: :laughing:
Richard Feldman (Oct 05 2022 at 03:17):oh yeah, this is supposed to work exactly the way you tried to write it - it just hasn't been implemened yet :sweat_smile:
Richard Feldman (Oct 05 2022 at 03:18):Foo.bar -> ... should desugar to essentially x if x == Foo.bar -> ...
Richard Feldman (Oct 05 2022 at 03:19):which you can always write by hand, but yes - in the case of booleans specifically, might as well use if! :big_smile:
jan kili (Oct 05 2022 at 03:19):Any hope for [a, b, c] -> ...? :fingers_crossed: :present: :santa:
jan kili (Oct 05 2022 at 03:20):Maybe tuples will alleviate that need
Richard Feldman (Oct 05 2022 at 03:23):yeah there was some discussion on Zulip about that awhile back
Richard Feldman (Oct 05 2022 at 03:24):I think some form of it will turn out to be a good idea!
Chris Duncan (Oct 09 2022 at 21:27):@JanCVanB: In this topic, they show how to pattern match in the way you were looking for.
Last updated: Jul 26 2025 at 12:14 UTC