Kilian Vounckx (May 14 2023 at 21:00): Kilian Vounckx (May 14 2023 at 21:00):Not sure if this is the right stream for this, but I wanted to check here before raising an issue.
I was playing around with roc and I think I found a bug. A minimal reproduction can be done in the repl:
Bool.false && Bool.false || Bool.true && Bool.true
This should give Bool.true as a result (simplifies to Bool.false || Bool.true), but it gives Bool.false.
Is this a known issue? I am using a compiler built from source yesterday
Kilian Vounckx (May 14 2023 at 21:01):Adding parenthesis around the two '&&' comparisons makes it work, which makes me think it is an issue with the order of operations
Brendan Hansknecht (May 14 2023 at 21:01):Does || run before &&....is that correct? Don't recall normal ordering rules.
Brendan Hansknecht (May 14 2023 at 21:02):Simplify to Bool.false && Bool.true && Bool.true
Kilian Vounckx (May 14 2023 at 21:05):In every programming language I know of && runs before ||
Kilian Vounckx (May 14 2023 at 21:05):In electronics and mathematics the and operator also has precedence
Brendan Hansknecht (May 14 2023 at 21:06):Not python (assuming i just typed this in correctly) nvm...typed it wrong
Kilian Vounckx (May 14 2023 at 21:07):False and False or True and True
This in a python repl gives True
Brendan Hansknecht (May 14 2023 at 21:12):It is a super easy fix, looks like we have a precedence table and they are equal precedence currently.
Brendan Hansknecht (May 14 2023 at 21:13): Brendan Hansknecht (May 14 2023 at 21:14):Just incrementing all precedence by 1 except for OR is a fix.
Brendan Hansknecht (May 14 2023 at 21:14):Then and has a precendence 1 higher. Not sure if we picked equal precedence for a specific reason.
Brendan Hansknecht (May 14 2023 at 21:15):I always use parens in cases like these
Brendan Hansknecht (May 14 2023 at 21:20):Because they are equal precedence, this is current behaviour:
Bool.false && Bool.false || Bool.true && Bool.true
# is running as:
Bool.false && (Bool.false || (Bool.true && Bool.true))
Oh I see
I think it is best to have either && be higher precedence, or have the compiler enforce you to put parens
Brendan Hansknecht (May 14 2023 at 21:22):Probably. No idea why it is this way, just digging into the compiler and noting how it currently is.
Kilian Vounckx (May 14 2023 at 21:23):Should I raise an issue for it?
Kilian Vounckx (May 14 2023 at 21:23):I could probably fix it myself, but it would be tomorrow (in my timezone it is almost midnight)
Brendan Hansknecht (May 14 2023 at 21:24):That is probably reasonable. Though should wait for a comment from someone else before fixing. It may be working as intended. I don't know the background here. But yeah, fix is super simple, I already have one.
Martin Stewart (May 14 2023 at 21:25):I'd like to second the idea of the compiler forcing you to place parens when && and || are used. I can never keep straight which takes precedence (unlike +, -, *, /, ^). That said, fixing the precedence seems fine otherwise.
Kilian Vounckx (May 14 2023 at 21:28): Kilian Vounckx (May 14 2023 at 21:30):Martin Stewart said:
I'd like to second the idea of the compiler forcing you to place parens when && and || are used. I can never keep straight which takes precedence (unlike +, -, *, /, ^). That said, fixing the precedence seems fine otherwise.
I'm from an electrical engineering background where these operators are used a lot. In my case I never confuse them, which is why I found the output in roc odd. So my preference is having the correct precedence.
Also fine with the enforced parenthesis though
Martin Stewart (May 14 2023 at 21:31):I guess it depends how many other people find it difficult to remember boolean operator precedence.
Brendan Hansknecht (May 14 2023 at 21:37):@Richard Feldman or @Folkert de Vries any history on this ordering? Is it a bug or is it intentional for some specific reason?
Georges Boris (May 14 2023 at 21:50):I'm +1 for compiler warning here - seems similar to confusing infix functions in a pipeline like |> ((/) 2 (elm)
I can understand it might be obvious if the person knows the caveat but imo Roc is trying to push for making things safe even for beginners so a compiler warning for error-prone assignments seems the right choice
Richard Feldman (May 14 2023 at 22:05):I'm pretty sure I just started with whatever Elm did on that
Richard Feldman (May 14 2023 at 22:06):I like the idea of forcing parens there :thumbs_up:
Ajai Nelson (May 14 2023 at 22:10):It looks like Elm returns true:
> False && False || True && True
True : Bool
Cool. So then two issues. 1 fix the precedence to match elm and most programming languages again
Brendan Hansknecht (May 14 2023 at 22:17):2 force parens
Richard Feldman (May 14 2023 at 23:12):I think if we force parens the precedence becomes moot, no?
Brendan Hansknecht (May 14 2023 at 23:16):Oh, i was thinking warning if no parens, so precedence still matters. For example in repl or dev
Brendan Hansknecht (May 14 2023 at 23:16):If we make parens 100% required than it is moot
Richard Feldman (May 14 2023 at 23:27):ah fair
Richard Feldman (May 14 2023 at 23:27):good idea about making it a warning :thumbs_up:
Richard Feldman (May 14 2023 at 23:27):in that case, yeah might as well change the precedence too
Agus Zubiaga (May 14 2023 at 23:43):Do warnings make sense for Roc when roc run runs your program even with compiler errors?
Richard Feldman (May 14 2023 at 23:51):yeah, the distinction is:
crash, so your program may crash if you run it anyway"crash, but you should really fix it; it will cause the process to exit with a nonzero exit code, and therefore fail CI" (and alaso if you're a package, this will block being able to publish on the official registry)roc dev will run as soon as there are no errors, even if there are still warnings Agus Zubiaga (May 14 2023 at 23:52):Ah, the nonzero exit code is key. Without that I'd be worried it would result in the usual pile of ignored warnings.
Richard Feldman (May 14 2023 at 23:53):yeah my experience on warnings is that if it's hard to ignore them from day 1, they'll never pile up
Richard Feldman (May 14 2023 at 23:53):but of course they still shouldn't block running your program if you don't want to deal with them right away (and neither should errors!)
Agus Zubiaga (May 14 2023 at 23:54):Yeah, that's a good balance :)
Anton (May 15 2023 at 08:33):This kind of warning seems to be most suited for the formatter.
Brendan Hansknecht (May 15 2023 at 14:16):So no warning when doing roc run/dev/build? Only a warning on roc format?
Brendan Hansknecht (May 15 2023 at 14:17):I would be concerned that roc format won't be in the hot loop enough to get cared about, even if it gives a warning. So I guess this depends on if we think that in general this should be fixed or if we don't care too much. Personally, I always add the parens in these kinds of cases, so I am totaly happy with the compiler warning and this being enforced in general. I think using them directly is simply more error prone and harder to read.
Anton (May 15 2023 at 14:21):So no warning when doing
roc run/dev/build? Only a warning onroc format?
Yes, that's what I was thinking
I think using them directly is simply more error prone and harder to read.
I agree, but this seems the case for a lot of things that are currently fixed by the formatter :p
Brendan Hansknecht (May 15 2023 at 14:24):Would the formatter give a warning, or just fix it by adding in the parens as roc sees it?
Brendan Hansknecht (May 15 2023 at 14:24):Cause that is what actually would get parsed?
Agus Zubiaga (May 15 2023 at 14:37):Automatically adding parens sounds dangerous because it might happen somewhere you're not currently looking at and you might not notice the warning which won't appear in subsequent runs.
Anton (May 15 2023 at 14:39):I first thought that the formatter should add parens as roc sees the order but then it might be easy to miss that the order is not how you want it. So maybe a compiler warning is more appropriate
Agus Zubiaga (May 15 2023 at 14:40):Yeah, that's what I think as well. Also, I'm not sureroc format warnings should be a thing as users will likely run it automatically on save and they'll probably miss them. At least that's what (almost) everybody does in Elm.
Kilian Vounckx (May 15 2023 at 16:34):If there are going to be compiler warnings for these operators, should there be a discussion for others as well (comparison operators vs equality operators,...)?
Richard Feldman (May 15 2023 at 17:08):yeah totally, and personally I've thought for years that we should do warnings like this for arithmetic operators
Richard Feldman (May 15 2023 at 17:08):e.g. 1 + 2 * 3 - 4 should be explicitly rewritten to 1 + (2 * 3) - 4
Last updated: Jul 26 2025 at 12:14 UTC