Stream: ideas

Topic: no commas needed in multiline collection literals

Richard Feldman (Jun 05 2024 at 23:49):

a note about this:

Richard Feldman said:

actually https://github.com/roc-lang/roc/blob/98df325d76b6b743c6b01f399bbbeaaf0d8108fa/www/wip_new_website/main.roc#L107 is a better example of the downside, would need to have parens across multiple lines if homeLink was moved ahead one spot:

        nav [ariaLabel "primary"], [
            (div [id "top-bar-links"], [
                (a [href "/wip/tutorial"], [text "tutorial"]),
                (a [href "/wip/install"], [text "install"]),
                (a [href "/wip/community"], [text "community"]),
                (a [href "/wip/docs"], [text "docs"]),
                (a [href "/wip/donate"], [text "donate"]),
            ]),
            homeLink,
        ],

so in general DSLs that wanted to use function calls to make the elements would get a lot more parens!

now that we have more whitespace sensitivity because of !, we have an option here that's at least worth discussing: we could make the following Just Work

        nav [ariaLabel "primary"], [
            div [id "top-bar-links"], [
                a [href "/wip/tutorial"], [text "tutorial"]
                a [href "/wip/install"], [text "install"]
                a [href "/wip/community"], [text "community"]
                a [href "/wip/docs"], [text "docs"]
                a [href "/wip/donate"], [text "donate"]
            ]
            homeLink
        ]

Richard Feldman (Jun 05 2024 at 23:50):

the way it would work is that if you go down a line without indenting, that's treated as a standalone list element

Richard Feldman (Jun 05 2024 at 23:51):

so basically instead of trailing commas, you have no commas at the end of lines in a list

Richard Feldman (Jun 05 2024 at 23:51):

(could work the same way for records)

Richard Feldman (Jun 05 2024 at 23:51):

CoffeeScript had something like this as I recall

Richard Feldman (Jun 05 2024 at 23:54):

so this would mean we could do comma-separated function arguments, which has been a consistent recurring request from beginners that seems totally reasonable except for this DSL downside

Agus Zubiaga (Jun 06 2024 at 00:27):

F# lists work like that also. Except it uses semicolons for the single line variant.

Agus Zubiaga (Jun 06 2024 at 00:31):

Overall, I think I prefer the status quo, but I get the consistency argument

Richard Feldman (Jun 06 2024 at 00:39):

yeah I can anticipate beginners being confused by this design too :sweat_smile:

Sky Rose (Jun 07 2024 at 00:17):

what if, the status quo stayed as the correct syntax, but in some cases when it's unambiguous, it still compiled with a warning, and the formatter fixed the commas. If it is ambiguous, it'd be a compile error. That could cut down on chasing syntax errors.

Kevin Gillette (Jun 10 2024 at 14:47):

is [text "..."] a sibling element to a [...] in the above example?

Last updated: Jun 16 2026 at 16:19 UTC