Philippe (Mar 21 2022 at 21:32): Philippe (Mar 21 2022 at 21:32):Might sound a bit stupid, but here I go anyway.
Haskell has a dot operator for function composition. Could Roc use it as some sort of pipe?
emptyDict . insert k v
Creates an empty map and then calls insert with the first argument being this empty map.
Derek Gustafson (Mar 21 2022 at 21:34):There is a pipe operator that works exactly that way. It's |>
Philippe (Mar 21 2022 at 21:37):Yes, I know :)
But if people want dot notation, give them dot notation.
After, we can't please everyone. Should we allow code to be written in two different ways or enforce / greatly suggest the Roc way.
Brendan Hansknecht (Mar 21 2022 at 21:41):It would still end up being this in Roc even if we had a . operator for composition:
Dict.empty {} . Dict.insert k v
jan kili (Mar 21 2022 at 21:45):Dots already mean record field access in Roc:
record = { field: "foo", other: "bar" }
transform = \r -> { r & field: "baz" }
a = transform record
b = a.field
c = (transform record).field
d = record |> transform |> .field
b == c == d
It would be very confusing if they also meant composition when followed by a space: record . transform . .field
Richard Feldman (Mar 21 2022 at 22:52):there's actually an FAQ entry on this!
Richard Feldman (Mar 21 2022 at 22:52):not having a pointfree function composition operator is an intentional design decision - more details in the FAQ entry!
Gabriel Pickl (Mar 22 2022 at 18:20):I actually think (.) is one of the best omissions Elm made as a language. The number of times I had to explain to people how it works speaks to it's lack of affordance and readability in my opinion. Elm, and a lot of alternative preludes in Haskell use (<<) (and the imo more reasonable (>>)) instead, because it shows which direction the composition follows. But, to be honest, I rarely reach for point-free style in my programs because pipelines usually read cleaner than function composition
Kevin Gillette (Mar 23 2022 at 02:28):I have found that the clearest way to use point-free function composition, ironically, is to give the resulting function a name, somewhat defeating the point of concise composition.
Last updated: Jul 26 2025 at 12:14 UTC