Stream: beginners

Topic: syntax question: @ :=

roovo (Dec 15 2022 at 12:25):

Hi - I'm looking at the Parser/Core.roc source in roc examples and see the following:

Parser input a := input -> ParseResult input a

buildPrimitiveParser : (input -> ParseResult input a) -> Parser input a
buildPrimitiveParser = \fun ->
    @Parser fun

am confused as to what is the significance/meaning of the := in the definition of Parser as well as the @ in the body of the buildPrimativeParser function. I can't find either mentioned in the tutorial or any other doc, so if it is explained somewhere that would be great to know too. Thanks

Erik (Dec 15 2022 at 14:34):

Ahh I believe that is the opaque type syntax. There is some info in this doc -> https://github.com/roc-lang/roc/blob/main/roc-for-elm-programmers.md#opaque-types

roovo (Dec 15 2022 at 14:55):

Fantastic - thank you :)

Erik (Dec 15 2022 at 14:59):

no problem! :)

Last updated: Jul 26 2025 at 12:14 UTC