Generics Proposal for 202Y video call

Announcements
7

Thank you everybody who attended, we had I believe 10 participants. Here is a summary:

  • The above 3 areas are good, the last bullet point should be generalized to other corner cases and “warts” in Fortran, although the rank agnostic arrays is definitely one of the main ones

  • We should prototype the Fortran pseudocode for the second bullet point above using the abstract class in Fortran and we need to answer exactly how the templates+concepts differ from the abstract class: templates are strictly compile time and allow an effective multiple inheritance.

  • For the second bullet point should be extended with multiple templates / constraints to see how it looks like

  • @everythingfunctional will contribute a Haskell example of strong concepts for the second bullet point

  • We need to figure out how parametrized modules Fortran proposal fits into this, whether it is one possible implementation of the “strong concept” idea, or something else.

  • We should find a better terminology for templates + strong concepts. Such as type parameters and constraints/traits.

  • Rust requires to explicitly specify that a user type is satisfying a trait, Go does not. We seemed to agree we should go the Go route, which seems to be natural for users. The reason Rust does it is so that you can append more methods to a class outside where it is defined, but in Fortran (as in Go I believe), you define everything at one place, so it seems more natural to satisfy the traint/concept/constraint implicitly.

  • We should make progress on the above 3 areas as much as we can. As we make further progress, the effort will serve as a “prototype” that allows people to have a concrete idea about how the generics could be done and allows them to reason about the various proposal. From there we need to then write down use cases and requirements for generics. And then there will be multiple proposals how they could be implemented, using the ideas from our “prototype” (or other ideas).

  • As we make progress, we need to think how to get the whole J3 committee up to speed with the “strong concept” and other ideas, and convince them this is a good “requirement” that the compiler checks both the library code and a user code. And other ideas that we figure out in the Generics subgroup.

  • We will meet every other week for 1h.

If I missed anything, please let me know.

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