Backpack to Work: Towards Backpack in Practice

Edward Z. Yang describes the practical implementation of Backpack, a mixin package system for Haskell that decouples the compiler from the package manager.

Speaker: Edward Z. Yang New York Haskell Meetup(meetup.com/NY-Haskell/events/235377469/) The universal organizing principle for large software systems in programming languages today is the package, the unit by which reusable code may be versioned and distributed. However, most package systems provide only a weak form of modularity, where packages depend directly on other packages. Backpack breaks new ground by arguing mixin packages can be a good fit for package-level modularity. Unfortunately, Backpack as was described in POPL'14 cannot be easily implemented for most existing languages today (including Haskell), because it tightly couples the compiler with the package manager. In this talk, I describe an evolution of the Backpack design which respects the division between package manager and compiler. This is not a paper design: it is principally motivated by our implementation of Backpack in GHC and the Cabal package system, which will be released with GHC 8.2.