In addition to what Matthias says, you can also sometimes break these kinds of cycles using lazy-require, which defers the requiring the other module until it is first needed. This is simpler than using units and provides stronger guarantees than using callbacks, but it is a bit more ad-hoc than both of them, and it only works when the lazily-loaded module isn’t needed as part of module initialization (that is, the function isn’t called from the top level of a module). When it works, though, it can be a less invasive solution to the problem.
Alexis > On May 14, 2018, at 4:28 PM, David Storrs <[email protected]> wrote: > > My application retrieves chunks of files from the network and writes > them to disk, as well as writing certain data about them to the > database (e.g. where they are on disk and where they came from on the > network). > > I've split these functions into separate files: > > app/network/chunks.rkt > app/lib/db/chunks.rkt > > This worked fine until now, but I've gotten to a point where they're > circular -- the network code needs to receive the chunk and then > forward it to the DB code, but if certain error conditions come up > then the DB code needs to tell the network code to re-request the > data. > > There's various ways I could work around this (simplest being to put > all the functions in one file), but I'm wondering if there's a > recommended way? C would solve this with a .h file. Perl would solve > it with function prototypes (or simply be able to sort it out without > intervention). What is the preferred Racket way, or am I simply not > thinking about it correctly? -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
