Question

How should I name my Haskell modules for a program, not a library, and organize them in a hierarchy?

I’m making a ray tracer called Luminosity. First I had these modules:

Vector Colour Intersect Trace Render Parse Export

Each module was fine on it’s own, but I felt like this lacked organization.

First, I put every module under Luminosity, so for example Vector was now Luminosity.Vector (I assume this is standard for a haskell program?).

Then I thought: Vector and Colour are independent and could be reused, so they should be separated. But they’re way too small to turn into libraries.

Where should they go? There is already (on hackage) a Data.Vector and Data.Colour, so should I put them there? Or will that cause confusion (even if I import them grouped with my other local imports)? If not there, should it be Luminosity.Data.Vector or Data.Luminosity.Vector? I’m pretty sure I’ve seen both used, although maybe I just happened to look at a project using a nonconventional structure.

I also have a simple TGA image exporter (Export) which can be independent from Luminosity. It appears the correct location would be Codec.Image.TGA, but again, should Luminosity be in there somewhere and if so, where?

It would be nice if Structure of a Haskell project or some other wiki explained this.

Answer 1

First of all I put every module under Luminosity

I think this was a good move. It clarifies to anyone that is reading the code that these modules were made specifically for the Luminosity project.

If you write a module with the intent of simulating or improving upon an existing library, or of filling a gap where you believe a particular generic library is missing, then in that rare case, drop the prefix and name it generically. For an example of this, see how the pipes package exports Control.Monad.Trans.Free, because the author was, for whatever reason, not satisfied with existing implementations of Free monads.

Then I thought, Vector and Colour are pretty much independent and could be reused, so they should be separated. But they’re way to small to separate off into a library (125 and 42 lines respectively). Where should they go?

If you don’t make a separate library, then probably leave them at Luminosity.Vector and Luminosity.Colour. If you do make separate libraries, then try emailing the target audience of those libraries and see how other people think these libraries should be named and categorized. Whether or not you split these out into separate libraries is entirely up to you and how much benefit you think these separate libraries might provide for other people.