I'm working on a mod that adds compressed blocks and I would like to add compatibility for ex compressum. So I was looking around your source code and I can't seem to find a way to add recipes to the compressed hammer/sieve from an external mod.
If there isn't currently a way to add recipes, could you add that? (unless you're no longer updating the 1.7.10 branch)

The 1.7.10 branch is indeed no longer receiving new features, and it didn't have a public API (and the code wasn't the nicest as I followed Ex Nihilo's lead). A quick look suggests adding support will be a pain as you'd have to use Reflection to access the private methods. I'll add an API on the 1.11 version for the future.

#156

So it turns out I didn't have to use reflection, here's what I did for anyone who wants to know.

CompressedHammerRegistry.getSmashables().put(new ItemAndMetadata(Blocks.grass, 0), new Smashable(Blocks.grass, 0, Items.apple, 0, 1.5F, 4.2F));

HeavySieveRegistry.getSiftables().put(new ItemAndMetadata(Blocks.grass, 0), new SiftingResult(Items.apple, 0, 0.4F));

These are of course just example recipes.