H2JVM - A Haskell Library for writing JVM Bytecode

That’s fair, for appending single instructions it’s probably worse, although I haven’t benchmarked. I think it should be better when you can append chunks of several instructions, so that it works like a builder.

The more important thing imo is to avoid the possibility of a “sign error” by putting <> in a natural order, and reverse-list also helps with that.