.NET's or JVM's bytecode might be an option. A gazillion of libraries and you don't have to concern yourself with Java's or C#'s obscure grammar corner cases. If you don't like to work on the binary files (and who does) run it through a disassembler first, there are a couple around.
- Small libraries you'd like to see ported to Nim? kobi
- Small libraries you'd like to see ported to Nim? Araq
- Small libraries you'd like to see ported to Nim? Araq
- Small libraries you'd like to see ported to Nim? kobi
- Small libraries you'd like to see ported to Nim... Araq