Hello, I'm working on a Proto2 Spirit parser. Right now it's really roughed in. There is no AST at the moment. That's TBD; right now I am focused on just getting the build to work. https://gcc.godbolt.org/z/_nBsKi The code is there, but the compiler driving the web site is choking on Spirit. I put the rules in up front; probably ambitious on my part, and am finding an error on: _range %= _int_lit >> -(lit("to") >> (_int_lit | lit("max")); Severity Code Description Project File Line Suppression State Error C1075 '{': no matching token found Kingdom.OrTools.Sat.Params.Generator g:\source\kingdom software\kingdom.ortools\standard\src\kingdom.ortools.sat.params.generator\proto_parser.cpp 205 The Proto2 grammar states: range = intLit [ "to" ( intLit | "max" ) ] I'm considering pairing it back significantly and building the grammar up gradually to make sure it all builds. That's probably a sounder approach anyway. Eventually I want to build up the AST in such a way as to facilitate generating some boilerplate adapter code in my target language (C#). Thoughts? Best regards, Michael Powell https://developers.google.com/protocol-buffers/docs/reference/proto2-spec