I hadn't followed the link in article originally to get to https://mobile.twitter.com/RonAvitzur/status/146102321572409.... So literally the process of parsing the expression and producing the byte code is the performance challenge now? Or is it also walking the bytecode to do anything?
My basic question would be: why not go back to flex/bison/yacc/whatever via C-FFI? (But I think it would still be bad, since you'll want to get to a Swift data structure for your ops and those will still have the Arc issues)