On 04.02.12 16:25, Michael Haberler wrote: > This is different from the original language: the pre-oword syntax was > context-free, which is why there's a meaningful EBNF in the Tom Kramer > report, and working context-free parsers based on ANTLR and bison like > here: http://fennetic.net/irc/emc3/src/emc/interpreter/)
It is worth noting here that the link points to another grammar which is empty of working gcodes. Look in: http://fennetic.net/irc/emc3/src/emc/interpreter/rs274ngc-flex-bison/parser.ypp Below the top-level block structure, we see grammar for only expressions and parameter settings. Like the empty grammar posted upthread, it is devoid of any grammar for gcodes. After checking both parser.ypp and the lexer (scanner.l) several times, I find that the letter 'G' is passed through, like a dose of epsom salts, without touching the sides. The so-called parser does not even know that a gcode exists. It looks like an "Alphabet parser with some expressions." The empty grammars(*1) put up so far look disappointingly like that first 2% of a grammar that a uni student has to whack together in order to pass computer science 101. All the hard work remains to be done. I wonder if there is one out there with any gcodes in it? On 04.02.12 16:25, Kenneth Lerman wrote: > The use of matching labels to resolve ambiguity was just a cheap trick > to lower the cost of implementation. There is no reason that we should > keep the labels on control structures. We should then follow the same > rules that C uses. +1 Erik (*1) Empty of any handling of the input. There's not even a yyerror() function to generate syntax error messages. Since a yacc/bison parser calls that function on any syntax error, it's hard to see how these toys can be called a "working grammar". -- The Roman Rule The one who says it cannot be done should never interrupt the one who is doing it. ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
