On 07/29/2013 01:42 PM, Kinkie wrote: >> After this patch, if I type parametres(foo) instead of parameters(foo), >> will Squid think that I am defining a regular expression instead of >> importing foo where my true regular expressions are stored?
> Guys, one question: I understand that everyone here is very > distrusting of lex/yacc parser generators. I believe your understanding is incorrect. While I would not recommend lex/yacc for Squid, there is no reason to distrust "formal" parsers in general -- they work much better than hand-written ones in most cases. We even wrote a formal parser generator for protocol work some years ago: www.hapy.org. > in cases such as these a full parser would just be able > to make sense from the context, instead of covering corner cases such > as this one. A formal parser needs a good grammar, which Squid configuration currently lacks. While virtually anything can be forced into a formal grammar (albeit not necessarily LALR), doing that for the current Squid configuration file would be rather painful and mostly pointless. For example, while you can force a specific acl type name to be hard-coded into the grammar so that YACC switches to a special part of the grammar tree to parse regular expressions, doing so would defeat the purpose of introducing a formal grammar and formal parsers while _not_ solving the problem of supporting %macros and parameter imports. A big part of the effort related to quoted strings project was to move Squid closer to a good configuration grammar. Doing so is not possible without screwing up some old configurations. Accommodating those is where all the problems and debates start. Once we have a good grammar, we can discuss whether it is a good idea to use a formal parser for it, and which formal parser to use. Cheers, Alex.
