The future of Emacs, Guile, and Emacs Lisp

Posted Oct 15, 2014 16:58 UTC (Wed) by nix (subscriber, #2304)
In reply to: The future of Emacs, Guile, and Emacs Lisp by Cyberax
Parent article: The future of Emacs, Guile, and Emacs Lisp

Yeah. Emacs has supported this for *years* via CEDET and the semantic bovinator. It's still slow, but for C, C++, and Lisp it is perfectly usable (other languages suffer from a lack of grammars).

The future of Emacs, Guile, and Emacs Lisp

Posted Oct 15, 2014 18:04 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link] (4 responses)

CEDET is nice, but it fails to deliver.

It's mostly used for simple completions and nothing else. IntelliJ products can use their semantic model for smart code refactoring and inspection.

Oh, and CEDET's parser is pitifully inadequate even for plain C, it has no hope of ever understanding C++ completely.

The future of Emacs, Guile, and Emacs Lisp

Posted Oct 21, 2014 16:30 UTC (Tue) by nix (subscriber, #2304) [Link] (3 responses)

It's sufficient for what I want to do with it for C.

Obviously getting it right for C++ is impossible -- but you need a C++ compiler to understand C++ properly. Actually you need something *better*, because you want to be able to parse incomplete, partially written, and syntactically invalid code as much as possible. That sort of error recovery is *hard*.

The future of Emacs, Guile, and Emacs Lisp

Posted Oct 21, 2014 16:36 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link] (2 responses)

Clang mostly gets error recovery right. Aside from them, people at IntelliJ are working on Nitra ( https://github.com/JetBrains/Nitra ) are trying to make it easier for complicated languages and they are tackling C++ now.

Pure C is also not that easy, because lots of C++'s syntactic ambiguity actually comes from C.

The future of Emacs, Guile, and Emacs Lisp

Posted Oct 23, 2014 1:34 UTC (Thu) by cmccabe (guest, #60281) [Link] (1 responses)

C is "very close to having a context-free grammar."
Details here: http://eli.thegreenplace.net/2007/11/24/the-context-sensi...

C++ has an undecidable grammar.

I can parse C with yacc. I could never hope to parse C++ with anything but a hand-written parser.

The future of Emacs, Guile, and Emacs Lisp

Posted Oct 23, 2014 11:41 UTC (Thu) by jwakely (subscriber, #60262) [Link]

Yeah, C doesn't have to parse anything remotely like:

int Foo (int i = T<1, int>::i);

(See http://open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#325 for other examples like that)