This chapter gives an overview of Semantic and its goals.
Ordinarily, Emacs uses regular expressions (and syntax tables) to analyze source code for purposes such as syntax highlighting. This approach, though simple and efficient, has its limitations: roughly speaking, it only “guesses” the meaning of each piece of source code in the context of the programming language, instead of rigorously “understanding” it.
Semantic provides a new infrastructure to analyze source code using
parsers instead of regular expressions. It contains two
built-in parser generators (an LL generator named
Bovine and an LALR generator named Wisent,
both written in Emacs Lisp), and parsers for several common
programming languages. It can also make use of external
parsers—programs such as GNU Global and GNU IDUtils.
Semantic provides a uniform, language-independent API for accessing the parser output. This output can be used by other Emacs Lisp programs to implement “syntax-aware” behavior. Semantic itself includes several such utilities, including user-level Emacs commands for navigating, searching, and completing source code.
The following diagram illustrates the structure of the Semantic package:
The words in all-capital are those that Semantic itself provides. Others are current or future languages or applications that are not distributed along with Semantic.
Applications
and
Utilities
-------
/ \
+---------------+ +--------+ +--------+
C --->| C PARSER |--->| | | |
+---------------+ | | | |
+---------------+ | COMMON | | COMMON |<--- SPEEDBAR
Java --->| JAVA PARSER |--->| PARSE | | |
+---------------+ | TREE | | PARSE |<--- SEMANTICDB
+---------------+ | FORMAT | | API |
Scheme --->| SCHEME PARSER |--->| | | |<--- ecb
+---------------+ | | | |
+---------------+ | | | |
Texinfo --->| TEXI. PARSER |--->| | | |
+---------------+ | | | |
... ... ... ...
+---------------+ | | | |
Lang. Y --->| Y Parser |--->| | | |<--- app. ?
+---------------+ | | | |
+---------------+ | | | |<--- app. ?
Lang. Z --->| Z Parser |--->| | | |
+---------------+ +--------+ +--------+