mirror of
https://git.lyx.org/repos/lyx.git
synced 2024-12-23 13:31:49 +00:00
52 lines
1.6 KiB
Plaintext
52 lines
1.6 KiB
Plaintext
|
Brief discussion on LaTeX grammar
|
||
|
|
---------------------------------
|
||
|
|
|
||
|
|
LaTeX syntax is relatively simple. Any command is like this:
|
||
|
|
|
||
|
|
\command_name [<options>]{<argument_1>}...
|
||
|
|
|
||
|
|
This can be expressed as a grammar in yacc/bison syntax. Capitalized words
|
||
|
|
are tokens (terminals) returned by lex:
|
||
|
|
|
||
|
|
command : LT_command options arguments
|
||
|
|
|
||
|
|
arguments : argument
|
||
|
|
| argument arguments
|
||
|
|
| /* empty: It's possible to not have arguments */
|
||
|
|
;
|
||
|
|
|
||
|
|
argument : '{' anything '}'
|
||
|
|
;
|
||
|
|
|
||
|
|
options : '[' word_list ']'
|
||
|
|
| /* empty: It's possible to don't have options */
|
||
|
|
;
|
||
|
|
|
||
|
|
word_list : LT_word ',' word_list
|
||
|
|
| LT_word
|
||
|
|
;
|
||
|
|
|
||
|
|
anything : /* Any valid token */
|
||
|
|
| command
|
||
|
|
| LT_punctuation
|
||
|
|
| LT_accent
|
||
|
|
| LT_etc
|
||
|
|
;
|
||
|
|
|
||
|
|
This is quite simple and can be easily parsed by any LALR parser as a yacc
|
||
|
|
or bison generated one. BUT the difficulty comes because the number of
|
||
|
|
arguments depends on the value of LT_command, and that the symbols '{' and
|
||
|
|
'}' have more uses that to separate arguments. This expression:
|
||
|
|
|
||
|
|
\section{Hello world} {\bf Once}
|
||
|
|
|
||
|
|
is ambiguos since the parser would interpret the last group as a second
|
||
|
|
argument. Maybe the simpler approach is declaring a grammar for each of the
|
||
|
|
commands that LyX will to understand. Another is that if the parser knows
|
||
|
|
the identity of a command should know also how many arguments should expect.
|
||
|
|
[Aren't these two suggestions almost identical? I mean, if we tell the parser
|
||
|
|
what parameters each command take, we also have a grammar for each of the
|
||
|
|
commands, LyX will understand... Asger]
|
||
|
|
|
||
|
|
AAS
|