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
