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