Category Archives: Tools

Yacc2Latex: Generate a language grammar reference directly form the yacc file

yacc2latex is  available under LGLP licence (dowload here).

As a language designer, I often faced the problem of writing and maintaining a reference (readable) grammar of my language. This is particularly annoying since the reference grammar actually exists as a yacc (or ocamlyacc) file, so why not use a “compiler” that will derived automaticaly the reference grammar from the yacc file ?

Deriving a readable, and reasonably compact, grammar from yacc is not so easy: basically it means discovering the EBNF grammar the designer had in mind when he wrote the yacc.

I found on the internet a nice tool form Kris Van Hees, y2l, but unfortunately relatively old, writen in AWK, and suffering limitations. In particular it was not possible to use it with mly file (ocamlyacc).

I thus decided around 2011 to write my own  yacc to latex “compiler”
for writing the reference manual of “my” languages (Lustre and Lutin).
The tool is is now fairly tested and stable, and I decided to make it available
(through the LGPL licence), hope it may be helpfull for some people !

The main characteristics of yacc2latex are:

  • It integrates a yacc parser, made from scratch,  that is (intended to be) completely agnostic to the embedded programming language , in particular it was made to support mly files (ocamlyacc sources). Indeed, classical C/C++ yacc should also work.
  • It integrates stategies to found EBNF patterns in the yacc (lists, factorization etc.)
  • For advanced use, it provides pragmas to give directives to the translation, in particular a huge grammar can be organized into “sections”.
  • The generated Latex code is parametric: is is possible to change the look of the document by re-defining a set of latex commands.

The distribution  is here: yacc2latex.

As an example of what yacc2latex can do, here  is the reference manual of Lutin, obtained from the ocamlyacc of Lutin.