writing output files in adequation with a given grammar

[Thomas Lavergne]

Hi all (once again!)
I have Yet Another Question that I prefered to separate in another mail:
What if I want to WRITE grammaticaly correct files. The very basic 
exercise would be to have my program parsing an input file, creates 
objects and rewrite the same input file. Of course, I can do that by 
having 'ObjectPrint()' procedures complying with the given grammar for 
each class. However, if my grammar changes, I need to edit the bison.y 
file AND my objects procedure.
I was just wondering if someone would have a way to re-use a grammar 
bison.y file to deduce correctly formatted outputs?
Thanks