adding variable to yyparse function scope

[Bob Rossi]

Hi,

Can I add a variable to the yyparse function scope from within my parser
some how? I want to ensure that the parser is reentrant. I only
currently see how to add variables to the top of the file with the 
prologue rule:
  http://www.gnu.org/software/bison/manual/html_mono/bison.html#Prologue
and to the end of the file with the epilogue rule:
  http://www.gnu.org/software/bison/manual/html_mono/bison.html#Epilogue

Any ideas?

Thanks,
Bob Rossi