we can provide a user definied function which does the same
added: to FunInfo<>:
Stack * stack_tab
size_t stack_index
a stack table and an index to the current stack item
git-svn-id: svn://ttmath.org/publicrep/ezc/trunk@988 e52654a7-88a9-db11-a3e9-0013d4bc506e