[PPL-devel] Bignums and the foreign language interface

[Roberto Bagnara]

Hi there,

how can bignums be communicated to/from Ciao Prolog?
More precisely, since we have

$ ciao
Ciao-Prolog 1.9 #34: Sat Nov 30 19:17:43 CET 2002
?- current_prolog_flag(bounded, X).

X = false ?

yes
?-

integers are unbounded.  However, the function

   ciao_term ciao_integer(int i)

allows to build only integers that fit in a machine
word.  The problem with the design of the function

   int ciao_to_integer(ciao_term term)

appears to be more serious, as the C application seems
to have no way of detecting whether the conversion was
successful or not.
It would seem better to define something like

   int ciao_to_integer(ciao_term term, long* pl)

so that 0 is returned if the conversion failed (in which
case *pl has not been touched), and a number different from 0
otherwise.  Bignums could then be communicated with a pair
of functions ciao_get_number_chars() and ciao_put_number_chars().
What do you think?
Best wishes to you all

      Roberto

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it