Path: utzoo!utgpu!watserv1!watmath!att!rutgers!cs.utexas.edu!rice!uupsi!kepler1!fcaggian
From: fcaggian@kepler.com (Frank Caggiano)
Newsgroups: comp.lang.eiffel
Subject: eiffel and external c routines
Message-ID: <444@kepler1.kepler.com>
Date: 18 Oct 90 03:09:45 GMT
Organization: Kepler Financial Mgmt., Setuket, NY
Lines: 75

I have been trying to access an Eiffel object from a C routine
and am having no luck.  What I need to do is access a fixed list
of intergers from the C routine.  I have tried all the ways I
can think of using the routines shown on pages 220-221
of Eiffel the language.  They don't specifically show
the object being passed in however so is this possible?

Also while I've ben going through this I thought that if I 
created the object in C passed it back to eiffel and then passed
it back to C maybe it would work then. GHowever when I went to write
the C call to eif_create I bummped up afgainst the fact that 
FIXD_LIST is a constrained type.  How do you create a constrained
type in C ?  All I could comme up with was:

	eif_create("fixed_list[integer]",some-number)
but seems a bit far fechted. I haven't had time to try it out.
Anyone have any ideas?

Below is an example of code for my first problem:

The Eiffel part:
class CEIF 

feature

	Create is
		external
			foo: language "C"
		local
			x: FIXED_LIST[INTEGER]
		do
			x.Create(3);
			x.put_i_th(1,1);
			x.put_i_th(2,2);
			x.put_i_th(3,3);
			x.start;
			io.putint(x.item); io.new_line; 
			x.forth;
			io.putint(x.item); io.new_line; 			
			x.forth;
			io.putint(x.item); io.new_line; 			
			x.start;
			foo(x);
		end;
end;


The C part:
#include "/usr/local/Eiffel/files/_eiffel.h"
foo(x)
    OBJPTR x;
{

    int i;
    extern int eif_err;

    for (i = 1; i <= 3; i++) {
	printf("i = %d (%d) {%d} [%d]\n",i,eif_err,eif_attr(x,"count"),
	       eif_attr(x, "item"));
	eif_rout(x,"forth");
    }
}

what prints out (from the C part):
i = 1 (-1) [0] [0]
i = 2 (-1) [0] [0]
i = 3 (-1) [0] [0]

The printout in Eiffel is ok.

-- 
Frank Caggiano                      INTERNET: fcaggian@kepler.com  
Kepler Financial Management, Ltd.       UUCP: ..!uunet!kepler1!fcaggian
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