On Thu, Jan 22, 2015 at 10:36 AM, David Topham <dtopham at gmail.com> wrote:
Wonderful! Thank you so much for posting that Phil!
I was not able to build the code using the Makefile because my system does not have libpolyml.so; however, the commands within the Makefile did work, so perhaps that file is not needed? I put them within the attached tgz file in a shell script. Here are the commands in that file:
gcc -fPIC -g -Wall -c testlib.c -o testlib.o gcc -shared -Wl,-soname,testlib.so.1 -o testlib.so.1 testlib.o polyc call_c_test_10.sml LD_LIBRARY_PATH=. ./a.out
and this runs successfully displaying the output in an X Window!
I think this is a viable approach to integrating PolyML with a GUI or at least graphics output but of course will require lots of experimenting...I wish I had tons of time, but will only be able to try things once-in-a-while now that a new semester has begun.
Here is the modified C program that invokes the Motif window: (but it is also in the attached tgz file if you want to try it)
#include <stdio.h> #include <Xm/Xm.h> #include <Xm/Label.h> #include <stdlib.h>
double (*sml_hypot) (double x, double y);
void c_main (void) { double a, b, c;
a = 3.0; b = 4.0; printf("a = %.6f\n", a); printf("b = %.6f\n", b);
c = sml_hypot (a, b); /* call back to SML! */
printf("c = %.6f\n", c); fflush(stdout);
char msg[256]; sprintf(msg,"c = %.6f\n", c); Widget shell; XtAppContext app; XmString xmstr; int argc = 1; char* argv[] = {"polygui" }; shell = XtAppInitialize ( &app, "Memo", NULL, 0, &argc, argv, NULL, NULL, 0 ); xmstr = XmStringCreateLtoR ( msg, XmFONTLIST_DEFAULT_TAG ); XtVaCreateManagedWidget ( "message", xmLabelWidgetClass, shell, XmNlabelString, xmstr, NULL ); XmStringFree ( xmstr ); XtRealizeWidget ( shell ); XtAppMainLoop ( app );return; }
On Thu, Jan 22, 2015 at 4:00 AM, <polyml-request at inf.ed.ac.uk> wrote:
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Today's Topics:
- Re: linking polyML modules to C (Phil Clayton)
Message: 1 Date: Wed, 21 Jan 2015 20:20:06 +0000 From: Phil Clayton <phil.clayton at veonix.com> To: polyml at inf.ed.ac.uk Subject: Re: [polyml] linking polyML modules to C Message-ID: <54C009F6.1050209 at veonix.com> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
19/01/15 12:19, David Matthews wrote:
On 19/01/2015 04:34, David Topham wrote:
Thanks David for your response.
While searching I found this comment you made earlier:
"The foreign-function interface allows for call-back functions so there is the mechanism to produce a C function that when called calls an ML function."
in
http://stackoverflow.com/questions/17580386/shared-libraries-in-poly-ml
Doesn't this indicate a mechanism that allows an SML function to be called from C?
Yes, but the "main program" still has to be in ML. You can call C library functions and pass an ML function as an argument.
Or the ML functions can be passed via global variables that are initialized from the ML side - see attached example. That may be easier if there are a large number of ML functions.
Actually, I did wonder whether this could be used as a way of exporting ML functions to create a library that could be called from a C main program and came to the conclusion that it was going to be too complicated. Poly/ML uses libffi to interface with C. libffi can build closures that wrap around ML functions so that these can be passed into C. The format of the closure it constructs differs markedly depending on the particular architecture since different architectures have different calling conventions for C. The closure is a data structure with pointers in it. Exporting it would require turning the pointers into relocations that the linker/loader will understand. libffi simply doesn't provide that information. It's there by implication in the source code but not explicitly.
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