[Ecls-list] ecl_def_c_function with a non-void function

Erik Winkels aerique at xs4all.nl
Mon Apr 12 12:45:50 UTC 2010


I seem to be on my biannual ECL exploration.

(Also see the code listing at the bottom of this e-mail.)

I'm playing around with ecl_def_c_function and this works:

    ecl_def_c_function(ecl_read_from_cstring("test-void"), &test_void, 0);

If I do "(test-void)" from the ECL repl I get the expected ":TEST-VOID"

However, this gives compilation errors for me:

    ecl_def_c_function(ecl_read_from_cstring("test-2args"), &test_2args, 2);


    $ g++ -lecl -otest test.cpp 
    test.cpp: In function 'int main(int, char**)':
    test.cpp:28: error: invalid conversion from 'cl_lispunion* (*)(cl_lispunion*, cl_lispunion*)' to 'cl_lispunion* (*)()'
    test.cpp:28: error:   initializing argument 2 of 'void ecl_def_c_function(cl_lispunion*, cl_lispunion* (*)(), int)'

I can understand why but I haven't been able to write the correct
ecl_def_c_function to make this work.  I've tried some approaches myself and
I've tried thing I found by Googling but those seem to have been written
for an older ECL version.


// test.cpp
// compiling: g++ -lecl -otest test.cpp
// o http://www.den.rcast.u-tokyo.ac.jp/~salvi/archive/snippets/ecl-test.html
// o http://code.google.com/p/m-nebula/source/browse/#svn/trunk/code/src/ecl

#include <iostream>
#include "ecl/ecl.h"

// Prototypes

cl_object test_void ();
cl_object test_2args (cl_object, cl_object);

// Functions

int main (int argc, char* args[])
    cl_boot(argc, args);

    // We are computing unnormalized numbers at some point.
    //si_trap_fpe(Ct, Cnil);

    ecl_def_c_function(ecl_read_from_cstring("test-void"), &test_void, 0);
    ecl_def_c_function(ecl_read_from_cstring("test-2args"), &test_2args, 2);

    cl_object obj = ecl_read_from_cstring("si:top-level");
    cl_funcall(1, obj);

    return 0;

cl_object test_2args (cl_object first, cl_object second)
    std::cout << "first: " << type_of(first) << ", second: " << type_of(second)
              << std::endl;
    return ecl_read_from_cstring(":test-2args");

cl_object test_void ()
    return ecl_read_from_cstring(":test-void");

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