/**********************************************
* C calls a Perl subroutine and pushes two 
* double scalars.These two scalars are modified 
* in the sub and popped.
* 7.2.2014 Frank
**********************************************/
#include <EXTERN.h>
#include <perl.h>
#include <stdio.h>

/*---------------------------------------------
* global variables
*--------------------------------------------*/
double x, y;
int    icoun;
static PerlInterpreter *my_perl; 

/*---------------------------------------------
* the C-"Assembly"routine
*--------------------------------------------*/
static void harry(double x, double y)
{
printf("in Harry vor call, x= %lf, y= %lf\n",x,y);

dSP;     
ENTER;
SAVETMPS;

PUSHMARK(SP);  

XPUSHs(sv_2mortal(newSVnv(x))); // PUSH one double "n"
XPUSHs(sv_2mortal(newSVnv(y))); // PUSH one double "n"

PUTBACK;

icoun= call_pv("points",G_ARRAY);

SPAGAIN;

y= POPn;  // POP one double "n"
x= POPn;  // POP one double "n"

printf("in Harry after call, icoun= %d, x= %lf, y= %lf\n",icoun,x,y);

PUTBACK;
FREETMPS;

LEAVE;
}

/*---------------------------------------------
* main
*--------------------------------------------*/
int main(int argc, char **argv, char **env)
{
char *my_argv[]= {"", "punkte2.pl"};

x= 3.1416;
y= 47.11;

printf("Controll of the entry values\n");
printf("X= %lf, Y= %lf\n",x,y);

/*=============================================
* start Perl Interpreter
*============================================*/
my_perl= perl_alloc();
perl_construct(my_perl);

perl_parse(my_perl,NULL, 2, my_argv, (char **)NULL);
perl_run(my_perl);

/*=============================================
* launch the C-"Assembly" routine
*============================================*/
harry(x,y);

/*=============================================
* ...and clean up
*============================================*/
perl_destruct(my_perl);
perl_free(my_perl);
}


#*********************************************
# the Subroutine points
# 7.2.2014 Frank
#*********************************************
sub points
{
my ($xup,$yup)= @_;  # value,value

print "in der Subroutine\n"; # kleiner Test

print "XUP= $xup, YUP= $yup\n";

$xup *= 3;
$yup *= 4;

return $xup, $yup;
}