simple_foreign.c

#include <stdio.h>
#include <string.h>
#include <alloca.h>
#include <math.h>

#include "cinterf.h"

/* call as: change_char(+String,+CharPos,+ReplacementString,-ResultString)
   Will take String and replace the character at position CharPos with the
   first character in ReplacementString. Both String and ReplacementString must
   be atoms.
*/
DllExport int call_conv change_char(CTXTdecl)
{
   char *str_in; 
   int  pos;
   char *c, *str_out;

        str_in = (char *) extern_ptoc_string(1);
        str_out = (char *) alloca(strlen(str_in)+1);
        strcpy(str_out, str_in);
        pos = extern_ptoc_int(2);
        c = (char *) extern_ptoc_string(3);
        str_out[pos-1] = c[0];

        /* Now that we have constructed a new symbol, we must ensure that it
           appears in the symbol table.  This can be done using function
           string_find() that searches the symbol table for the symbol, and
           if the symbol does not appear there, it inserts it.  If we are 
           sure that the symbol already appeared in the symbol table there
           is no need to use string_find(). 
         */

        //      extern_ctop_string(4, (char *) string_find(str_out,4));
                extern_ctop_string(CTXTc 4, str_out);

        return TRUE;
}

int my_sqrt(CTXTdecl)
{
   int i = ptoc_int(1);

   extern_ctop_float(2, (float) pow((double)i, 0.5));
   return TRUE;
}

DllExport int call_conv minus_one(CTXTdecl)
{
  int i = extern_ptoc_int(1);
  extern_ctop_int(2,i-1);
  return TRUE;
}

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