Contents - Index


Example .DLF External Function in C++

 

The following source code creates a .DLF external function that returns the sum of two numbers.  The function is accessed from EES with a statement of the following format;  This function does not provide input or output units so there will be no unit checking when this function is called.

 

s=SUM_C(x,y)

 

_________________________________________________________

 

#include <windows.h>

 

 

// Structure for handling ees calling syntax

struct EesParamRec {

  double value;

  struct EesParamRec *next;

};

 

 

// Tell C++ to use the "C" style calling conventions rather than the C++ mangled names

  extern "C"  {

 

__declspec (dllexport) double SUM_C(char s[256], int& mode, struct EesParamRec *input_rec)

{

double In1, In2, sum_res;

int NInputs;

 

if (mode==-1) {  

  strcpy(s,"a = SUM_C(b,c)"); // return example call string

  return 0;

}

 

// Check the number of inputs

    NInputs=0;

    EesParamRec * aninput_rec=input_rec;

while (aninput_rec!= 0)

{

  aninput_rec= aninput_rec->next;

  NInputs++;

};

if (NInputs!=2) {

  strcpy(s,"SUM_C expects two inputs");

  return 0;

}

 

In1= input_rec->value;

input_rec=input_rec->next;

In2=input_rec->value;

sum_res = In1+In2;

 

return sum_res;

}

 

};

 

 

This procedure was compiled into file SUM_C.DLF using the Microsoft Visual Studio.