#include "mcadincl.h"
    
    LRESULT realsumFunction(   LPCOMPLEXSCALAR     c,
                                LPCCOMPLEXSCALAR    a,
                                LPCCOMPLEXSCALAR    b   );

    FUNCTIONINFO    realsum = 
    { 
    "realsum",                          // Name by which mathcad will recognize the function
    "a,b",                              // realsum will be called as realsum(a,b)
    "real sum of scalars a and b",      // description of realsum(a,b)
    (LPCFUNCTION)realsumFunction,       // pointer to the executible code
    COMPLEX_SCALAR,                     // the return type is also a complex scalar
    2,                                  //  the function takes on 2 arguments
    { COMPLEX_SCALAR, COMPLEX_SCALAR}   // both arguments are complex scalars
    };
    
    
    LRESULT realsumFunction(   LPCOMPLEXSCALAR     c,
                                LPCCOMPLEXSCALAR    a,
                                LPCCOMPLEXSCALAR    b   )
    {
        
        // first check to make sure
        // a has no imaginary component
        
        if ( a->imag != 0.0 )   
            return MAKELRESULT(1,1);
          
        if ( b->imag != 0.0 )
            return MAKELRESULT(1,2);        
        
        // otherwise, all is well so add a and b
        c->real = a->real + b->real;
        
        
        return 0;               // return 0 to indicate there was no error
            
    }