#include "stplugin.h"

// Simple class declaration with a routine to compute varsum, and a routine
// to access the stored sum.
//
class VarLogic {
    public:
        VarLogic(void) { sum = 0.0 ; }  // constructor 
        ~VarLogic(void) { return ; }    // destructor
        ST_retcode computeSum(void) ;   // method defined below 

    protected:
        ST_double sum ;     // object's sum variable
};

// Method to compute our varsum
//
ST_retcode VarLogic::computeSum(void) {
    ST_int      j, k ;
    ST_double   z ;
    ST_retcode  rc ;

    if(SF_nvars() < 2) { 
        return((ST_retcode) 102) ; // not enough variables specified 
    }

    for(j = SF_in1(); j <= SF_in2(); j++) {
        if(SF_ifobs(j)) {
            sum = 0.0 ;
            for(k=1; k < SF_nvars(); k++) {
                if(rc = SF_vdata(k,j,&z)) return(rc) ;  
                sum += z ;
            }
            if(rc = SF_vstore(SF_nvars(), j, sum)) return(rc) ;
        }
    }
    return((ST_retcode) 0) ;
}

// Regular C-style stata_call()
//
STDLL stata_call(int argc, char *argv[]) { 
    VarLogic    vlogic ;        // Object with varsum logic

    return vlogic.computeSum() ;        // Calculate varsum
}