...
double vet[] = { _a, _b, _c, _d, _e, _f };
double 	r = min(_a, _b);
r= min(r,_c); 
r= min(r,_d);
r= min(r,_e);
r= min(r,_f);

return r; 

double vet[] = { _a, _b, _c, _d, _e, _f };
double min = vet[0];
for (int i=0; i<(sizeof vet/sizeof *vet ); i++)
{
     if(vet[i] < min){ min = vet[i];}
}
return min;