Question

I frequently encounter situations, especially with sorting in C++, where I am comparing a series of fields in order to compare a larger structure. A simplified example:

struct Car{     Manufacturer make;     ModelName model;     Year year; };  bool carLessThanComparator( const Car & car1, const Car & car2 ){     if( car1.make < car2.make ){         return true;     }else if( car1.make == car2.make ){         if( car1.model < car2.model ){             return true;         }else if( car1.model == car2.model ){             if( car1.year < car2.year ){                 return true;             }         }     }      return false; } 

My instinctive approach seems cumbersome, especially for more than 3 fields. How would you structure this series of comparisons in C++? Do other languages provide a more succinct or elegant syntax?

Answer 1

Well, if your function hits a return in the if clause, there’s no need for an explicit else, since it would have already bailed out. That can save on the ‘indent valley’:

bool carLessThanComparator( const Car & car1, const Car & car2 ) {     if( car1.make < car2.make )         return true;      if ( car1.make != car2.make )         return false;      if( car1.model < car2.model )         return true;      if( car1.model != car2.model )         return false;      if( car1.year < car2.year )         return true;      return false; } 

I like MarkusQ’s LISPish short-circuiting approach as well.