C++ concepts: LessThanComparable
From cppreference.com
                    
                                        
                    
                    
                                                            
                    The type must work with < operator and the result should have standard semantics.
[edit] Requirements
| Expression | Requirements | Return type | 
|---|---|---|
| a < b | 
 (strict weak ordering relation)  | 
bool or a type implicitly convertible to bool |