Implementing comparision operators via 'tuple' and 'tie', a good idea?
- by Xeo
(Note: tuple and tie can be taken from Boost or C++11.)
When writing small structs with only two elements, I sometimes tend to choose a std::pair, as all important stuff is already done for that datatype, like operator< for strict-weak-ordering.
The downsides though are the pretty much useless variable names. Even if I myself created that typedef, I won't remember 2 days later what first and what second exactly was, especially if they are both of the same type. This gets even worse for more than two members, as nesting pairs pretty much sucks.
The other option for that is a tuple, either from Boost or C++11, but that doesn't really look any nicer and clearer. So I go back to writing the structs myself, including any needed comparision operators.
Since especially the operator< can be quite cumbersome, I thought of circumventing this whole mess by just relying on the operations defined for tuple:
Example of operator<, e.g. for strict-weak-ordering:
bool operator<(MyStruct const& lhs, MyStruct const& rhs){
return std::tie(lhs.one_member, lhs.another, lhs.yet_more) <
std::tie(rhs.one_member, rhs.another, rhs.yet_more);
}
(tie makes a tuple of T& references from the passed arguments.)
Edit: The suggestion from @DeadMG to privately inherit from tuple isn't a bad one, but it got quite some drawbacks:
If the operators are free-standing (possibly friends), I need to inherit publicly
With casting, my functions / operators (operator= specifically) can be easily bypassed
With the tie solution, I can leave out certain members if they don't matter for the ordering
Are there any drawbacks in this implementation that I need to consider?
