Is Using `std::tie` for Tuple Comparison in C a Sensible Approach?

Implementing Comparison Operators with Tuples and Ties a Sensible Approach?

When faced with small structs consisting of merely two elements, many opt for standard pairs due to the pre-defined necessities, such as the strict-weak ordering operator. However, this approach presents challenges with its uninformative variable names, particularly when dealing with multiple elements or nested pairs.

An alternative is to utilize tuples, either from Boost or C 11. While they offer a cleaner look, they still involve complexities when comparing. Seeking a more streamlined solution, some consider circumventing this by relying solely on tuple operations.

For instance, a strict-weak ordering operator can be written using a tie, which forms a tuple of T&A references from the provided arguments:

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);
}

This elegant approach allows for easy comparison operations. However, it's still important to consider drawbacks. One concern is when operators are free-standing or friends, in which case public inheritance may be necessary. This can lead to vulnerabilities where functions or operators (specifically operator=) could be bypassed. Additionally, ties may exclude members that are irrelevant for ordering, potentially introducing complications.

Ultimately, the decision to utilize this approach should be based on its performance implications. While it certainly simplifies the operator code, concerns arise if profiling indicates a time-consuming comparison operation. Otherwise, the ease of maintenance may outweigh any potential drawbacks.

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