How Can Tuples and `std::tie` Simplify Comparison Operator Implementation in C ?

Circumventing Comparison Operator Implementation with Tuples and Tie

When constructing lightweight structures containing only two elements, many developers opt for std::pair due to its built-in support for key operations such as operator< for strict-weak ordering. However, this approach presents drawbacks in the form of unhelpful variable naming that can lead to confusion. Nesting pairs becomes less desirable with more than two members.

An alternative solution involves employing tuples from Boost or C 11. While tuples offer improved structure and clarity compared to std::pair, they can still be cumbersome to utilize. To alleviate this issue, developers may consider using tie-based operations instead.

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);
}

In this instance, tie creates a tuple of references from the passed arguments. The benefits of this approach include:

• Simplified syntax for operator implementation
• Ability to exclude non-essential members from the ordering process

While privately inheriting from a tuple may be suggested as an alternative, it exhibits several drawbacks:

• Free-standing operators (or friends) require public inheritance
• Functions and operators can be bypassed through casting
• Certain members can be omitted from the ordering process with the tie solution

Overall, the implementation of comparison operators via tuples and tie presents a viable option for simplified and correct operator implementation. However, performance implications should be considered and addressed if profiling reveals that the comparison operation is a bottleneck in the application's execution.

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