How to Define a Strict Weak Ordering `

Defining Operator < for Strict Weak Ordering on an n-tuple

Question:

How to implement the < operator for an n-tuple (e.g., 3-tuple) that adheres to the concept of strict weak ordering?

Answer:

Understanding Strict Weak Ordering

Strict weak ordering is a mathematical relation that defines a specific comparison between two objects:

• Equivalent: Both objects are considered equal (i.e., a < b and b < a are both false).
• Less Than: One object is considered "less than" the other (i.e., a < b is true and b < a is false).

Implementing the < Operator

To define the < operator for an n-tuple, you must establish the conditions that determine when one tuple is considered equivalent or less than another. This is dependent on the specific data structure and semantics of your tuple.

Example with std::tuple

The C Standard Library's std::tuple class implements a correct < operator for strict weak ordering. If you are unable to use this class, you can manually implement your own < operator:

struct S {
    ThingA a;
    ThingB b;
};

bool operator<(S const& lhs, S const& rhs) {
    return std::tie(lhs.a, lhs.b) < std::tie(rhs.a, rhs.b);
}

This assumes that ThingA and ThingB already implement strict weak ordering.

You can also implement equality using a similar approach:

bool operator==(S const& lhs, S const& rhs) {
    return std::tie(lhs.a, lhs.b) == std::tie(rhs.a, rhs.b);
}

The above is the detailed content of How to Define a Strict Weak Ordering `. For more information, please follow other related articles on the PHP Chinese website!