QPartialOrdering Class

Detailed Description

A value of type QPartialOrdering is typically returned from a three-way comparison function. Such a function compares two objects, and it may either establish that the two objects are ordered relative to each other, or that they are not ordered. The QPartialOrdering value returned from the comparison function represents one of those possibilities.

The possible values of type QPartialOrdering are, in fact, fully represented by the following four static values:

• QPartialOrdering::Less represents that the first object is less than the second;
• QPartialOrdering::Equivalent represents that the first object is equivalent to the second;
• QPartialOrdering::Greater represents that the first object is greater than the second;
• QPartialOrdering::Unordered represents that the first object is not ordered with respect to the second.

QPartialOrdering is idiomatically used by comparing an instance against a literal zero, for instance like this:

// given a, b, c, d as objects of some type that allows for a 3-way compare,
// and a compare function declared as follows:

QPartialOrdering compare(T lhs, T rhs); // defined out-of-line
~~~

QPartialOrdering result = compare(a, b);
if (result < 0) {
    // a is less than b
}

if (compare(c, d) >= 0) {
    // c is greater than or equal to d
}

A QPartialOrdering value which represents an unordered result will always return false when compared against literal 0.