11 Classes [class]

11.10 Comparisons [class.compare]

A defaulted equality operator function ([over.binary]) shall have a declared return type bool.

A defaulted == operator function for a class C is defined as deleted unless, for each

x_{i}

in the expanded list of subobjects for an object x of type C,

x_{i} == x_{i}

The return value of a defaulted == operator function with parameters x and y is determined by comparing corresponding elements

x_{i}

and

y_{i}

in the expanded lists of subobjects for x and y (in increasing index order) until the first index i where

x_{i} == y_{i}

yields a result value which, when contextually converted to bool, yields false.

The return value is false if such an index exists and true otherwise.

[Example 1: struct D { int i; friend bool operator==(const D& x, const D& y) = default; // OK, returns x.i == y.i }; — end example]