11 Classes [class]

11.11 Comparisons [class.compare]

11.11.2 Equality operator [class.eq]

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}

is usable ([class.compare.default]).

The return value V 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.

If no such index exists, V is true.

Otherwise, V is false.

[Example

struct D {
  int i;
  friend bool operator==(const D& x, const D& y) = default;
                                                // OK, returns x.i == y.i
};

— end example

]