Overview of User-Defined Operators

Operator members use reserved .OPERATOR... names.

Comparison operators

::rank STRUCT
{
  .value VAR I32;

  .OPERATOR<=> FUNCTION(@OTHER CONST& rank): ORDER
  {
    IF (.value < OTHER.value) { RETURN ORDER::LESS; }
    IF (.value > OTHER.value) { RETURN ORDER::GREATER; }
    RETURN ORDER::EQUAL;
  }
}

An .OPERATOR<=> definition can supply <, >, <=, and >= through comparison synthesis. .OPERATOR== similarly supplies equality and inequality.

RETURN_UNEQUAL shortens lexicographic three-way comparison:

::compare_pair FUNCTION(@left_a I32, @right_a I32,
                        @left_b I32, @right_b I32): ORDER
{
  RETURN_UNEQUAL left_a, right_a;
  RETURN_UNEQUAL left_b, right_b;
  RETURN ORDER::EQUAL;
}

Each statement returns immediately when its operands are unequal and otherwise continues to the next field.

Other operator members

Types may declare the operator members supported by their role, including:

• .OPERATOR() for callable objects;
• .OPERATOR-> for iterator dereference;
• .OPERATOR+= and .OPERATOR-= for iterator movement;
• .OPERATOR:= for assignment;
• .OPERATOR<-> for swap.

The declaration's parameters and receiver qualifier define the valid operand types. Operator overloading does not change precedence or invent unrelated control flow.

Reference

See the User-Defined Operators Reference for the complete language rules, constraints, and technical edge cases.