6.6 Overloading of Operators

1. An operator is a function whose designator is an operator_symbol. Operators, like other functions, may be overloaded.
   Name Resolution Rules
   
2. Each use of a unary or binary operator is equivalent to a function_call with function_prefix being the corresponding operator_symbol, and with (respectively) one or two positional actual parameters being the operand(s) of the operator (in order).
   Legality Rules
   
3. The subprogram_specification of a unary or binary operator shall have one or two parameters, respectively. A generic function instantiation whose designator is an operator_symbol is only allowed if the specification of the generic function has the corresponding number of parameters.
4. Default_expressions are not allowed for the parameters of an operator (whether the operator is declared with an explicit subprogram_specification or by a generic_instantiation).
5. An explicit declaration of "/=" shall not have a result type of the predefined type Boolean.
   Static Semantics
   
6. A declaration of "=" whose result type is Boolean implicitly declares a declaration of "/=" that gives the complementary result.
   

   NOTES
   

7. (8) The operators "+" and "-" are both unary and binary operators, and hence may be overloaded with both one- and two-parameter functions.
   Examples
   
8. Examples of user-defined operators:

9. function "+" (Left, Right : Matrix) return Matrix;
   function "+" (Left, Right : Vector) return Vector;
   
   --  assuming that A, B, and C are of the type Vector
   --  the following two statements are equivalent:
   
   A := B + C;
   A := "+"(B, C);
   

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