6.6 Overloading of Operators
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Name Resolution Rules2
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).
function_callin most other language rules. However, as often happens, the equivalence is not perfect, as operator calls are not a
name, while a
name. Thus, operator calls cannot be used in contexts that require a
name(such as a rename of an object). A direct fix for this problem would be very disruptive, and thus we have not done that. However, qualifying an operator call can be used as a workaround in contexts that require a
subprogram_specification of a unary or binary operator shall have one or two parameters, respectively. The parameters shall be of mode in. 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, and they are all of mode in.
An explicit declaration of "/=" shall not have a result type of the predefined type Boolean.
An explicit declaration of "=" whose result type is Boolean implicitly declares an operator "/=" that gives the complementary result.
Examples of user-defined operators:
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);