Overloading of Operators
Author: JTC1/SC22/WG9/ARG, by Randall Brukardt, ARG Editor

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# 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

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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

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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.
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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).
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An explicit declaration of "/=" shall not have a result type of the predefined type Boolean.

#### Static Semantics

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A declaration of "=" whose result type is Boolean implicitly declares a declaration of "/=" that gives the complementary result.
NOTES
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8 The operators "+" and "-" are both unary and binary operators, and hence may be overloaded with both one- and two-parameter functions.

#### Examples

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Examples of user-defined operators:
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`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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