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12.2 Generic Bodies

(1)

The body of a generic unit (a generic body) is a template for the instance bodies. The syntax of a generic body is identical to that of a nongeneric body.

Dynamic Semantics

(2)

The elaboration of a generic body has no other effect than to establish that the generic unit can from then on be instantiated without failing the Elaboration_Check. If the generic body is a child of a generic package, then its elaboration establishes that each corresponding declaration nested in an instance of the parent (see 10.1.1) can from then on be instantiated without failing the Elaboration_Check.

NOTES

(3)

(4) The syntax of generic subprograms implies that a generic subprogram body is always the completion of a declaration.

Examples

(4)

Example of a generic procedure body:

(5)
       procedure Exchange(U, V : in out Elem) is  -- see 12.1
          T : Elem;  --  the generic formal type
       begin
          T := U;
          U := V;
          V := T;
       end Exchange;

(6)

Example of a generic function body:

(7)
       function Squaring(X : Item) return Item is  --  see 12.1
       begin
          return X*X;  --  the formal operator "*"
       end Squaring;

(8)

Example of a generic package body:

(9)
       package body On_Vectors is  --  see 12.1
(10)
          function Sum(A, B : Vector) return Vector is
             Result : Vector(A'Range); --  the formal type Vector
             Bias   : constant Integer := B'First - A'First;
          begin
             if A'Length /= B'Length then
                raise Length_Error;
             end if;
(11)
             for N in A'Range loop
                Result(N) := Sum(A(N), B(N + Bias)); -- the formal function Sum
             end loop;
             return Result;
          end Sum;
(12)
          function Sigma(A : Vector) return Item is
             Total : Item := A(A'First); --  the formal type Item
          begin
             for N in A'First + 1 .. A'Last loop
                Total := Sum(Total, A(N)); --  the formal function Sum
             end loop;
             return Total;
          end Sigma;
       end On_Vectors;

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