Ada 2005 Reference Manual

12.2 Generic Bodies

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

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

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

Examples

Example of a generic procedure body:

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;

Example of a generic function body:

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

Example of a generic package body:

package body On_Vectors is -- see 12.1

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;

for N in A'Range loop
Result(N) := Sum(A(N), B(N + Bias)); -- the formal function Sum
end loop;
return Result;
end Sum;

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;