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12.2 Generic Bodies
1
{generic body} 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].
1.a
Ramification: We also
use terms like ``generic function body'' and ``nongeneric package body.''
Dynamic Semantics
2
{elaboration (generic body)
[partial]} 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.
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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