Ada 2012 Reference Manual
6.3 Subprogram Bodies
A subprogram_body specifies the execution of a subprogram.
Syntax
subprogram_body ::=
[overriding_indicator]
subprogram_specification
[aspect_specification] is
declarative_part
begin
handled_sequence_of_statements
end [designator];
[overriding_indicator]
subprogram_specification
[aspect_specification] is
declarative_part
begin
handled_sequence_of_statements
end [designator];
If a designator appears at the end of a subprogram_body, it shall repeat the defining_designator of the subprogram_specification.
Legality Rules
In contrast to other bodies, a subprogram_body need not be the completion of a previous declaration, in which case the body declares the subprogram. If the body is a completion, it shall be the completion of a subprogram_declaration or generic_subprogram_declaration. The profile of a subprogram_body that completes a declaration shall conform fully to that of the declaration.
Static Semantics
A subprogram_body is considered a declaration. It can either complete a previous declaration, or itself be the initial declaration of the subprogram.
Dynamic Semantics
The elaboration of a nongeneric subprogram_body has no other effect than to establish that the subprogram can from then on be called without failing the Elaboration_Check.
The execution of a subprogram_body is invoked by a subprogram call. For this execution the declarative_part is elaborated, and the handled_sequence_of_statements is then executed.
Examples
Example of procedure body:
procedure Push(E : in Element_Type; S : in out Stack) is
begin
if S.Index = S.Size then
raise Stack_Overflow;
else
S.Index := S.Index + 1;
S.Space(S.Index) := E;
end if;
end Push;
begin
if S.Index = S.Size then
raise Stack_Overflow;
else
S.Index := S.Index + 1;
S.Space(S.Index) := E;
end if;
end Push;
Example of a function body:
function Dot_Product(Left, Right : Vector) return Real is
Sum : Real := 0.0;
begin
Check(Left'First = Right'First and Left'Last = Right'Last);
for J in Left'Range loop
Sum := Sum + Left(J)*Right(J);
end loop;
return Sum;
end Dot_Product;
Sum : Real := 0.0;
begin
Check(Left'First = Right'First and Left'Last = Right'Last);
for J in Left'Range loop
Sum := Sum + Left(J)*Right(J);
end loop;
return Sum;
end Dot_Product;
