Thu, 11 Nov 2004 14:33:44 +0100
Roger Racine writes:
> At 01:04 PM 11/10/2004 -0800, Prichard, Jayson (Space Technology) wrote:
>>I am writing a subroutine that has one parameter, another subroutine that
>>I want the second subroutine to execute. Does anyone have any ideas how
>>to do this?
> Ada95 or Ada83? With Ada95 it is quite straightforward (see section 3.10
> of the Reference Manual). You simply create an access type and use the
> access type as the parameter.
> type procedure_access is access procedure (. . .);
> procedure my_proc (proc_access : in procedure_access);
> procedure real_proc (...) -- same arguments as in the type declaration
> my_proc (real_proc'access);
> For Ada83, it could still be done for all the compilers I used, but was
> implementation dependent. As I recall, one used the 'address of the
> procedure, and then used a representation clause to call the procedure.
> Roger Racine
Another way is to use a generic:
procedure Test is
with procedure To_Be_Called (The_Parameter : in Whatever);
procedure Generic_Proc is
To_Be_Called (The_Parameter => ...);
procedure First (The_Parameter : in Whatever) is separate;
procedure Second is new Generic_Proc (To_Be_Called => Second);
begin -- Test
Generics are usually preferred to access-to-subprograms because they
are safer since no null access value can ever exist.