Re: Self-referential types

["Robert I. Eachus" <eachus@mitre.org>]

Brian Rogoff wrote:
 
> Does it discuss the detrimental effect on lots of other aspects of Ada
> when you remove nesting of procedures?

   Okay, I'll bite what are they?  Note that nesting of procedures
refers to
procedures declared inside other procedures, not procedures called
inside other procedures, or within packages.

   AFIAK, it is almost always poor engineering to declare procedures
within other procedures in Ada. The chief exception is recursive descent
parsers, and even in that case there are good arguments for using
unnested procedures.  Also there are cases where you want to break a
procedure into subunits for implementation reasons:

   procedure A (Some: Parameters) is
     Some_Local: Variables;
     procedure Start is separate;   -- Ed will write
     procedure Do_It is separate;   -- Joe is doing this
     procedure Cleanup is separate; -- Ed again
   begin Start; Do_It; Cleanup; end A;

   Often though, those separates disappear before the code is entered
into the CM system.  Ada lets fold called once procedures back in as
declare blocks with no change in semantic interpretation.

   Note also that I am talking about procedures.  Many (nested)functions
in Ada would be implemented in other languages as macros.  Using such
inlined functions is good programming practice in Ada.  

-- 

                                        Robert I. Eachus

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