Re: some questions re. Ada/GNAT from a C++/GCC user

[mab@dst17.wdl.loral.com (Mark A Biggar)]

In article <ROGOFF.96Mar29163036@sccm.Stanford.EDU> rogoff@sccm.stanford.edu writes:
>   > Why doesn't Ada 95 allow declarations to be interspersed with ordinary
>   > statements as C++ does?  (Or does it?  _Ada as a Second Language_ is a
>   > big book!)  It seems to me that the C++ approach is a small but
>   > definite win.  Does it interact very badly somehow with all those
>   > guarantees on elaboration order?
>
>   To intersperse declarations, you have to use a block_statement, like
>   this:
>
>       for I in Some_String'Range loop -- I wish I could easily use an iterator here ;-)
>	   declare
>	       X: constant Character := Some_String(I);
>	   begin
>	       ...
>	   end;
>       end loop;
>
>   To me, the "declare", "begin", and "end" are just useless verbosity.
>   I prefer the C++ rule.
>
>Yes, this seems needlessly verbose. Any Ada guru have a good reason why it has 
>to be this way?

Yeah, 2 reasons.  The first goes clear back to the original Ada Strawman
documnt which calls for a clear distinction between declarations and code
statements.  The second reason is that is also the method of wraping an
exception handler around soem arbitary piece of code:

for I in Some_String'Range loop 
    declare
        X: constant Character := Some_String(I);
    begin
        ...
    exception
        when ... ;
    end;
end loop;


--
Mark Biggar
mab@wdl.loral.com