Re: Callback in Ada

["Randy Brukardt" <randy@rrsoftware.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccmxngzc0x.fsf@shell01.TheWorld.com...
...
> Others argued that we don't want to give people the ability to
> completely dispense with Ada's separation of spec and body.
> Also, the expression function syntax is nice for short
> "one liners", where the extra verbiage of "begin" and
> "end Blah;" is just noise.

To expand on this a bit.

Ada always has had the ability to put arbitrary expressions into package 
specifications (default expressions, initializing expressions, etc.). This 
new capability just provides a way to give those expressions a convinient 
name.

OTOH, Ada only has one way to put a body into a package specification (via a 
generic instantiation - and it is rarely used for this purpose). Adding more 
ways to put a body into a package specification seems to change the model of 
the language, and might also pose new implementation difficulties 
(implementations might somehow depend on the absence of bodies). Indeed, it 
is likely that there are language rules which depend on this absence (I 
distinctly remember a freezing rule that only works because there cannot be 
a procedure call in a package specification, although I wasn't able to turn 
up a reference to that). So allowing full bodies in package specifications 
is a lot more risky than just allowing expressions.

                                Randy.