Re: advantages or disadvantages of ADA over pascal or modula

[Ted Dennison <dennison@telepath.com>]

Alfred Hilscher wrote:
> Compared to Modula-2 I see the following disadvantages:
> 
> - No _real_ hidden export. You can define types to be "private" in your
> spec, but if you want change the definition (let's say from a pointer to
> a four byte hash key), you have to change the package spec (= DEFINITION
> MODULE) and then recompile _all_ importing modules (although it's only
> an internal change to your implementation).


Actually, the difference isn't all that great. To make the type hidden 
in Modula-2, it has to be of a type that can fit in a register (numeric 
or pointer). To get the effect with record types, you have to use a 
pointer as the type in the interface. In Ada you can effect the same 
thing with access types by deferring the definition of the object they 
point to into the package body. All you are missing is the ability to do 
something similar with numeric types. Its not really *that* different.