What is Expressiveness in a Computer Language

[Andreas Rossberg]

Darren New wrote:
> 
>> Maybe I don't understand what you mean with ADT here, but all 
>> languages with a decent module system support ADTs in the sense it is 
>> usually understood, see ML for a primary example.
> 
> OK.  Maybe some things like ML and Haskell and such that I'm not 
> intimately familiar with do, now that you mention it, yes.

Well, Modula and CLU already had this, albeit in restricted form.

>> Classes in most OOPLs are essentially beefed-up ADTs as well.
> 
> Err, no. There's nothing really abstract about them. And their values 
> are mutable. So while one can think about them as an ADT, one actually 
> has to write code to (for example) calculate or keep track of how many 
> entries are on a stack, if you want that information.

Now you lost me completely. What has mutability to do with it? And the 
stack?

AFAICT, ADT describes a type whose values can only be accessed by a 
certain fixed set of operations. Classes qualify for that, as long as 
they provide proper encapsulation.

>> Not counting C/C++, I don't know when I last worked with a typed 
>> language that does *not* have this ability... (which is slightly 
>> different from ADTs, btw)
> 
> Java? C#? Icon? Perl? (Hmmm... Pascal does, IIRC.)  I guess you just work
> with better languages than I do. :-)

OK, I admit that I exaggerated slightly. Although currently I'm indeed 
able to mostly work with the more pleasant among languages. :-)

(Btw, Pascal did not have it either, AFAIK)

- Andreas