Re: Comments on generic stack?

[gauthier@unilim.fr (Michel Gauthier)]

In article <4i6l2t$j1q@dmsoproto.ida.org>, wheeler@aphrodite.csed.ida.org
(David Wheeler) wrote:

>> [...]
>>  
>>  Below is yes, yet another implementation of an unbounded stack. This one
>>  supports assignment (:=), equality (=), and finalizes correctly, as
>>  well as supporting the tried and true Pop and Push operations.
>>  It's a generic that requires the Item to have := and =, but since the
>>  stack itself has those operations it is composable (you can have a
>>  Stack of Stacks of Integers).

Sorry to disturb, but I cannot understand what is a stack of stacks.

Stacks are designed to organise values, not objects. 
Stacks are objects, not values.
How can you define stacks of stacks ?

David probably means either stacks of (item=>references to stacks) or stacks of
(item=> some implementation of the stack abstract type with an initial algebra
behaviour). The latter actual type is an academic feature that has strictly no 
practical use.

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