Re: [boost] Infinite precision integer draft

From: Marsh J. Ray (marsh.boost_at_[hidden])
Date: 2006-06-01 16:03:41

Topher Cooper wrote:
> <>
>
> The problem seems to me to be the idea that it inherits from integer 
> -- an almost classic example of misuse of inheritance.  Pardon me if 
> I lost the thread somewhere but that seems to be what is being proposed.
>
> As others have said, inheritance should represent ISA both in 
> interface and conceptually.  If unsigned_integer followed this 
> relationship than there would be no argument here -- the negative of 
> an unsigned_integer would be clearly and unambiguously defined -- it 
> just wouldn't happen to be an unsigned_integer.  But that seems to 
> eliminate the point of having a separate unsigned_integer 
> type.  Inheriting unsigned_integer from integer means that I can 
> never be sure that negating an integer (which might actually be an 
> unsigned_integer) is a reasonable thing to do.  VERY BAD DESIGN.
>   
Seems to me that, if the author is really set on using inheritance here, 
integer should inherit from unsigned_integer, since integer can do 
everything that an unsigned can do, but not vice-versa. Integer extends 
unsigned with the ability to represent negative values and the result of 
subtraction.

- Marsh