Re: [boost] Infinite precision integer draft

From: Topher Cooper (topher_at_[hidden])
Date: 2006-06-01 17:18:51

That's really an issue of utility: Is the additional utility (which 
some seem to feel is essentially zero) it provides worth the 
additional complexity?

A general range restriction wrapper, as suggested, might give you 
more bang for the buck, but support for unsigned integer is not just 
another range restriction.  Non-negative integers -- i.e., numbers 
representing cardinality how *many* of some kind of thing there is -- 
is a uniquely useful and meaningful range restriction with special 
mathematical and practical properties.  It isn't "just" a range 
restriction of integers.  In fact, historically, the opposite is the 
case: the integers were an extension of the counting numbers.  Much 
of the utility of range restriction will come out of range 
restrictions based on cardinality (e.g., the number of elements in a 
collection, or the number of ASCII characters), for example, so most 
use of range restricted integers would conceptually be range 
restrictions of unsigned integers whether or not those are 
instantiated as a separate type.

In other words, a range restriction of 0..infinity is a "natural", 
useful and broadly meaningful, while a range restriction of, say 
-13..87 is arbitrary, and only useful and meaningful within a some 
restricted context.

That isn't to say its worth implementing separately, however.  Its 
just that its the same kind of question as whether its worth having 
an externally visible implementation of indefinite magnitude integer 
if you are going to have indefinite precision/magnitude rationals.

Topher

At 03:46 PM 6/1/2006, you wrote:
>Topher Cooper <topher_at_[hidden]> writes:
>
> > I don't think anyone really objects to unsigned_integer, though some
> > question its utility.
>
>I do object.  IMO it adds complexity for little or no benefit, and
>complexity is a big problem.  Also, in my opinion, the job of limiting
>the allowed range of values for a type should be provided by a wrapper
>template, so that other types can benefit.  For example:
>
>   typedef range_checked<
>       infinite_precision_integer
>     , non_negative  // a predicate
>   > infinite_precision_unsigned_integer;
>
>   typedef range_checked<
>       double
>     , abs_less_or_equal_to_1
>   > result_of_sin_or_cos;
>
>--
>Dave Abrahams
>Boost Consulting
>www.boost-consulting.com
>
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