Re: [boost] Interval Library and comparison operators

From: Sylvain Pion (pion_at_[hidden])
Date: 2002-09-06 11:00:39

On Fri, Sep 06, 2002 at 11:18:44AM -0400, David Bergman wrote:
> I definitely vote for having the lexicographic ordering being the
> default one, for all us STLish developers. It should be noted, and
> understood, that the purpose of that ordering is to enforce a total
> ordering for STL and similar purposes, and is in no way a
> domain-specific statement about intervals for arithmetics.
>
> If developers want domain-relevant relations, he/she should define them
> (or Boost.IntervalArithmetic could provide some useful ones, as given by
> Joel's disection)

I disagree.
I think that the default, if there is one, should be useful for the _primary_
usage of intervals.  And IMHO, this primary usage is not going to be 'using
the STL stuff "blindly"' by "us all STLish developpers".

If someone has a need for intervals, it is motivated _first_ by some
"domain-relevant" stuff.  Hence I think the default is related to that.
This is what is going to drive you to choose the correct Comparison_policy.

Do you use std::complex just to store a pair of floats ?  No.

The discussion shows that operator< and std::less are stuck to each other.
And I think it is much more useful to have a default that works well for the
usage of operator< (related to the primary usage of intervals), than for
STL's default arguments in some containers.

So I am still on the position that there should either be no default
Comparison_policy, or that the default should be to throw an exception for the
overlap case (and usual total order for the rest of the domain).

-- 
Sylvain