[std-interval] Interval comparison operators

[first.i.last at comcast.net]

 -------------- Original message ----------------------
From: Guillaume Melquiond <guillaume.melquiond at ens-lyon.fr>
> Hi,

[...]

I expect to provide a detailed response, but I am confused by this section of your message:

> In particular, interval libraries usually provide explicit functions for
> comparing intervals, something like "certainly less than" or "possibly
> less than" functions that would always return a boolean value and never
> throw. We believe C++ features should be used to provide a nicer syntax
> though. Instead of cerlt(X,Y), a "certainly less than" comparison would
> then be written as:
> 
>         if (certainly(X < Y)) ...

Does this mean 

    if ( certainly_lt(X,Y) )

Or does operator<(interval,interval) return a specialized object that certainly(/*special object*/) reduces to a boolean or an exception?

If not, how do you expect the expression certainly(X<Y) to be evaluated?

-- Lee Winter