[cmucl-imp] [cmucl-help] NaN

[Marco Antoniotti]

> On Jan 10, 2017, at 16:46 , Raymond Toy <toy.raymond at gmail.com> wrote:
...
> 
>    Marco> Well.  I have been fooling around (read: veered off a
>    Marco> tangent) with interval arithmetic, where it looks like you
>    Marco> need to ensure that your rounding modes are set to positive
>    Marco> or negative infinity when using an end points
>    Marco> representation.  That’s were it all started.
> 
> That's one way. I vaguely recall some Fortran TOMS package that
> included interval arithmetic, but I think it just did something simple
> like multiply by 1+e for some tiny e.
> 
> Setting the rounding modes twice (up and down) for every operation is
> pretty expensive.

Ok.  I presume that the references talk of rounding modes only because they assume some “very-close-to-the-metal” implementation.

In any case, the need for NaNs and infinities is there.  And right now CL is lacking in this respect.

Cheers

--
Marco Antoniotti