Re: Overflow Test for M*/

On 13/07/2024 10:18 pm, Krishna Myneni wrote:

On 7/13/24 02:15, mhx wrote:

On Sat, 13 Jul 2024 2:03:54 +0000, dxf wrote:
>
[..]

How many applications have you written requiring a negative divisor?

>
I note that in the 68 occurrences of M*/ inside about 1900 files,
32 appear as ".. 1 M*/ ..".
>

 
The use of 1 M*/ just points to a missing factor of M*/ being omitted from the standard. In kForth, we provide the missing factor:
 
DS* ( d n -- t )
 
where t is a signed triple length product. Therefore, 1 M*/ can be replaced by
 
DS* drop
 
and the division can be avoided.
 
If you need an overflow check, it may be a bit more complicated, though.

Conversely one might factor >NUMBER :

: MU* ( ud1 u -- ud2 )  tuck * >r um* r> + ;

So far I've not needed a signed version...