Re: exercise in double number arithmetic

On 7/7/24 00:48, Ahmed wrote:

On Sat, 6 Jul 2024 23:50:28 (UTC), Krishna Myneni wrote:
 

On 7/6/24 16:59, Ahmed wrote:

...

: solution ( -- d)
     1 s>d 43 22 do i 1 m*/ loop d>f
     21 dup s>d rot 2 do I 1 m*/ loop d>f
     f/ fround f>d ;
>

...

Krishna

  You have not to use fround. (42!/21!) is an integer and is multiple of
21!.
in other words 42! is multiple of (21!)^2.
 

The FROUND is necessary because 42!/21! is too large of an integer to be exactly represented by double-precision fp (IEEE format) and F>D is a truncating operation, not rounding.
The whole D>F and floating point operations can be dispensed with if we have D/MOD -- a double length version /MOD.
--
Krishna