Re: Sometimes Forth is just fun!

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From	minforth <minforth@gmx.net>
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Subject	Re: Sometimes Forth is just fun!
Date	Tue, 19 May 2026 20:19:09 +0200
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Am 19.05.2026 um 15:43 schrieb Hans Bezemer:
> After all that IEEE-754 stuff, I had to do something with it. Because 
> there was something I wanted to do for a long time - if just to honor 
> the programmers that came up with it:
> 
> : finvsqrt                             ( f -- 1/sqrt f)
>    fdup f>ieee-sf 2/ negate 1597463007 + ieee-sf>f
>    fswap f2/ fover fdup f* f* fnegate 3 s>f f2/ f+ f*
> ;
> 
> 16 s>f finvsqrt f. cr depth . fdepth .
> 
> And it does this:
> 
> $ pp4th -x zenisqrt.4th
> 0.249576787396195506538282980998661071
> 0 0
> 
> :-)
> 
> Hans Bezemer

Thanks for this little piece of nostalgia  :-)

Some background:
https://en.wikipedia.org/wiki/Fast_inverse_square_root

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Sometimes Forth is just fun! Hans Bezemer <the.beez.speaks@gmail.com> - 2026-05-19 15:43 +0200
  Re: Sometimes Forth is just fun! minforth <minforth@gmx.net> - 2026-05-19 20:19 +0200

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