Re: [Amforth-devel] printing floats

[Leon N M. <leo...@gm...>]

I did what I mentioned earlier and replaced the repeated division in FS. by 
repeated multiplication and one division. I didn't benchmark it rigorously, 
but it seems to be nearly as fast as the method where we multiply by 1/10, but 
it doesn't have the accuracy problems. For example:

The new method:
> _pi _1e3 f* fs.
3.1415925E3  ok
> _pi _1e3 f/ fs.
3.1415923E-3  ok

The multiply by 1/10 method:
> _pi _1e3 f* fs.
3.1415915E3  ok
> _pi _1e3 f/ fs.
3.1415923E-3  ok

So the new method restricts the error to the least significant digit printed, 
where as the multiply by 1/10 method does not.

Unless this turns out to be much slower than I expect, I'll run with this new 
method until f/ can be improved.

Any objections if I make the floating point code version 4.1 dependent so that 
I can use 2>R, 2R> and 2LITERAL?
-Leon

>Saturday 04 September 2010
>From: "pito" <pi...@vo...>
>Subject: Re: [Amforth-devel] printing floats
> Yes, 0.1 is $3dcccccc = 0.09999999403953552
> from that the result will be 3.14158984478e+/-15 (shall be
> 3.1415926535e+/-15).
> Our result is 3.1415851, or 3.1415874 - so quite precise. However, I
> would simply recommend to print with 4 decimal places only. For
> atmega users -3.1415E-27 might be ok, I guess. And nobody will be
> nervous (:-)). Q: can we set the number of decimal places to be
> print somehow? Pito