RE: BUG! Erratic for loop behavior
On 25 Mar 2002, at 11:04, dm31 at uow.edu.au wrote:
>
> > That is one heck of a sentence! After 3 minutes, i am still
> re-reading it to see
> > if i really know what you meant.
> >
> > Kat
>
> Sorry Kat,
> Early morning is not a good time for making sense.
Same here. After 2am, there's no telling what i'll type.
> What i'm saying is a floating point number is stored in two parts
> 1. the mantissa
> 2. the exponent
>
> an example is the 0.1 is stored as 1 x 10^-1
> thus the mantissa is 1 and the exponent is -1
> so using a 8-bit float as an example 0.1 in binary is
>
> 0001 and 1111(-1 in 2's complement)
>
> So storing numbers like 0.1, 0.3 and 0.01 completely accurately should
> not be a problem. It is only a problem in 'larger' decimal numbers.
>
> for i = 31.4 to 31.5 do... should work perfectly. Or am I just been
> dumb?
I wouldn't use the word "dumb". But consider the fraction 1/3. in decimal it's
0.3333333333333333-> infinity. How can that be represented in binary? It
can't. It's only perfectly accurate in base3 or integer multiples of 3. I think
i
remember an experimental computer that used 3 voltage levels per bit, but it
was slow and buggy, and that's all i remember of it. Back in the 8087@1mhz
days, i considered using analog carry-forward lines in an adder using a
74F181, which would have beat the socks off any 8087 i ever saw, but by
today's standards, it would be insanely slow. As slow as string math. The
best i know of in hardware for decimal math is BCD encoded
representations, but atm i can't recall any hardware in use today that has it.
The 8087 didn't. The Turbo Pascal runtime math lib didn't have it. But i
ramble... i didn't sleep at all lastnite.
Kat
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