OpenEuphoria

Re: [EuForum] Definition of insanity...

• Posted by CoJaBo <CoJaBo_EUforum_Address at CJBN.net> Nov 24, 2004
• 552 views

Pete Lomax wrote:
> 
> On Tue, 23 Nov 2004 14:14:41 -0800, CoJaBo <guest at RapidEuphoria.com>
> wrote:
> 
> >You must never have done this:
> >}}}
<eucode>
> >for o=1 to rand(1000000)*100 do
> >	--It doesnt seem to happen
> >	--unless the program runs for a while
> >end for
> >integer g
> >g=time()*100
> >?g
> >include get.e
> >?wait_key()
> ></eucode>
{{{

> >Run it a few times, you'll eventually get a fairly unexpected error!
> >This was the cause of headaches for many weeks before I figured it out...
> 
> I assume you mean that:
> 	g=floor(time()*100)
> 
> is occasionally (and seemingly against the docs) required?
> 
> If so, and having run the above several times, I'm slightly confused.
> Compare this to:
> 
> }}}
<eucode>
> if 0.1+0.2!=0.3 then
> 	puts(1,"not equal!\n")
> end if
> </eucode>
{{{

> 
> Which fails (100%) because (eg) 0.1 cannot be *exactly* represented in
> binary floating point (a hardware thing, not a dig at RDS). What
> confuses me is your code does not fail very often...
The origanal program went unchanged for months
before the problem appeared. At first it happened only
about 1% of the time, but eventually increased to 95%!
This change was what really confused me. Eu also kept
writing garbage to ex.err, making it even more confusing!

After it was finally fixed, I wanted to tar-and-feather
the creater of floating point!

> 
> Try this (failed 2dp atoms shown on the right, apologies for the line
> wrap):
> }}}
<eucode>
> procedure t100(sequence a)
> integer i
> 	for j=1 to length(a) do
> 		i=a[j]*100
> 		?i
> 	end for
> end procedure
> t100({1.90,1.91,1.92,1.93,1.94,1.95,1.96,1.97,1.98,1.99,	-- <none>
> 	  2.00,2.00,2.02,2.02,2.04,2.04,2.06,2.06,2.08,2.09,	--2.01,
> 2.03, 2.05, 2.07
> 	  2.10,2.11,2.12,2.13,2.14,2.15,2.16,2.17,2.17,2.19,	--2.18,
> 	  2.21,2.21,2.21,2.23,2.23,2.25,2.25,2.27,2.27,2.29,	--2.20,
> 2.21, 2.24, 2.25, 2.28
> 	  2.29,2.29,2.29,2.29,2.34,2.34,2.36,2.36,2.38,2.38,	--2.30,
> 2.31, 2.32, 2.33, 2.35, 2.37, 2.39
> 	  2.40,2.40,2.42,2.42,2.44,2.44,2.46,2.46,2.48,2.48,	--2.41,
> 2.42, 2.45, 2.47, 2.48
> 	  2.50,2.50,2.52,2.52,2.54,2.54,2.56,2.57,2.58,2.59,	--2.51,
> 2.53, 2.55
> 	  2.60,2.61,2.62,2.63,2.64,2.65,2.66,2.67,2.68,2.69,	-- <none>
> 	  2.70,2.71,2.72,2.73,2.74,2.75,2.76,2.77,2.78,2.79})	-- <none>
> </eucode>
{{{

> 
> I am *NOT* saying this can be fixed (apart from use of floor()),
> I am just exploring this in detail.
> It's a fairly strange spread, if anything can be read into that...
> Does anyone regularly using another language get the same results?
> 
> Yours curiously,
> Pete
> 
>