[FRPythoneers] I must be sitting too close to the monitor.

ccollier at viawest.net ccollier at viawest.net
Thu Jan 13 10:31:03 MST 2005


interesting.  thanks for the input guys!

c

On Thu, 13 Jan 2005, Ben Harding wrote:

> What we call floating point numbers are a mapping of a continuous number 
> space (real numbers) into a discrete number space (integers.)  There are 
> holes in this map and some real numbers cannot be represented exactly.  
> The internal representation used by the machine or software does it's 
> best, but can't be perfect.
> 
> I bet there are others on this list that really know about this, and I 
> would be interested in learning more about the floating point 
> representation in general and that used by Python.
> 
> Ben
> 
> ccollier at viawest.net wrote:
> 
> >There is definitely something odd occuring.  First, note that it works if 
> >you use integers (say 5 and 1).  Also, note that it works if you start 
> >with change = 0.02.
> >
> >There is some interesting typing(?) occuring.  Here's a slightly modified 
> >version:
> >
> >host$ cat test.py 
> >change = 0.05
> >while change >= 0.01:
> >    print "a:", repr(change)
> >    change = change - 0.01 
> >    print "b:", (change)
> >    print
> >
> >
> >And the output with python 2.3:
> >
> >host$ python ./test.py 
> >a: 0.050000000000000003
> >b: 0.04
> >
> >a: 0.040000000000000001
> >b: 0.03
> >
> >a: 0.029999999999999999
> >b: 0.02
> >
> >a: 0.019999999999999997
> >b: 0.01
> >
> >
> >Anyone with some insight here?
> >
> >c
> >
> >
> >On Wed, 12 Jan 2005, Scott Durkin wrote:
> >
> >  
> >
> >>Hi,
> >>
> >>My apologies for posing a VERY low-level user question . . .
> >>
> >>I use (well, try to anyway) Python in a junior high class I teach.  
> >>I have a simple script and very dumb question . . . 
> >>
> >>SCRIPT:
> >>
> >>change = 0.05
> >>while change >= 0.01:
> >>    print change
> >>    change = change - 0.01 
> >>
> >>OUTPUT:
> >>
> >>0.05
> >>0.04
> >>0.03
> >>0.02
> >>
> >>QUESTION:
> >>
> >>Why doesn't "0.01" appear in the output?!?!?!
> >>
> >>Thank you for any help you could give me!
> >>
> >>Scott Durkin
> >>
> >>__________________________________________________________________________
> >>    _____        ___     __   __   
> >>   /____/ \     /_ /|   /_/| /_/| Scott Durkin - sdurkin at psdschools.org
> >>  |  __ \ /|    | | |  | |__| | |
> >>  | |__) |/  /|_| | |  |  __  | |           Computer Science
> >>  |  ___/   ||__| | |  | | || | |         Preston Junior High
> >>  |_|/      |_____|/   |_|/ |_|/                                         
> >>                                  http://staffweb.psdschools.org/sdurkin
> >>             2004-05                           970.419.7358
> >>
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> >>    
> >>
> >
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> >
> 
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