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1.6, tutorial, and floating point (was Re: varibles)

Simon Brunning SBrunning at trisystems.co.uk
Fri Sep 22 04:50:02 EDT 2000 
> From:	Brendhan Horne [SMTP:brendhan at bellsouth.net]
> 
> >>> tax = 17.5 / 100
> >>> price = 3.50
> >>> price * tax
> 0.6125
> >>> price + _
> 4.1125
> >>> round(_, 2)
> 4.11
> 
> What I ended up with when I did that was off by a miniscule amount and I
> was
> just wondering if it was do to editting needs (rounding numbers is not
> unusal in thing)
> or if I had done something wrong.
> 
Floating point numbers are inexact. From Kernighan and Plauger, The Elements
of Programming Style:

"As a wise programmer once said, 'Floating point numbers are like sandpiles:
every time you move one, you lose a little sand and you pick up a little
dirt'. And after a few computations, things can get pretty dirty."

If you want to *see* the number rounded, try something like:

print '%.2f' % round(_, 2)

Cheers,
Simon Brunning
TriSystems Ltd.
sbrunning at trisystems.co.uk

N.B. Sorry about the legal stuff - nothing I can do about it.




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