[tpm] Talk topics

[Abram Hindle]

On 12-11-29 10:19 PM, Scott Elcomb wrote:
> On Thu, Nov 29, 2012 at 9:56 PM, Tom Legrady <legrady at gmail.com> wrote:
>> I can just imagine the CNC carving right through the object, pieces flying
>> in every direction, because you used the wrong browser.
> 
> Or client-side math...  :-)
> 
> 0.1 + 0.2 != 0.3 // true
> 

Watch out with floating point comparisons and floating point
accumulation too.

perl -e 'print abs((0.1 + 0.2) - 0.3)'
5.55111512312578e-17

python
Python 2.7.3 (default, Aug  1 2012, 05:14:39)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> abs((0.1 + 0.2) - 0.3)
5.551115123125783e-17

The page:

https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/

Shows:

Number          Value
0.1             0.1 (duh)
float(.1)       0.100000001490116119384765625
double(.1)      0.10000000000000000555111512312578270211815834045 41015625

And of course "What Every Computer Scientist Should Know About
Floating-Point Arithmetic"
http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

Summary: Floats are dangerous.

abram

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