# [Tutor] the binary math "wall"

Dave Angel davea at ieee.org
Wed Apr 21 12:46:31 CEST 2010

Lowell Tackett wrote:
> --- On Tue, 4/20/10, Steven D'Aprano <steve at pearwood.info> wrote:
>
>
>> From: Steven D'Aprano <steve at pearwood.info>
>>
>> <snip>
>>
>> The simplest, roughest way to fix these sorts of problems
>> (at the risk
>> of creating *other* problems!) is to hit them with a
>> hammer:
>>
>>
>>>>> round(18.15*100) == 1815
>>>>>
>> True
>>
>
> Interestingly, this is the [above] result when I tried entered the same snippet:
>
> Python 2.5.1 (r251:54863, Oct 14 2007, 12:51:35)
> [GCC 3.4.1 (Mandrakelinux 10.1 3.4.1-4mdk)] on linux2
>
>>>> round(18.15)*100 == 1815
>>>>
> False
>
>
> <snip>
But you typed it differently than Steven.  He had   round(18.15*100),
and you used round(18.15)*100

Very different.   His point boils down to comparing integers, and when
you have dubious values, round them to an integer before comparing.  I
have my doubts, since in this case it would lead to bigger sloppiness
than necessary.

round(18.154 *100) == 1815

probably isn't what you'd want.

So let me ask again, are all angles a whole number of seconds?  Or can
you make some assumption about how accurate they need to be when first
input (like tenths of a second, or whatever)?  If so use an integer as
follows:

val =  round((((degrees*60)+minutes)*60) + seconds)*10)

The 10 above is assuming that tenths of a second are your quantization.

HTH
DaveA