# [Tutor] the binary math "wall"

Lowell Tackett lowelltackett at yahoo.com
Sun Apr 25 20:10:17 CEST 2010

```>From the virtual desk of Lowell Tackett

--- On Tue, 4/20/10, Steven D'Aprano <steve at pearwood.info> wrote:

> From: Steven D'Aprano <steve at pearwood.info>
> Subject: Re: [Tutor] the binary math "wall"
> To: tutor at python.org
> Date: Tuesday, April 20, 2010, 7:39 PM
> On Wed, 21 Apr 2010 02:58:06 am
> Lowell Tackett wrote:
> > I'm running headlong into the dilemma of binary math
> representation,
> with game-ending consequences, e.g.:
> > >>> 0.15

> But if you really need D.MMSS floats, then something like
> this should be
> a good start.:
>
> def dms2deg(f):
>     """Convert a floating point number formatted
> as D.MMSS
>     into degrees.
>     """
>     mmss, d = math.modf(f)
>     assert d == int(f)
>     if mmss >= 0.60:
>         raise ValueError(
> < .60 but got %f' % mmss)
>     mmss *= 100
>     m = round(mmss)
>     if m >= 60:
> expected < 60 but got %d' % m)
>     s = round((mmss - m)*100, 8)
>     if not 0 <= s < 60.0:
> expected < 60.0 but got %f' % s)
>     return d + m/60.0 + s/3600.0
>
>
> >>> dms2deg(18.15)
> 18.25
> >>> dms2deg(18.1515)
> 18.254166666666666
>
>

Haven't gone away...I'm having a blast dissecting (parsing[?]-is that the right word?) your script snippet!  Got a big pot of coffee fueling the effort.

>
> Note though that this still fails with some valid input. I
> will leave
> fixing it as an exercise (or I might work on it later, time
>
> permitting).

Got the hint...I'm gonna pick up this challenge.  This effort is taking me in endless tangents (all productive)-I'll be back sometime [soon] with my efforts and results.  Thanks for your [own] time and effort.

>
>
> --
> Steven D'Aprano
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```