[interchange-bugs] [rt.icdevgroup.org #349] Vend::Util::round_to_frac_digits() simplification

[Mark Overmeer via RT]

<URL: http://rt.icdevgroup.org/Ticket/Display.html?id=349 >

* Peter Ajamian via RT (interchange at rt.icdevgroup.org) [120321 19:25]:
> peter at peter-desktop:~$ perl -le 'print sprintf "%.*f", 2, 0.125'
> 0.12
> peter at peter-desktop:~$ perl -le 'print sprintf "%.*f", 2, 0.1251'
> 0.13
> 
> ... Definate rounding error there and there are other examples as well,
> and I wish the national debt was 12 cents.

It is not a rounding error in sprintf here, but in converting 0.125 into a
floating-point number.  Probably it gets converted into 0.12499999999999
When you round that, you get 0.12 as shown.

So, you indicate a common problem with floats.  Two solutions:
  . always administer money as integer cents
  . add 0.001 to sprintf (which I forgot in my original bug-report)

 markov at moon> perl -le 'print sprintf "%.*f", 2, 0.125 +0.001'
 0.13
 markov at moon> perl -le 'print sprintf "%.*f", 2, 0.1251 + 0.0001'
 0.13

The standard conversion routine from float to string in Perl does the
same thing.
-- 
Regards,
               MarkOv

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       Mark Overmeer MSc                                MARKOV Solutions
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