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luc edited comment on MATH181 at 1/31/08 2:39 PM:

I have checked the ideas I had about denominator. They do not address your issue, so the patch
as applied is good.
However, I noticed the last statement in the private constructor was a call to reduce. This
seems strange to me because a known property of the recursive algorithm to build the convergents
cn=pn/qn is that they are already reduced. This is a result of applying the Bezout theorem
to the easily proved recursive property p(n)q(n1)  p(n1)q(n) = (1)^(n+1). This property
holds even if a1 is completely wrong due to numerical errors.
When I remove this statement, the existing test succeed as expected. I did not find any related
information in the log message nor in JIRA.
May I remove this statement or did I miss something ?
was (Author: luc):
I have checked the ideas I had about denominator. They are do not address your issue,
so the patch as applied is good.
However, I noticed the last statement in the private constructor was a call to reduce. This
seems strange to me because a known property of the recursive algorithm to build the convergents
cn=pn/qn is that they are already reduced. This is a result of applying the Bezout theorem
to the easily proved recursive property p(n)q(n1)  p(n1)q(n) = (1)^(n+1). This property
holds even if a1 is completely wrong due to numerical errors.
When I remove this statement, the existing test succeed as expected. I did not find any related
information in the log message nor in JIRA.
May I remove this statement or did I miss something ?
> Specify the maximum of digits when parsing a Fraction
> 
>
> Key: MATH181
> URL: https://issues.apache.org/jira/browse/MATH181
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 1.1
> Reporter: Niall Pemberton
> Priority: Minor
> Attachments: MATH181FractionDigitsLimitv2.patch, MATH181FractionDigitsLimit.patch,
MATH181FractionMaxDenominator.patch
>
>
> Firstly, thanks for the Fraction code  I've adapated it for something I'm working on
and I didn't have a clue how to convert a decimal to a fraction :)
> Excel spreadsheets have the facility to specify a fraction format where you specify the
maximum number of denominator digits to display.
> So for example:
> format "?/?" displays decimal values formatted in the range 1/2 to n/9
> format "??/??" displays decimal values formatted in the range 1/2 to n/99
> format "???/???" displays decimal values formatted in the range 1/2 to n/999 etc
> In excel then the value 0.6152 displays as 3/5, 8/13 and 510/829 respectively for the
above 3 formats.
> I'm attaching a patch for the Fraction class which adds a new constructor where the maximum
number of digits can be specified, rather than the epsilon value.

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