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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-181) Specify the maximum of digits when parsing a Fraction
Date Mon, 28 Jan 2008 12:07:37 GMT
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[ https://issues.apache.org/jira/browse/MATH-181?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12563124#action_12563124
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Luc Maisonobe commented on MATH-181:
------------------------------------

The patch has been commited as of r615856, including the addition of a check for denominatorDigits
value as suggested by Phil.

I will probably look more in depth on this issue, because I think some improvements can be
made. Continued fractions are a very efficient way to approximate doubles. Their accuracy
is linked to the *square* of the denominator of the first ignored term. So I think converting
the number of digits to a max denominator simply as 10^d is too much.

So I don't close the issue yet.

> Specify the maximum of digits when parsing a Fraction
> -----------------------------------------------------
>
>                 Key: MATH-181
>                 URL: https://issues.apache.org/jira/browse/MATH-181
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 1.1
>            Reporter: Niall Pemberton
>            Priority: Minor
>         Attachments: MATH-181-FractionDigitsLimit-v2.patch, MATH-181-FractionDigitsLimit.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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