[
https://issues.apache.org/jira/browse/MATH-754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13216977#comment-13216977
]
Travis Hanna commented on MATH-754:
-----------------------------------
Oh, nothing is wrong with a subclass. This is the way I would have solved it
in the project I'm working on but in commons-math 2.2, Fraction is declared
final. Instead, I had to create a little utility class to generate these
fractions as a result. I figured other people have probably had the same
problem so I thought I might submit a patch back to try and be helpful.
In my last comment, I was speculating on whether or not it would be useful to
have a class that represents a Fraction with a constrained denominator and
maintains that constraint through whatever operations you might perform on it.
My gut says it wouldn't be all that useful though so I won't be creating one.
I think you have a valid point when you say I'm pushing higher level
requirements down into the Fraction class but I do have one counter argument.
These constructors all smell the same to me:
public Fraction(double value, double epsilon, int maxIterations)
public Fraction(double value, double epsilon, Set<Integer>
acceptableDenominators)
public Fraction(double value, int maxDenominator)
There's really no clean way to create a fraction from a double. In all three
cases, higher level requirements have seeped down into the library. The amount
of acceptable error and performance constraints are both higher level
requirements IMHO.
I won't be offended if my patch is rejected or anything. I just suspect other
people using the class probably have similar requirements.
Maybe there should be a separate class that is responsible for converting
doubles to Fractions to keep the Fraction class clean?
> Additional Fraction Constructor
> -------------------------------
>
> Key: MATH-754
> URL: https://issues.apache.org/jira/browse/MATH-754
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 3.0
> Environment: All
> Reporter: Travis Hanna
> Priority: Minor
> Labels: features, newbie, patch
> Fix For: 3.0
>
> Attachments: math.patch
>
>
> I'm writing some code which outputs fractional measurements meant for human
> consumption. I need a constructor for Fraction which allows you to restrict
> the denominators to a finite set. This is necessary due to the fact that
> real-world tools are only available with certain fractions. For example, it's
> next to impossible to find a ruler with 1/7 inch marked :).
> I'm attaching a patch which implements the functionality. I've attempted to
> mimic the style of the existing code as much as possible. One caveat: I don't
> speak French so the french error message is a computer-generated translation
> and probably very poor.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
