[jira] [Commented] (MATH-754) Additional Fraction Constructor

["Gilles (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MATH-754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13216767#comment-13216767 ] 

Gilles commented on MATH-754:
-----------------------------

Hello.

At first glance, I'm not favorable to this addition. The reason is that IMHO Commons Math is a library that models mathematical objects and that the preconditions are dictated by the inherent limitations of those objects (or their numerical implementation). In the case which you present here, the limitation is imposed by the caller and has nothing to do with the called code ("Fraction").
One way to deal with your high-level requirement is to create a class that will inherit from CM "Fraction"; the constructor of your class will thus check the precondition that is now specific to the object which this new class is meant to model (a fraction with a controlled set of denominators).

Whether that new class will be a useful addition to the library is another issue.

                
> 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.

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