[jira] [Created] (NUMBERS-128) Precision of Fraction.floatValue() can be improved

["Heinrich Bohne (JIRA)" <ji...@apache.org>]

Heinrich Bohne created NUMBERS-128:
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             Summary: Precision of Fraction.floatValue() can be improved
                 Key: NUMBERS-128
                 URL: https://issues.apache.org/jira/browse/NUMBERS-128
             Project: Commons Numbers
          Issue Type: Improvement
          Components: fraction
    Affects Versions: 1.0
            Reporter: Heinrich Bohne


The current implementation of {{Fraction.floatValue()}} first calls {{doubleValue()}}, which converts the fraction to a {{double}} with maximum possible precision, and then rounds the returned {{double}} value to a {{float}}. For the fraction 1 + 2^6^ / (2^30^ - 1) = (2^30^ - 1 + 2^6^) / (2^30^ - 1), this yields a result of exactly 1. However, the [actual value of the fraction|https://www.wolframalpha.com/input/?i=(2%5E30+-+1+%2B+2%5E6)%2F(2%5E30+-+1)+to+base+2] is closer to 1 + 2^-23^ (which is representable exactly as a {{float}}) than it is to 1, as WolframAlpha [confirms|https://www.wolframalpha.com/input/?i=abs((2%5E30+-+1+%2B+2%5E6)%2F(2%5E30+-+1)+-+(1+%2B+2%5E-23))+%3C+abs((2%5E30+-+1+%2B+2%5E6)%2F(2%5E30+-+1)+-+1)].



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