[jira] Commented: (MATH-60) [math] Function math.fraction.ProperFractionFormat.parse(String, ParsePosition) return illogical result

["Phil Steitz (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/MATH-60?page=comments#action_12412099 ] 

Phil Steitz commented on MATH-60:
---------------------------------

Thank you for reporting this.  I agree that the treatment of minus signs in the fractional parts of mixed fractions is not correct.  I think, however, that the correct solution is to throw a ParseException when the fractional part is
negative.  Otherwise, we have to disambiguate expressions such as "-1 -1/3"  which could mean -4/3 or -2/3.  I think it is better to view these expressions as meaningless.  If there are no objections, I will make that change.

> [math] Function math.fraction.ProperFractionFormat.parse(String, ParsePosition) return illogical result
> -------------------------------------------------------------------------------------------------------
>
>          Key: MATH-60
>          URL: http://issues.apache.org/jira/browse/MATH-60
>      Project: Commons Math
>         Type: Bug

>     Versions: 1.1 Final
>  Environment: Operating System: other
> Platform: Other
>     Reporter: nhung.nnguyen

>
> Hello,
> I find illogical returned result from function "Fraction parse(String source, 
> ParsePostion pos)" (in class ProperFractionFormat of the Fraction Package) of 
> the Commons Math library. Please see the following code segment for more 
> details:
> "
> ProperFractionFormat properFormat = new ProperFractionFormat();
> result = null;
> String source = "1 -1 / 2";
> ParsePosition pos = new ParsePosition(0);
> //Test 1 : fail 
> public void testParseNegative(){
>  
>    String source = "-1 -2 / 3";
>    ParsePosition pos = new ParsePosition(0);
>    Fraction actual = properFormat.parse(source, pos);
>    assertNull(actual);
> }
> // Test2: success
> public void testParseNegative(){
>  
>    String source = "-1 -2 / 3";
>    ParsePosition pos = new ParsePosition(0);
>    Fraction actual = properFormat.parse(source, pos);  // return Fraction 1/3
>    assertEquals(1, source.getNumerator());
>    assertEquals(3, source.getDenominator());
> }
> "
> Note: Similarly, when I passed in the following inputs: 
>   input 2: (source = “1 2 / -3”, pos = 0)
>   input 3: ( source = ” -1 -2 / 3”, pos = 0)
> Function "Fraction parse(String, ParsePosition)" returned Fraction 1/3 (means 
> the result Fraction had numerator = 1 and  denominator = 3)for all 3 inputs 
> above.
>  
> I think the function does not handle parsing the numberator/ denominator 
> properly incase input string provide invalid numerator/denominator. 
> Thank you!

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