NUMBERS-207: Incorrect comparison of negative fractions.

Author: Gilles Sadowski

commons-numbers-fraction/src/main/java/org/apache/commons/numbers/fraction/BigFraction.java

@@ -1064,7 +1064,9 @@ public int compareTo(final BigFraction other) {
         // Compare absolute magnitude
         final BigInteger nOd = numerator.abs().multiply(other.denominator.abs());
         final BigInteger dOn = denominator.abs().multiply(other.numerator.abs());
-        return nOd.compareTo(dOn);
+        return lhsSigNum > 0 ?
+            nOd.compareTo(dOn) :
+            dOn.compareTo(nOd);
     }
 
     /**

commons-numbers-fraction/src/main/java/org/apache/commons/numbers/fraction/Fraction.java

@@ -876,7 +876,9 @@ public int compareTo(Fraction other) {
         // Multiplication by the signum is equal to the absolute.
         final long nOd = ((long) numerator) * lns * other.denominator * rds;
         final long dOn = ((long) denominator) * lds * other.numerator * rns;
-        return Long.compare(nOd, dOn);
+        return lhsSigNum > 0 ?
+            Long.compare(nOd, dOn) :
+            Long.compare(dOn, nOd);
     }
 
     /**

commons-numbers-fraction/src/test/java/org/apache/commons/numbers/fraction/BigFractionTest.java

@@ -254,6 +254,8 @@ void testCompareTo() {
         final BigFraction e = BigFraction.of(1, -2);
         final BigFraction f = BigFraction.of(-1, -2);
         final BigFraction g = BigFraction.of(-1, Integer.MIN_VALUE);
+        final BigFraction h = BigFraction.of(-2, 1);
+        final BigFraction i = BigFraction.of(-1, 1);
 
         Assertions.assertEquals(0, a.compareTo(a));
         Assertions.assertEquals(0, a.compareTo(c));
@@ -272,6 +274,7 @@ void testCompareTo() {
         Assertions.assertEquals(-1, g.compareTo(f));
         Assertions.assertEquals(1, a.compareTo(g));
         Assertions.assertEquals(-1, d.compareTo(g));
+        Assertions.assertEquals(-1, h.compareTo(i)); // JIRA:NUMBERS-207
 
         Assertions.assertEquals(0, BigFraction.of(0, 3).compareTo(BigFraction.of(0, -2)));
 

commons-numbers-fraction/src/test/java/org/apache/commons/numbers/fraction/FractionTest.java

@@ -214,6 +214,8 @@ void testCompareTo() {
         final Fraction e = Fraction.of(1, -2);
         final Fraction f = Fraction.of(-1, -2);
         final Fraction g = Fraction.of(-1, Integer.MIN_VALUE);
+        final Fraction h = Fraction.of(-2, 1);
+        final Fraction i = Fraction.of(-1, 1);
 
         Assertions.assertEquals(0, a.compareTo(a));
         Assertions.assertEquals(0, a.compareTo(c));
@@ -232,6 +234,7 @@ void testCompareTo() {
         Assertions.assertEquals(-1, g.compareTo(f));
         Assertions.assertEquals(1, a.compareTo(g));
         Assertions.assertEquals(-1, d.compareTo(g));
+        Assertions.assertEquals(-1, h.compareTo(i)); // JIRA:NUMBERS-207
 
         Assertions.assertEquals(0, Fraction.of(0, 3).compareTo(Fraction.of(0, -2)));