Fix BoundedRational normalization
Bug: 31035142
Change maybeReduce to a static function, so that we can deal correctly
with results that might already be null.
Fix maybeReduce so that it actually returns the reduced result, not
the original. This was an undetected bug that I think only has
performance implications, and that only under conditions that are
unlikely for the calculator. Nonetheless the original code was
pretty silly.
Add tests for the original bug and other conceivable issues in that
vicinity.
Change-Id: I982dbbaff22f6b05f71a101fee38b25d527ed967
diff --git a/src/com/android/calculator2/BoundedRational.java b/src/com/android/calculator2/BoundedRational.java
index e9e6f05..f2f7185 100644
--- a/src/com/android/calculator2/BoundedRational.java
+++ b/src/com/android/calculator2/BoundedRational.java
@@ -170,18 +170,19 @@
static Random sReduceRng = new Random();
/**
- * Return a possibly reduced version of this that's not tooBig().
+ * Return a possibly reduced version of r that's not tooBig().
* Return null if none exists.
*/
- private BoundedRational maybeReduce() {
+ private static BoundedRational maybeReduce(BoundedRational r) {
+ if (r == null) return null;
// Reduce randomly, with 1/16 probability, or if the result is too big.
- if (!tooBig() && (sReduceRng.nextInt() & 0xf) != 0) {
- return this;
+ if (!r.tooBig() && (sReduceRng.nextInt() & 0xf) != 0) {
+ return r;
}
- BoundedRational result = positiveDen();
+ BoundedRational result = r.positiveDen();
result = result.reduce();
if (!result.tooBig()) {
- return this;
+ return result;
}
return null;
}
@@ -225,7 +226,7 @@
}
final BigInteger den = r1.mDen.multiply(r2.mDen);
final BigInteger num = r1.mNum.multiply(r2.mDen).add(r2.mNum.multiply(r1.mDen));
- return new BoundedRational(num,den).maybeReduce();
+ return maybeReduce(new BoundedRational(num,den));
}
/**
@@ -265,7 +266,7 @@
}
static BoundedRational multiply(BoundedRational r1, BoundedRational r2) {
- return rawMultiply(r1, r2).maybeReduce();
+ return maybeReduce(rawMultiply(r1, r2));
}
public static class ZeroDivisionException extends ArithmeticException {