leerho commented on a change in pull request #369:
URL: https://github.com/apache/datasketches-java/pull/369#discussion_r733220950
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File path: src/main/java/org/apache/datasketches/tuple/Intersection.java
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@@ -107,14 +107,19 @@ public void intersect(final Sketch<S> tupleSketch) {
if (tupleSketch == null) { throw new SketchesArgumentException("Sketch
must not be null"); }
final boolean firstCall = firstCall_;
firstCall_ = false;
+ final boolean emptyIn = tupleSketch.isEmpty();
+ if (empty_ || emptyIn) { //empty rule
+ //Because of the definition of null above and the Empty Rule (which is
OR), empty_ must be true.
+ //Whatever the current internal state, we make our local empty.
+ resetToEmpty();
+ return;
Review comment:
There are two sets of "rules" for determining Theta and Empty for all
the Set Operations:
Empty Rules:
UNION: AND the empty states
Intersection: OR the empty states
AnotB: Whatever A is
Theta Rule (All set ops)
Result Theta = min(Theta A, Theta B)
These are derived from the theory in the Theta Sketch Framework, but not
explicitly stated as such in the TSF paper. I derived these rules from the
paper some years ago so I wouldn't have to keep returning back to the theory to
figure out how to implement the logic.
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