+ /* The most intuitive understanding of the to_introduce counter is
+ * that it's tracking never-before-learned items as they are
+ * pulled from the bin with score 0. But that bin can become
+ * empty. So the refined rule is that we decrement to_introduce
+ * whenever we pull from the lowest-indexed bin with a
+ * non-negative score. */
+ if (mnemon->to_introduce && bin->score >=0 &&
+ (bin_index == 0 || mnemon->bins[bin_index-1].score < 0))
+ {
+ mnemon->to_introduce--;
+ }
+