Sorensen–Dice coefficient: Difference between revisions

This is slightly different from the current draft task description, which suggests that <code>SDI = 2 × (A ∩ B) / (A ⊎ B)</code> produces a number between 0 and 1. If A and B are sets, each containing the same tokens, the result here would be 2 rather than 1. But we can make sense of this by assuming that the original algorithm was working with sequences rather than sets. The sequence difference is not commutative, so if <code>∩</code> represents sequence difference, and <code>⊎</code> represents sequence addition, it would make sense to define <code>SDI= ((A ∩ B) + (B ∩ A)) / (A ⊎ B)</code>, which is what we have done here (note that this change also includes an implicit shift from tokens to token counts somewhere in that calculation, as division only makes sense with numbers).