Domain basis: Difference between revisions
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If you happen to already be familiar with [[temperament merging]], merging<ref>The technical mathematical term for this is "sumset", not "union" as we might expect; in many contexts, "union" is the dual operation to "intersection", but for vector spaces, the dual operation to intersection is "sumset" (see page 4 of https://www2.math.upenn.edu/~siegelch/Notes/linalg.pdf). The difference between union and sumset can be explained like this: if we had two planes in a volume, their union would be both the planes, but their sumset would be the volume.</ref> interval bases follows a similar pattern: concatenate, then canonicalize the result. | If you happen to already be familiar with [[temperament merging]], merging<ref>The technical mathematical term for this is "sumset", not "union" as we might expect; in many contexts, "union" is the dual operation to "intersection", but for vector spaces, the dual operation to intersection is "sumset" (see page 4 of https://www2.math.upenn.edu/~siegelch/Notes/linalg.pdf). The difference between union and sumset can be explained like this: if we had two planes in a volume, their union would be both the planes, but their sumset would be the volume.</ref> interval bases follows a similar pattern: concatenate, then canonicalize the result. | ||
== Notation == | |||
The notation for merging is the same as comma-merge: <math>B_1|B_2</math><ref>Using ∩ for intersection, which seems obvious. But the merge notation is tricky. We could use ∪, of course. But technically speaking, it's not a union, but a sumset, and the notation for that is unfortunately just the plus sign +, which could be confusing. Furthermore, in the context of merging temperaments, we don't use either of those symbols. Actually, we use two different symbols there, depending on what we're merging! We use & if it's maps, and | if it's commas. At least, that's the notation used on the [[Meet and join]] and [[Temperament merging]] pages. And because intersections also arise for temperament matrices like mappings and comma bases, this article has gone with consistent notation for interval bases. Interval bases concatenate horizontally, like comma bases, so we use | and consider it a "basis-merge" symbol, i.e. it works on both comma bases and interval bases.</ref>. | |||
== Concatenate == | == Concatenate == | ||
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# The results we want are in the bottom-right. We take only half-columns, from the bottom half, and only half-columns where their corresponding top-half are all zeros (which will only happen to columns that are sorted to the right side). | # The results we want are in the bottom-right. We take only half-columns, from the bottom half, and only half-columns where their corresponding top-half are all zeros (which will only happen to columns that are sorted to the right side). | ||
# Canonicalize. | # Canonicalize. | ||
== Notation == | |||
The notation for interval basis intersecting is just the intersection symbol: <math>B_1∩B_2</math>. | |||
== Example == | == Example == | ||