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C++: Maps on Chains
(From a conversation with Vassil Vassilev.) Suppose we want to have a C++ map where the keys are disjoint, integer intervals of the form [ a...
In layman terms, a strict weak order < behaves as the "less than" relationship does for numbers, except that there may be incomparable elements x, y such that x ≮ y and y ≮ x; for numbers, this only happens if x= y, but in the case of a general SWO we allow for distinct, incomparable elements as long as they form equivalence classes. In mathematical terms, our relationship is of a more general type called a strict partial order. A strict reading of the standard would not allow this workaround, as it is required that the comparison object for the map induce a strict weak ordering for all possible values of Key, not only those in the container (or that is my interpretation, at least): for all practical purposes, though, this works and will foreseeably continue to work for all future revisions of the standard.
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