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The lower limit topology is finer (has more open sets) than the standard topology on the real numbers (which is generated by the open intervals). The reason is that every open interval can be written as a (countably infinite) union of half-open intervals. For any real and , the interval [,) is clopen in (i.e., both open and closed).
In summary, a set of the real numbers is an interval, if and only if it is an open interval, a closed interval, or a half-open interval. [4] [5] A degenerate interval is any set consisting of a single real number (i.e., an interval of the form [a, a]). [6] Some authors include the empty set in this definition.
While there are many Borel measures μ, the choice of Borel measure that assigns ((,]) = for every half-open interval (,] is sometimes called "the" Borel measure on . This measure turns out to be the restriction to the Borel σ-algebra of the Lebesgue measure λ {\displaystyle \lambda } , which is a complete measure and is defined on the ...
With zero-based numbering, a range can be expressed as the half-open interval, [0, n), as opposed to the closed interval, [1, n]. Empty ranges, which often occur in algorithms, are tricky to express with a closed interval without resorting to obtuse conventions like [1, 0].
Half-open interval, an interval containing only one of its endpoints; Half-open line segment, a line segment containing only one of its endpoints; TCP half-open, a TCP connection out of synchronization
A classical example is to define a content on all half open intervals [,) by setting their content to the length of the intervals, that is, ([,)) =. One can further show that this content is actually σ-additive and thus defines a pre-measure on the semiring of all half-open intervals.
Given the closed interval [,] of the real number line, the open sets of the topology are generated from the half-open intervals (,] with < and [,) with >.The topology therefore consists of intervals of the form [,), (,), and (,] with < <, together with [,] itself and the empty set.
The set of all open intervals forms a base or basis for the topology, meaning that every open set is a union of some collection of sets from the base. In particular, this means that a set is open if there exists an open interval of non zero radius about every point in the set. More generally, the Euclidean spaces R n can be given a topology. In ...