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  2. Lower limit topology - Wikipedia

    en.wikipedia.org/wiki/Lower_limit_topology

    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).

  3. Interval (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Interval_(mathematics)

    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.

  4. Partially ordered set - Wikipedia

    en.wikipedia.org/wiki/Partially_ordered_set

    The half-open intervals [a, b) and (a, b] are defined similarly. Whenever a ≤ b does not hold, all these intervals are empty. Every interval is a convex set, but the converse does not hold; for example, in the poset of divisors of 120, ordered by divisibility (see Fig. 7b), the set {1, 2, 4, 5, 8} is convex, but not an interval.

  5. Half-open - Wikipedia

    en.wikipedia.org/wiki/Half-open

    Half-open may refer to: Half-open file in chess; Half-open vowel, a class of vowel sound; ... Half-open interval, an interval containing only one of its endpoints;

  6. Derived set (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Derived_set_(mathematics)

    If is endowed with its usual Euclidean topology then the derived set of the half-open interval [,) is the closed interval [,]. Consider R {\displaystyle \mathbb {R} } with the topology (open sets) consisting of the empty set and any subset of R {\displaystyle \mathbb {R} } that contains 1.

  7. General topology - Wikipedia

    en.wikipedia.org/wiki/General_topology

    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 ...

  8. Zero-based numbering - Wikipedia

    en.wikipedia.org/wiki/Zero-based_numbering

    Discussing possible designs of array ranges by enclosing them in a chained inequality, combining sharp and standard inequalities to four possibilities, demonstrating that to his conviction zero-based arrays are best represented by non-overlapping index ranges, which start at zero, alluding to open, half-open and closed intervals as with the ...

  9. Borel measure - Wikipedia

    en.wikipedia.org/wiki/Borel_measure

    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 ...