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  2. Language Integrated Query - Wikipedia

    en.wikipedia.org/wiki/Language_Integrated_Query

    GroupBy The GroupBy operator takes a function that extracts a key value and returns a collection of IGrouping<Key, Values> objects, for each distinct key value. The IGrouping objects can then be used to enumerate all the objects for a particular key value. Distinct The Distinct operator removes duplicate instances of an object from a collection.

  3. JavaScript syntax - Wikipedia

    en.wikipedia.org/wiki/JavaScript_syntax

    Variables in standard JavaScript have no type attached, so any value (each value has a type) can be stored in any variable. Starting with ES6 , the 6th version of the language, variables could be declared with var for function scoped variables, and let or const which are for block level variables.

  4. Group by (SQL) - Wikipedia

    en.wikipedia.org/wiki/Group_by_(SQL)

    A GROUP BY statement in SQL specifies that a SQL SELECT statement partitions result rows into groups, based on their values in one or several columns. Typically, grouping is used to apply some sort of aggregate function for each group. [1] [2] The result of a query using a GROUP BY statement contains one row for

  5. Subset sum problem - Wikipedia

    en.wikipedia.org/wiki/Subset_sum_problem

    Let A be the sum of the negative values and B the sum of the positive values; the number of different possible sums is at most B-A, so the total runtime is in (()). For example, if all input values are positive and bounded by some constant C , then B is at most N C , so the time required is O ( N 2 C ) {\displaystyle O(N^{2}C)} .

  6. pandas (software) - Wikipedia

    en.wikipedia.org/wiki/Pandas_(software)

    By default, a Pandas index is a series of integers ascending from 0, similar to the indices of Python arrays. However, indices can use any NumPy data type, including floating point, timestamps, or strings. [4]: 112 Pandas' syntax for mapping index values to relevant data is the same syntax Python uses to map dictionary keys to values.

  7. Tagged union - Wikipedia

    en.wikipedia.org/wiki/Tagged_union

    If an element lies in both, there will be two effectively distinct copies of the value in A + B, one from A and one from B. In type theory, a tagged union is called a sum type. Sum types are the dual of product types. Notations vary, but usually the sum type A + B comes with two introduction forms inj 1: A → A + B and inj 2: B → A + B.

  8. Algebraic data type - Wikipedia

    en.wikipedia.org/wiki/Algebraic_data_type

    The set of all possible values of a product type is the set-theoretic product, i.e., the Cartesian product, of the sets of all possible values of its field types. The values of a sum type are typically grouped into several classes, called variants. A value of a variant type is usually created with a quasi-functional entity called a constructor ...

  9. Data type - Wikipedia

    en.wikipedia.org/wiki/Data_type

    The standard type hierarchy of Python 3. In computer science and computer programming, a data type (or simply type) is a collection or grouping of data values, usually specified by a set of possible values, a set of allowed operations on these values, and/or a representation of these values as machine types. [1]