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A list may contain the same value more than once, and each occurrence is considered a distinct item. A singly-linked list structure, implementing a list with three integer elements. The term list is also used for several concrete data structures that can be used to implement abstract lists, especially linked lists and arrays.
COBOL uses the STRING statement to concatenate string variables. MATLAB and Octave use the syntax "[x y]" to concatenate x and y. Visual Basic and Visual Basic .NET can also use the "+" sign but at the risk of ambiguity if a string representing a number and a number are together. Microsoft Excel allows both "&" and the function "=CONCATENATE(X,Y)".
In formal language theory and pattern matching (including regular expressions), the concatenation operation on strings is generalised to an operation on sets of strings as follows: For two sets of strings S 1 and S 2 , the concatenation S 1 S 2 consists of all strings of the form vw where v is a string from S 1 and w is a string from S 2 , or ...
Both maps and sets support bidirectional iterators. For more information on iterators, see Iterators. While not officially part of the STL standard, hash_map and hash_set are commonly used to improve searching times. These containers store their elements as a hash table, with each table entry containing a bidirectional linked list of elements
This is a list of well-known data structures. For a wider list of terms, see list of terms relating to algorithms and data structures. For a comparison of running times for a subset of this list see comparison of data structures.
A linked list is a sequence of nodes that contain two fields: data (an integer value here as an example) and a link to the next node. The last node is linked to a terminator used to signify the end of the list.
The definition of the list's elements. Expansion(s) of the list to generate fragments of declarations or statements. The list is defined by a macro or header file (named, LIST) which generates no code by itself, but merely consists of a sequence of invocations of a macro (classically named "X") with the elements' data.
[4]: 114 A DataFrame is a 2-dimensional data structure of rows and columns, similar to a spreadsheet, and analogous to a Python dictionary mapping column names (keys) to Series (values), with each Series sharing an index. [4]: 115 DataFrames can be concatenated together or "merged" on columns or indices in a manner similar to joins in SQL.