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In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
Many trim functions have an optional parameter to specify a list of characters to trim, instead of the default whitespace characters. For example, PHP and Python allow this optional parameter, while Pascal and Java do not. With Common Lisp's string-trim function, the parameter (called character-bag) is required.
Neither Common Lisp nor Scheme has anything corresponding to null. The test "null" tests something for being the empty list, Python [], a value which is false in Common Lisp and true in Scheme. It has nothing to do with Python None, C NULL, or Java and C# null. --John Cowan 12:50, 13 October 2019 (UTC)
The keyword create introduces a list of procedures which can be used to initialize instances. In this case the list includes default_create, a procedure with an empty implementation inherited from class ANY, and the make procedure coded within the class.
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.
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)".
An empty string is encoded as 0:. The string "bencode" is encoded as 7:bencode. Lists are encoded as l<elements>e. Begins with l and ends with e. Elements are bencoded values concatenated without delimiters. Examples: An empty list is encoded as le. A list containing the string "bencode" and the integer -20 is encoded as l7:bencodei-20ee.
The strings over an alphabet, with the concatenation operation, form an associative algebraic structure with identity element the null string—a free monoid. Sets of strings with concatenation and alternation form a semiring, with concatenation (*) distributing over alternation (+); 0 is the empty set and 1 the set consisting of just the null ...