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The empty string has several properties: |ε| = 0. Its string length is zero. ε ⋅ s = s ⋅ ε = s. The empty string is the identity element of the concatenation operation. The set of all strings forms a free monoid with respect to ⋅ and ε. ε R = ε. Reversal of the empty string produces the empty string, so the empty string is a palindrome.
The class null is a subclass of the symbol class, because nil is a symbol. Since nil also represents the empty list, null is a subclass of the list class, too. Methods parameters specialized to symbol or list will thus take a nil argument. Of course, a null specialization can still be defined which is a more specific match for nil.
MySQL provides an enumerated type ENUM with allowable values specified as strings when a table is created. The values are stored as numeric indices with the empty string stored as 0, the first string value stored as 1, the second string value stored as 2, etc. Values can be stored and retrieved as numeric indexes or string values. [10] Example:
A string s is said to be a substring or factor of t if there exist (possibly empty) strings u and v such that t = usv. The relation "is a substring of" defines a partial order on Σ *, the least element of which is the empty string.
In object-oriented languages, string functions are often implemented as properties and methods of string objects. In functional and list-based languages a string is represented as a list (of character codes), therefore all list-manipulation procedures could be considered string functions.
In JavaScript, the empty string (""), null, undefined, NaN, +0, −0 and false [28] are sometimes called falsy (of which the complement is truthy) to distinguish between strictly type-checked and coerced Booleans (see also: JavaScript syntax#Type conversion). [29] As opposed to Python, empty containers (Arrays, Maps, Sets) are considered truthy.
A string is a substring (or factor) [1] of a string if there exists two strings and such that =.In particular, the empty string is a substring of every string. Example: The string = ana is equal to substrings (and subsequences) of = banana at two different offsets:
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. The C++ Boost library defines space characters according to locale , as well as offering variants with a predicate parameter (a functor ) to select which characters ...