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But {{{1|}}} will evaluate to the empty string (a false value) because the vertical bar or pipe character, "|", immediately following the parameter name specifies a default value (here an empty string because there is nothing between the pipe and the first closing curly brace) as a "fallback" value to be used if the parameter is undefined.
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.
Note that a null set is not necessarily an empty set. Common notations for the empty set include "{}", "∅", and " ∅ {\displaystyle \emptyset } ". The latter two symbols were introduced by the Bourbaki group (specifically André Weil ) in 1939, inspired by the letter Ø in the Danish and Norwegian alphabets (and not related in any way to the ...
A whitespace character is a character data element that represents white space when text is rendered for display by a computer.. For example, a space character (U+0020 SPACE, ASCII 32) represents blank space such as a word divider in a Western script.
In SQL, wildcard characters can be used in LIKE expressions; the percent sign % matches zero or more characters, and underscore _ a single character. Transact-SQL also supports square brackets ([and ]) to list sets and ranges of characters to match, a leading caret ^ negates the set and matches only a character not within the list.
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 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 prefix [1] of a string if there exists a string such that =. A proper prefix of a string is not equal to the string itself; [2] some sources [3] in addition restrict a proper prefix to be non-empty. A prefix can be seen as a special case of a substring.