Built-in Mathematica Symbol

StringExpression (~~)

s₁~~s₂~~... or StringExpression[s₁, s₂, ...]
represents a sequence of strings and symbolic string objects s_i.

"str₁"~~"str₂"~~... yields an ordinary string obtained by concatenating the characters in the "str_i".

	"string"	a literal string of characters
	_	any single character
	__	any substring of one or more characters
	___	any substring of zero or more characters
	x_, x__, x___	substrings given the name x
	x:pattern	pattern given the name x
	pattern..	pattern repeated one or more times
	pattern...	pattern repeated zero or more times
	{patt₁, patt₂, ...} or patt₁\|patt₂\|...	a pattern matching at least one of the patt_i
	patt/;cond	a pattern for which cond evaluates to True
	pattern?test	a pattern for which test yields True for each character
	Whitespace	a sequence of whitespace characters
	NumberString	the characters of a number
	DatePattern[spec]	the characters of a date
	charobj	an object representing a character class (see below)
	RegularExpression["regexp"]	substring matching a regular expression
	StringExpression[...]	an arbitrary string expression

	{c₁,c₂,...}	any of the "c_i"
	Characters["c₁c₂..."]	any of the "c_i"
	CharacterRange["c₁","c₂"]	any character in the range "c₁" to "c₂"
	DigitCharacter	digit 0-9
	LetterCharacter	letter
	WhitespaceCharacter	space, newline, tab or other whitespace character
	WordCharacter	letter or digit
	Except[p]	any character except ones matching p

	StartOfString	start of the whole string
	EndOfString	end of the whole string
	StartOfLine	start of a line
	EndOfLine	end of a line
	WordBoundary	boundary between word characters and others
	Except[WordBoundary]	anywhere except a word boundary

When constructs like __ or .. are present, there may be several different ways in which a given StringExpression can match a particular string.

By default, Mathematica will use the one that makes pattern elements that appear earlier in the StringExpression match the longest possible substrings.

The following determine which match will be used if there are several possibilities:

	Shortest[p]	the shortest consistent match for p
	Longest[p]	the longest consistent match for p (default)

In matching ordinary expressions instead of strings, the shortest instead of the longest consistent match is used.

StringExpression objects can be used in many string manipulation functions, including StringReplace, StringCases, StringSplit and StringMatchQ.

A string expression representing the string "ab" followed by any single character:

Give all pairs of identical characters in the string: