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Concept
String literal
Summary
A string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo", where "foo" is a string literal with value foo. Methods such as escape sequences can be used to avoid the problem of delimiter collision (issues with brackets) and allow the delimiters to be embedded in a string. There are many alternate notations for specifying string literals especially in complicated cases. The exact notation depends on the programming language in question. Nevertheless, there are general guidelines that most modern programming languages follow.
Most modern programming languages use bracket delimiters (also balanced delimiters)
to specify string literals. Double quotations are the most common quoting delimiters used:
"Hi There!"
An empty string is literally written by a pair of quotes with no character at all in between:
""
Some languages either allow or mandate the use of single quotations instead of double quotations (the string must begin and end with the same kind of quotation mark and the type of quotation mark may or may not give slightly different semantics):
'Hi There!'
These quotation marks are unpaired (the same character is used as an opener and a closer), which is a hangover from the typewriter technology which was the precursor of the earliest computer input and output devices.
In terms of regular expressions, a basic quoted string literal is given as:
"[^"]*"
This means that a string literal is written as: a quote, followed by zero, one, or more non-quote characters, followed by a quote. In practice this is often complicated by escaping, other delimiters, and excluding newlines.
A number of languages provide for paired delimiters, where the opening and closing delimiters are different. These also often allow nested strings, so delimiters can be embedded, so long as they are paired, but still result in delimiter collision for embedding an unpaired closing delimiter.
Official source
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