Nested quote
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A nested quote is a quote that is encapsulated inside another quote, forming a hierarchy with multiple levels. When focusing on a certain quote, one must interpret it within its scope. Nested quotes can be used in literature (as in nested narration), speech, and computer science (as in "meta"-statements that refer to other statements as strings). Nested quotes can be very confusing until evaluated carefully and until each quote level is put into perspective.
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[edit] Convention
Normally, hierarchical quote sublevels alternate between using the quote delimiter '' (double quote) and ' (single quote). This is normally true, regardless of the quote style -- whether the start and end quote symbols are uniform (straight quotes) or different (smart quotes, with the quote symbols at the beginning and end pointing inwards in their respective directions towards the quote text). For straight quotes (normally used in plaintext), the alternation between single and double quotes is necessary. For smart quotes, it is not as necessary, since the directional quote symbols behave analogously to nested parentheses, since the delimeters are unique and it is clear where a quote opens (beginning a new sublevel) and ends (ending that sublevel and returning to the outer scope). However, convention dictates that alternating symbols are used either way.
[edit] Example in literature
In literature, a good example of a story that uses nested quotes throughout the entirety of its narration, is Heart of Darkness by Joseph Conrad. It can be very confusing to English classes because of its complex hierarchical structure of the narrator narrating in the first person, giving the majority of the story to dialog from one character (Marlow) who speaks in the first person, who quotes many other characters, and often quoting those characters' quotes of other characters.
Consider this example from that story (page 29): [Marlow said,] "...The fat man sighed. 'Very sad.' 'And the pestiferous absurdity of his talk,' continued the other; 'he bothered me enough when he was here. "Each station should be like a beacon on the road towards better things, a center for trade of course, but also for humanizing, improving, instructing." Conceive you--that [a**]! And he wants to be manager! No, it's--' Here he got choked by excessive indignation, and I lifted my head the least bit. ..."
Marlow is telling the story about a fat man sighing and another person talking about someone who says bothersome things. The latter person Marlow quotes, in turn, quotes the person he is talking about, leading to a 2nd-level nested quote.
[edit] Example in JavaScript programming
Nested quotes often become an issue using the eval keyword. The eval function is a function that converts and interprets a string as actual JavaScript code, and runs that code. If that string is specified as a literal, then the code must be written as a quote itself (and escaped accordingly).
For example:
eval("var a=3; alert();");
This code declares a variable a, which is assigned the value 3, and a blank alert window is popped up to the user.
[edit] Nested strings (level 2)
Suppose we had to make a quote inside the quoted interpreted code. In JavaScript, you can only have one unescaped quote sublevel, which has to be the alternate of the top-level quote. If the 2nd-level quote symbol is the same as the first-level symbol, these quotes must be escaped. For example:
alert("I don't need to escape here");
alert('Nor is it "required" here');
alert('But now I do or it won\'t work');
[edit] Nested strings (level 3 and beyond)
Furthermore (unlike in the literature example), the third-level nested quote must be escaped in order not to conflict with either the first- or second-level quote delimiters. This is true regardless of alternating-symbol encapsulation. Every level after the third level must be recursively escaped for all the levels of quotes in which it is contained. This includes the escape character itself, the backslash ("\"), which is escaped by itself ("\\").
For every sublevel in which a backslash is contained, it must be escaped for the level above it, and then all the backslashes used to escape that backslash as well as the original backslash, must be escaped, and so on and so forth for every level that is ascended. This is to avoid ambiguity and confusion in escaping.
Here are some examples that demonstrate some of the above principles:
document.write("<html><head></head><body><p>Hello, this is the body of the document.");
document.writeln("</p>");
docment.write("<p>A newline in HTML code
acts simply as whitespace, whereas a <br> starts a new line.");
document.write("</p></body></html>\n");
eval('eval(\"eval(\\\"alert(\\\\\\\"Now I\\\\\\\\\\\\\\\'m confused!\\\\\\\")\\\")\")');
