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+%
+% File: QUOTE.TEX
+%
+% Author: Hunter Goatley
+% goathunter@goatley.com
+%
+% Date: August 14, 1991
+%
+% Abstract:
+%
+% This file defines the macros \begindoublequotes and \enddoublequotes,
+% which let TeX replace the double-quote character (") with TeX's
+% left double-quote and right double-quote. For example:
+%
+% "This is a test." ---> ``This is a test.''
+%
+% The double-quote character is still available via \dq. (\" is still
+% treated as the umlaut accent.)
+%
+% This macro makes a couple of assumptions about the double-quotes:
+%
+% 1. Double-quotes are assumed to come in pairs. When replacing
+% double-quotes, the macro alternates between `` and ''. The only
+% exception to this is noted in (2) below.
+% 2. A double-quote at the beginning of a paragraph is always treated
+% as ``. This correctly handles the case where a quotation is
+% continued into a second paragraph:
+%
+% "This is the first paragraph.\par
+% "This is the second paragraph of the same quote."
+%
+% Normal TeX spacing after `` and '' is maintained by saving and
+% restoring the \spacefactor.
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% HOW IT WORKS:
+%
+% The double-quote character (") is made active by \begindoublequotes.
+% The " macro keeps track of left-quote/right-quote pairs and inserts
+% the appropriate `` and '' in its place.
+%
+% Each character has a \spacefactor associated with it, which specifies
+% the amount of stretch or shrink that a space following the character
+% can have. Most characters have a factor of 1000, but some punctuation
+% marks have higher spacefactors, most notably the period, which has a
+% \spacefactor of 3000. This means the space following a period can
+% stretch up to 3 times more than the space after a regular character,
+% accounting for the increased space at the end of sentences.
+%
+% The `` and '' ligatures are assigned \spacefactor's of 0, so that the
+% \spacefactor that is applied to the next character is the same as that
+% of the character preceding the quotes. Because " has been redefined as
+% a macro, any spaces following " are swallowed by TeX. It was necessary
+% to have this macro re-insert any needed space so that the following
+% cases worked correctly:
+%
+% "This is a test," she said. --> ``This is a test,'' she said.
+% "This is in a list"; etc. --> ``This is in a list''; etc.
+%
+% Without the added space, the first example becomes:
+%
+% ``This is a test,''she said.
+%
+% The solution was to save the current \spacefactor before inserting a
+% right double-quote, then resetting the \spacefactor after the
+% insertion. The net effect was that the " macro has a \spacefactor
+% of 0, which matches the way TeX treats `` and ''.
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+{% % Begin a group for which " is active
+\catcode`\"=\active % Make " an active character
+\catcode`\@=11 % Make @ an active character
+%
+% \begindoublequotes
+%
+% This macro makes " an active character, resets the control sequence
+% \dblqu@te to L (left), and defines \dq as a replacement for ".
+%
+\gdef\begindoublequotes{% % \begindoublequotes enables "
+ \global\catcode`\"=\active % Make " an active character
+ \global\chardef\dq=`\" % Double-quote char. via \dq
+ \global\let\dblqu@te=L % Always start with a left double-quote
+ } % End of macro
+%
+% Define the macro that will be executed whenever " is encountered.
+%
+\gdef"{%
+ % If the double-quote is the first character in a new paragraph,
+ % make sure it becomes a left double-quote. This case can be
+ % detected by checking to see if TeX is currently in vertical mode.
+ % If so, the double-quote is at the beginning of the paragraph
+ % (since " hasn't actually generated any horizontal mode tokens
+ % yet, TeX is still in vertical mode). If the mode is vertical,
+ % set \dblqu@te equal to L.
+ %
+ \ifinner\else\ifvmode\let\dblqu@te=L\fi\fi
+ %
+ % Now insert the appropriate left or right double-quote.
+ %
+ % If \dblqu@te is L, insert a `` and set \dblqu@te to R.
+ %
+ \if L\dblqu@te``\global\let\dblqu@te=R%
+ %
+ % Otherwise, save the current \spacefactor, insert '', set \dblqu@te
+ % to L, and reset the original \spacefactor.
+ %
+ \else
+ \let\xxx=\spacefactor % Save the \spacefactor
+ ''\global\let\dblqu@te=L% % Insert '' and reset \dblqu@te
+ \spacefactor\xxx % Reset the \spacefactor
+ \fi % End of \if L\dblqu@te...
+ } % End of " macro
+} % End of group
+
+\gdef\enddoublequotes{%
+ \catcode`\"=12 %Set " back to other
+ }