%%% @TeX-style-file
%%% {
%%% author = "Philip Taylor",
%%% version = "3.05",
%%% date = "7 April 2011",
%%% time = "15:59:31 BST",
%%% filename = "path.sty",
%%% license = "Unlimited copying and redistribution of this
%%% file are permitted as long as this file is
%%% not modified. Modifications are permitted,
%%% but only if the resulting file is not named
%%% path.sty regardless of case",
%%% address = "c/o The Hellenic Institute
%%% Royal Holloway, University of London
%%% Egham Hull, Egham
%%% Surrey TW20 0EX
%%% United Kingdom",
%%% telephone = "Tel: +44 1622 820 735",
%%% email = "P.Taylor@Rhul.Ac.Uk",
%%% codetable = "ISO/ASCII",
%%% keywords = "file name, filename, path name, pathname,
%%% discretionary, discretionaries",
%%% supported = "yes",
%%% docstring = {Computer filenames, host names, and e-mail
%%% addresses tend to be long strings that
%%% cause line breaking problems for TeX.
%%% Sometimes rather long strings are
%%% encountered, such as:
%%%
%%% mighty-mouse-gw.scrc.symbolics.com
%%%
%%% This file defines a macro, \path|...|,
%%% similar to LaTeX's \verb|...| macro, that
%%% sets the text in the typewriter font,
%%% allowing hyphen-less line breaks at
%%% punctuation characters.
%%%
%%% The default set of punctuation characters is
%%% defined as
%%%
%%% \discretionaries |~!@$%^&*()_+`-=#{"}[]:;'<>,.?\/|
%%%
%%% However, you can change it as needed, for
%%% example
%%%
%%% \discretionaries +@%!.+
%%%
%%% would assign to it the set @ % ! . which
%%% commonly occur in electronic mail addresses.
%%%
%%% The delimiter characters surrounding the
%%% arguments to \discretionaries and \path
%%% will normally be a punctuation character not
%%% found in the argument, and not otherwise
%%% significant to TeX. In particular, backslash
%%% cannot be used as a delimiter. In the rare
%%% event that this is required, set
%%%
%%% \specialpathdelimiterstrue
%%%
%%% This practice is not recommended, because TeX
%%% then runs about four times slower while it is
%%% typesetting \path\...\ requests.
%%% \specialpathdelimitersfalse is the normal
%%% setting.
%%%
%%% This file may be used in Plain TeX or AmSTeX
%%% by
%%%
%%% \input path.sty
%%%
%%% and in LaTeX by
%%%
%%% \usepackage {path}
%%%
%%% The checksum field above, if present, contains
%%% a CRC-16 checksum as the first value, followed
%%% by the equivalent of the standard UNIX wc (word
%%% count) utility output of lines, words, and
%%% characters. This is produced by Robert
%%% Solovay's checksum utility.
%%% }
%%% }
%%% ====================================================================
% ======================================================================
%
% The \path Macro
%
% An early prototype of this code which was developed by Nelson H. F.
% Beebe <beebe@math.utah.edu> used a recursive macro to peel off one
% character at a time, then with a nest of \ifx statements, test for
% each punctuation character, and if one is found, insert discretionary
% linebreaks in the form of \- or \penalty0. While this usually works,
% it is not entirely satisfactory, because the nested \ifx statements
% are ugly, and the recursion can exhaust TeX's macro stack for
% arguments longer than about 30 characters.
%
% A second version by NHFB built upon the ideas used by the LaTeX
% \verb|...| macro; this was mostly successful, but was flawed by its
% inability to handle at least the three characters ^ [ ], by loss of
% use of @ for naming internal private macros, and by its inability to
% allow the set of characters at which breaks are permissible.
%
% The problem was then passed off to Philip Taylor, who wrote this third
% version which fully solves the problem. Phil therefore gets the
% author credit in the file header above. [Gee, thanks ! ** Phil]
%
% Revision history (reverse time order):
%
% 3.05 [7-Apr-2011]
% Summary: Use \path instead of \ATcode to save the catcode of @.
% Expand \pathafterhook after \path's work is done.
%
% 3.04 [incorporated as part of Eplain]
%
% 3.03b [22-Jul-1997]
% Summary: No code changes. An out-of-date example removed, the syntax
% for LaTeX2e changed to "\usepackage {path}", and the "checksum"
% comments modified to indicate that the checksum is not necessarily
% present. The initial opening brace re-positioned to align
% with the matching closing brace, and the inner closing brace
% re-positioned to align with the inner opening brace. A check made
% to ensure that no <tab> characters are present.
%
% 3.03a [22-Jul-1997]
% Summary: No code changes from V3.03; e-mail addresses, telephone numbers,
% etc. amended to reflect current situation. Checksum removed.
%
% 3.03 [03-Dec-1991]
% Problem: A \path|...| entry in a LaTeX index is set with an
% preceding blank line.
% Solution: Add \leavevmode before \hbox{}; without it, an extra blank
% line gets typeset before every invocation of \path in a
% LaTeX theindex environment.
% Diagnosis: To avoid hyphenation, the expansion of \path starts with
% an \hbox{} (c.f. the TeXbook, p. 454); LaTeX indices are
% basically set in vertical mode, with each index entry a
% paragraph in its own right; when an \hbox {} is
% encountered in vmode, it is typeset in vmode, and TeX
% continues; the first real character is encountered, and
% TeX enters unrestricted horizontal mode. The \hbox {} and
% the first character are therefore on separate lines,
% separated by \baselineskip.
%
% 3.02 [23-Oct-1991 13:45:12]
% First released version.
% ======================================================================
\immediate \write 16 {This is path.sty, Version 3.05 <7-Apr-2011>}
%%% The use of `\path' as a temporary control sequence is a kludge, but
%%% it's a reasonably simple way to accomplish making @ a letter (to
%%% provide ``concealed'' control sequences) without overwriting something
%%% (without an `@' in its name) that might already be defined.
\edef \path {\the \catcode `\@}%
\catcode `\@ = 11
\let \oldc@tcode = \path
%%% Make commercial-at a letter to provide concealed control sequences
\catcode `\@ = 11
%%% and then declare two \count variables with concealed names
\newcount \c@tcode
\newcount \c@unter
%%% and a boolean variable with an open name, to specify the nature of
%%% the delimiters which will be associated with the \path command
\newif \ifspecialpathdelimiters
%%% If desired, you can define \pathafterhook to take
\let \pathafterhook = \relax
%%% We need to define control sequences which expand to both
%%% active and passive spaces ...
\begingroup
\catcode `\ = 10
\gdef \passivesp@ce { }
\catcode `\ = 13\relax%
\gdef\activesp@ce{ }%
\endgroup
%%% \discretionaries will define a macro \discr@ti@n@ri@s which will
%%% make every character between the first and final <delim> a
%%% discretionary breakpoint.
\def \discretionaries %%% <delim> <chars> <delim>
% start a group (ended in \discr@ti@naries ),
% make every character (apart from space) active,
% then transfer control to \discr@tionaries ...
{\begingroup
\c@tcodes = 13
\discr@tionaries
}
%%% \discr@tionaries will receive as parameter the initial <delim>
%%% which will delimit the set of discretionaries; this <delim>
%%% will be active.
\def \discr@tionaries #1%%% <delim>
% knowing the initial <delim>, define \discr@ti@naries with a
% delimited parameter structure, the final delimiter being
% the second instance of <delim>
{\def \discr@ti@naries ##1#1%%% <chars> <delim>
% \discr@ti@naries will receive as parameter the set of
% characters which are to be made discretionaries; it ends the
% group and then defines \discr@ti@n@ries, a tail-recursive
% macro, which will quietly process each of the
% discretionaries in turn ...
{\endgroup
\def \discr@ti@n@ries ####1%%% <char> or <delim>
% by checking to see if it has reached the end of the
% list, i.e. comparing its parameter with the known final
% <delim> ...
{\if \noexpand ####1\noexpand #1%
% if they match, there is no more to do ...
\let \n@xt = \relax
\else
% otherwise the character becomes active and is
% defined as a discretionary with the three texts
% <self> <empty> <self>, thus suppressing true
% hyphenation; the macro then prepares to process
% the next character.
\catcode `####1 = 13
\def ####1{\discretionary
{\char `####1}{}{\char `####1}}%
\let \n@xt = \discr@ti@n@ries
\fi
% here either tail recursion occurs, if there are more
% characters to process, or tail recursion ceases if all
% have been exhausted
\n@xt
}%
% of course, none of this must take place during the \stress
% {call} of \discretionaries; execution is deferred until
% another macro such as \path calls the concealed action
% macro \discr@ti@n@ri@s; we therefore define this macro to
% have the desired effect.
\def \discr@ti@n@ri@s {\discr@ti@n@ries ##1#1}%
}%
% and finally invoke \discr@ti@naries to process the set of
% discretionary characters; it will take everything up to the
% second instance of <delim> as its parameter (and therefore as the
% set of characters to be processed).
\discr@ti@naries
}
%%% \path, which is the user interface to \p@th, first checks
%%% to see whether \specialpathdelimiters is <true> or <false>;
%%% if <true>, it needs to take special action to ensure that
%%% \stress {all} characters (apart from <space>) are acceptable
%%% as delimiters; this is very time-consuming, and should be
%%% avoided if at all possible. It also defines \endp@th, to
%%% close the appropriate number of groups, and finally transfers
%%% control to \p@th
\def \path
{\ifspecialpathdelimiters
\begingroup
\c@tcodes = 12
\def \endp@th {\endgroup \endgroup \pathafterhook}%
\else
\def \endp@th {\endgroup \pathafterhook}%
\fi
\p@th
}
%%% \p@th, which has essentially the same syntax as \discretionaries,
%%% expects to be followed by a <delim>, a <path>, and a second instance
%%% of <delim>; it will typeset <path> in the \tt font with hyphenation
%%% inhibited --- breaks (but not true hyphenation) are allowed at any
%%% or all of the special characters which have
%%% previously been declared as \discretionaries.
\def \p@th #1%%% <delim>
% it starts by opening a group (ended in \p@@th) ...
% switches to \tt, and inhibits hyphenation;
% allows breaks at \discretionaries; saves the
% catcode of the initial <delim>, because if it has also been
% declared within \discretionaries, the initial and final <delim>
% won't match (which would be a disaster); \c@tcode is overloaded,
% but there is no conflict that I can detect ...
% invokes \discr@ti@n@ri@s to render active the set of special
% characters which have previously been declared as
% \discretionaries; each of these characters will expand to a real
% \discretionary, with replacement texts <self> <null> <self>; and
% re-instates the catcode of the initial <delim>.
{\begingroup
\tt
\c@tcode = \catcode `#1
\discr@ti@n@ri@s
\catcode `\ = \active
\expandafter \edef \activesp@ce {\passivesp@ce \hbox {}}%
\catcode `#1 = \c@tcode
% it next defines an inner macro \p@@th with delimited parameter
% structure, the final delimiter being the same as the initial
% delimiter which it has itself received as #1.
\def \p@@th ##1#1% <chars> <delim>
% Within \p@@th,
% permissible breakpoints are specified,
% the path is typeset,
% and the group(s) ended.
{\leavevmode \hbox {}##1%
\endp@th
}%
\p@@th
}
%%% \c@tcodes expects to be followed by the r-h-s of a numeric
%%% assignment optionally including the assignment operator; it saves
%%% the value of the r-h-s in \c@tcode, and invokes \c@tc@des.
\def \c@tcodes {\afterassignment \c@tc@des \c@tcode}
%%% \c@tc@des uses the value saved in \c@tcode, and assigns it to the
%%% \catcode of all characters with the single exception of <space>,
%%% which retains its normal catcode of 10; on exit, every single
%%% character apart from <space> will have the catcode which followed
%%% \c@tcodes. The code is optimised to avoid unnecessary usage of
%%% save-stack space.
\def \c@tc@des
{\c@unter = 0
\loop
\ifnum \catcode \c@unter = \c@tcode
\else
\catcode \c@unter = \c@tcode
\fi
\ifnum \c@unter < 255
\advance \c@unter by 1
\repeat
\catcode `\ = 10
}
%%% We restore the original catcode of commercial-at
\catcode `\@ = \oldc@tcode
%%% Define a default set of discretionary break characters
%%% to include all punctuation characters except vertical
%%% bar
\discretionaries |~!@$%^&*()_+`-=#{}[]:";'<>,.?\/|
\endinput