% lin.sty - LaTeX2e functions for automating Linnaean taxa
%
% 0.1 Peter Flynn, 2002-04-28, with help from users on c.t.t.
%
% WARNING: BROKEN. THIS IS A PROOF-OF-CONCEPT NOT A PRODUCT
%
% Define names in the preamble with the command
%
%      \lin{shortname}{Genus}{species}
%
% This creates \shortname as a command, which typesets the full
% name the first time and the short form on subsequent uses. 
% Names are set using \emph, so they are italic in roman text
% and roman in italic text. The command is reset automatically
% when the chapter changes (in document classes where \chapter
% is usable), when the section changes (in other classes), and
% after the abstract, so that it again produces the full name
% on next use and the abbreviated form subsequently.
%
% BUGS
%
% Currently the first name used after a section/chapter change
% causes the context signal to be set false, so other names are
% wrongly printed in short form on first reference that section
% or chapter. The context signal needs to be on a per-name basis,
% but that's going to be pretty expensive in namespace.
%
% TO DO
% 
% Tidy this up into a proper package of .dtx / .ins files
%
% Add a 4th [optional] argument to allow subspecies, varieties,
% or 
%
% Make it force full format when used in the argument of titles
% like \title, \chapter, and \section (tricky: command argument
% in LaTeX are not object-aware)
%
% Force detection of already-defined Genus with the same initial,
% and shift the capital abbreviation to two letters (cap+lc).
% Presumably the rule means a third Genus would mean a shift to
% three letters...
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
\newcommand{\lin}[3]{%
% define the new command inside a command which will do the resetting
% needed after abstracts, chapters, and sections
	\expandafter\def\csname LIN@reset@#1\endcsname{%
% the next line defines the command
		\expandafter\def\csname #1\endcsname{%
% which immediately expands to the full name and records the context
% in terms of chapter or section number
			\emph{#2\ #3}\LIN@setcontext%
% and then redefines itself to do several things
			\expandafter\def\csname #1\endcsname{%
% a) to test the context to see if chapter or section has changed 
				\LIN@testcontext
% b) if it *has*, we want the full Monty again
				\ifLIN@newcontext
%    (i) perform a reset of itself
					\csname LIN@reset@#1\endcsname
%    (ii) set the context to "unchanged"
					\LIN@newcontextfalse
%    (iii) and finally call itself to typeset the full name
					\csname #1\endcsname
% c) if the context has *not* changed
				\else
%    just typeset the short version, stripping Genus to an initial
					\emph{\LIN@init#2\sentinel.~#3}%
				\fi}}}%
% having defined a command to define all this, now actually execute it
	\csname LIN@reset@#1\endcsname}
%
% UTILITIES
%
% Routine extract first character of a string (used for Genus)
% This needs generalising with an extra argument for the length of
% the initial substring to extract (or maybe just three versions
% of the same command eg \LIN@initi, \LIN@initii, and \LIN@initiii
% to extract 1, 2, or 3 characters).
\def\LIN@init#1#2\sentinel{#1}
%
% Define a toggle to flag if the context (abstract, chapter, section)
% has changed or not
\newif\ifLIN@newcontext
% Memorize the existing \endabstract (check if this can be relied upon)
\let\LIN@endabstract\endabstract
% Redefine \endabstract to force the context flag to signal "changed"
\gdef\endabstract{\LIN@endabstract\LIN@newcontexttrue}
% Define a counter to hold the current chapter or section number
\newcounter{LIN@context}
% Define the context-testing routine twice, once for articles, which
% use \section as their top-level division, and once for books and
% reports which use \chapter
\@ifundefined{thechapter}% 
	{\newcommand{\LIN@testcontext}%
% If the context counter (ie existing value) is the same as the value
% of the current section, set the flag to false (no change in section)
		{\ifnum\c@LIN@context=\c@section
			\LIN@newcontextfalse
% otherwise set it to true
		 \else
			\LIN@newcontexttrue
% set the counter to the current (ie new) section value
		 \fi\LIN@setcontext}%
% and define the context-setter to use the section counter
	\newcommand{\LIN@setcontext}{\c@LIN@context=\c@section}}%
% Same structure exactly for chapters
	{\newcommand{\LIN@testcontext}%
		{\ifnum\c@LIN@context=\c@chapter
			\LIN@newcontextfalse
		 \else
			\LIN@newcontexttrue
		 \fi\LIN@setcontext}
	\newcommand{\LIN@setcontext}{\c@LIN@context=\c@chapter}}
%
% Details see http://www.wikipedia.com/wiki/Linnaean+taxonomy
%
\endinput
%
% Sample instance
%
\documentclass{article}
\usepackage{lin}
\usepackage[latin1]{inputenc}
\lin{daisy}{Ranunculus}{ficaria}
\lin{oak}{Quercus}{robur}
\begin{document}
\title{Linnæan taxa}
\author{Peter Flynn}
\date{2002-04-29}
\maketitle
\begin{abstract}
This is a story about the \daisy\ and the \oak.
\end{abstract}
\section{Introduction}
Once upon a time there was a \daisy\ growing at the foot of the
old \oak. Every time it rained, the \oak's leaves sheltered the
little \daisy.
\section{Conclusion}
When the \daisy\ grew up and the \oak\ got older and wiser they 
gave a wild party.
\end{document}