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%
% Copyright (C) 2021 Dennis Chen <proofprogram@gmail.com>
%
% This file may be distributed and/or modified under
% the conditions the LaTeX Project Public License (LPPL),
% either version 1.3 of this license or (at your option)
% any later version. The latest version of this license
% can be found in
%   http://www.latex-project.org/lppl.txt
% and version 1.3 or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
% \fi
%
% \iffalse
%<package>
%<package>\NeedsTeXFormat{LaTeX2e}
%<package>\ProvidesPackage{ifallfalse}[2021/07/22 v2.0.0 Compare string against set of other strings]

%<*driver>
\documentclass{ltxdoc}
\usepackage{ifallfalse}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
    \DocInput{ifallfalse.dtx}
    \PrintIndex
\end{document}
%</driver>
% \fi
%
% \changes{v2.0.0}{2021/07/22}{Add comments after lines in allfalse to prevent extra spacing from popping up}
% \changes{v1.0.1}{2021/07/12}{Fix errant references to allfalse environment and add limitations}
% \changes{v1.0.0}{2021/07/01}{Initial version}
%
% \GetFileInfo{ifallfalse.sty}
%
% \title{\textsf{ifallfalse} -- Compare string against set of strings}
% \author{Dennis Chen \\ proofprogram@gmail.com}
% \changes{v2.0.0}{2021/07/22}{Remove errant `v' in date}
% \date{\fileversion, \filedate\thanks{\url{https://github.com/chennisden/ifallfalse}}}
%
% \maketitle
%
% \begin{abstract}
% The \textsf{ifallfalse} package is a package that allows you to check whether a string is contained within another set of strings, and perform an action if it is not.
% \end{abstract}
%
% \section{Usage}
%
% The package provides an \textsf{allfalse} environment and a macro |\orcheck| to be used inside the \textsf{allfalse} environment.
%
% \DescribeEnv{allfalse}
% To set up an allfalse environment, simply write
% \begin{verbatim}
%\begin{allfalse}{string}{true branch}{false branch}
%
%\end{allfalse}
% \end{verbatim}
% \textsf{string} will be compared to the set of strings (which we will declare via |\orcheck|), and if \textsf{string} does not match the set of strings, \textsf{false branch} will be executed. Otherwise, \textsf{true branch} will be executed.
%
% \DescribeMacro{\orcheck}
%
% To add strings to the set that \textsf{string} will be compared to, we must write |\orcheck{setstring}| inside the corresponding \textsf{allfalse} environment. Then, \textsf{action} will not execute if \textsf{string} matches \textsf{setstring} or any arguments of previous |\orcheck| declarations.
%
% If no |\orcheck| declarations exist, then \textsf{action} will always be executed.
%
% \subsection{Error Checking}
%
% The package checks whether the macro |\orcheck| is used inside an \textsf{allfalse} environment. If it is not, the package throws an error.
%
% \section{Example}
%
% Here is a simple example to demonstrate how \textsf{allfalse} is used.
%
% \changes{v2.0.0}{2021/07/22}{Change allfalse environment to match update}
% \changes{v2.0.0}{2021/07/22}{Use ifallfalse package in example}
% \begin{verbatim}
%\documentclass{minimal}
%\usepackage{ifallfalse}
%
%\begin{document}
%
%\begin{allfalse}{purple}{}{This color is not red, blue, or green!}
%    \orcheck{red}
%    \orcheck{blue}
%    \orcheck{green}
%\end{allfalse}
%
%\end{document}
% \end{verbatim}
%
% In this case, because \textsf{purple} does not match \textsf{red}, \textsf{blue}, or \textsf{green}, the false branch --- which is \textsf{This color is not red, blue, or green!} --- will execute at that location inside the document.
%
% \section{Implementation}
% 
% These are the implementation details of package \textsf{allfalse}. Because the package is so short, we can explain everything.
% 
% \changes{v2.0.0}{2021/07/22}{Create true and false branch}
% \begin{environment}{allfalse}
% When setting up allfalse, we locally define the |\comparedstring| macro with the first argument that the environment takes in. This is what will be compared against all the strings passed in through the |\orcheck| declarations inside the environment.
%
% Then, we define our body of logic (which we will be adding onto through |\orcheck|) to just initially consist of the action we would like to perform if |\comparedstring| matches none of the strings passed in through |\orcheck|.
%
% Finally, we execute our logicbody, which will change |\ifallfalse@branch| to be false if appropriate. Then, the appropriate action will be executed.
%    \begin{macrocode}
\newenvironment{allfalse}[3]
{%
    \newif\ifallfalse@branch\allfalse@branchtrue%
    \def\comparedstring{#1}%
    \def\trueaction{#2}%
    \def\falseaction{#3}%
    \def\logicbody{\protect\allfalse@branchfalse}%
}
{%
    \logicbody%
    \ifallfalse@branch
        \trueaction%
    \else
        \falseaction%
    \fi
}
%    \end{macrocode}
% \end{environment}
%
% \begin{macro}{\orcheck}
% We first save \textsf{allfalse} to a macro so we can use |\ifx| to compare the current environment name against it. If we can, then we add some following (somewhat convoluted) code to |\logicbody|. I will explain what each piece of it does, though not in the order the pieces of code appear.
% \begin{itemize}
% \item |\ifx\@currenvir\@allfalsename| evaluates to true if the current environment (whose name is saved to the macro |\@currenvir|) matches the name of |\@allfalsename|, or \textsf{allfalse}.
% \item If it evaluates to \textsf{false}, the package throws an error.
% \item The line |\pdfstrcmp{\comparedstring}{#1}=0| evaluates to true when put with |\ifnum| if the two arguments passed into |\pdfstrcmp| are equal, because |pdfstrcmp| compares their lexographical order and returns 0 if the two strings are lexographically equivalent.
% \item Thus, we can treat |\ifnum\pdfstrcmp{\comparedstring}{#1}=0| as an expression that evaluates to true if |\comparedstring| and |#1| match, and false otherwise.
% \item When all is said and done, the logic reduces to something of the form
% \begin{verbatim}
% \if\else
% \if\else
% \ldots \allfalse@branchfalse
% \fi\ldots \fi
% \end{verbatim}
% Logically, |\allfalse@branchfalse| will only execute if all the conditions are false; in other words, it will only execute if |\comparedstring| does not match any of the strings passed in via |\orcheck|. This is because each |\else| branch must execute. 
% \end{itemize}
%    \begin{macrocode}
\newcommand*\@allfalsename{allfalse}

\newcommand{\orcheck}[1]{
    \ifx\@currenvir\@allfalsename
        \protected@edef\logicbody{
            \ifnum\pdfstrcmp{\comparedstring}{#1}=0\else\logicbody\fi
        }
    \else
        \PackageError{ifallfalse}{
            \protect\orcheck\space should be nested within the allfalse environment
        }{}
    \fi
}
%    \end{macrocode}
% \end{macro}
%
% \section{Limitations}
%
% This package cannot be used in the \textsf{lualatex} engine.
%
% \Finale
\endinput
