% $Id: xifthen.tex,v 1.1.1.1 2006/03/25 01:24:34 noirel Exp $
\documentclass{article}

\usepackage{etex}
\usepackage{xifthen}
\usepackage[ascii]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[warn]{textcomp}
\usepackage{fourier}
  \renewcommand*{\sfdefault}{lmss}
  \renewcommand*{\ttdefault}{lmtt}
  \renewcommand*{\textcompsubstdefault}{lmr}
\usepackage{microtype}
\usepackage{typetex}
\usepackage[babel]{csquotes}
\usepackage[british]{babel}

\makeatletter
\newenvironment*{texdescription}{%
  \list{}{%
    \labelwidth\z@
    \itemindent-\leftmargin
    \itemsep = 0pt
    \def \makelabel ##1{\hspace{\labelsep}\normalfont\tex{##1}}%
  }%
}{%
  \endlist
}
\makeatother

\newcommand*{\pack}{\textsf}
\newcommand*{\true}{\emph{true}}
\newcommand*{\false}{\emph{false}}

\newtest \sillytest [2]{%
  \cnttest{(#1)*(#2)}>{100}%
  \AND
  \cnttest{((#1)+(#2))*2}<{60}%
}

\texsetup {%
  meta-left-char = {\textlangle},
  meta-right-char = {\textrangle}
}

\title  {The \pack{xifthen} package}
\author {Josselin Noirel}

\begin{document}

\maketitle

\begin{abstract}
  This package implements new commands to go within the first argument of
  \cmd{ifthenelse} to test whether a string is void or not, if a command
  is defined or equivalent to another.  It includes also the possibility
  to make use of the complex expressions introduced by the
  package~\pack{calc}, together with the ability of defining new commands
  to handle complex tests.  This package requires the \eTeX{} features.
\end{abstract}

\section{General syntax}

The general syntax is inherited of that of the package~\pack{ifthen}:
%
\begin{displaytex}
  \cmdsyntax[3]{ifthenelse}{test expression}{true code}{false code}
\end{displaytex}
%
Evaluates the \meta{test expression} and executes \meta{true code} if the
test turns out to be true and \meta{false code} otherwise.  \pack{ifthen}
provides the following tests:
%
\begin{texdescription}
\item [\meta{value $1$} = \meta{value $2$}]
\item [\meta{value $1$} < \meta{value $2$}]
\item [\meta{value $1$} > \meta{value $2$}]
      Simple tests on integer comparisons.

\item [{\cmdsyntax[1]{isodd}{number}}]
      Is \meta{number} odd?

\item [\cmd{isundefined}\meta{command}]
      Id \meta{command} undefined?

\item [{\cmdsyntax[2]{equal}{string $1$}{string $2$}}]
      Are \meta{string $1$} and \meta{string $2$} equivalent (after
      expansion)?

\item [{\cmdsyntax[1]{boolean}{boolean}}]
      Does the boolean \meta{boolean} hold the value \true{} or \false{}?

\item [{\cmd[1]{lengthtest}{\meta{dimen $1$} = \meta{dimen $2$}}}]
\item [{\cmd[1]{lengthtest}{\meta{dimen $1$} < \meta{dimen $2$}}}]
\item [{\cmd[1]{lengthtest}{\meta{dimen $1$} > \meta{dimen $2$}}}]
      Simple dimension comparisons.

\item [\cmd{(}\dots\cmd{)}]
      Parenthesis.

\item [\cmd{AND}]
\item [\cmd{OR}]
\item [\cmd{NOT}]
      Conjunction, disjunction, negation.
\end{texdescription}

\section{New tests}

\begin{displaytex}
  \cmdsyntax[1]{isnamedefined}{command name}
\end{displaytex}
%
Returns \true{} if the command \cmd{\meta{command name}} is defined.

\begin{displaytex}
  \cmdsyntax[1]{isempty}{content}
\end{displaytex}
%
Returns \true{} is \meta{content} is empty (in the sense used by
\pack{ifmtarg} which is used internally).  It is essentially equivalent to
\tex{\cmd[2]{equal}{\meta{content}}{}} except that the argument of
\cmd{isempty} isn't expanded and therefore isn't affected by fragile
commands.

\begin{displaytex}
  \cmdsyntax[2]{isequivalentto}{command~$1$}{command~$2$}
\end{displaytex}
%
Corresponds to the \cmd{ifx} test: it returns \true{} when the two
commands are exactly equivalent (same definition, same number of
arguments, etc., otherwise \false{} is returned.

\begin{displaytex}
  \cmd{cnttest}\marg{counter expression $1$}\meta{comparison}%
               \marg{counter expression $2$}
\end{displaytex}
%
Compares the two counter expressions (having the usual syntax of the
package \pack{calc}) and returns the value of the test.  The comparison
can be one of the following characters \tex{<}, \tex{>},~and~\tex{=}.

\begin{displaytex}
  \cmd{dimtest}\marg{dimen expression $1$}\meta{comparison}%
               \marg{dimen expression $2$}
\end{displaytex}
%
Compares the two dimension expressions (having the usual syntax of the
package \pack{calc}) and returns the value of the test.  The comparison
can be one of the following characters \tex{<}, \tex{>},~and~\tex{=}.

\section{Defining new complex test commands}

\begin{displaytex}
  \cmdsyntax[3]{newtest}{command}[$n$]{test expression}
\end{displaytex}
%
Defines a command named \meta{command} taking $n$~arguments (no optional
argument is allowed) consisting of the test as specified by \meta{test
  expression} that can be used in the argument of \cmd{ifthenelse}.  For
instance, if we want to test whether a rectangle having dimensions
$l$~and~$L$ meets the two following conditions: $S = l \times L > 100$
and~$P = 2 (l +\nobreak L) < 60$:
%
\begin{displaytex}
\cmd{newtest}\{\cmd{sillytest}\}[2]\{\%\newline
\ \ \cmd{cnttest}\{(\#1)*(\#2)\}>\{100\}\%\newline
\ \ \cmd{AND}\newline
\ \ \cmd{cnttest}\{((\#1)+(\#2))*2\}<\{60\}\%\newline
\}
\end{displaytex}
%
Then \tex{\cmd{ifthenelse}\{\cmd{sillytest}\{14\}\{7\}\}\{TRUE\}\{FALSE\}}
returns \ifthenelse{\sillytest{14}{7}}{TRUE}{FALSE} because $14\times 7 =
98$ and $2\times (14 +\nobreak 7) = 42$, while
\tex{\cmd{ifthenelse}\{\cmd{sillytest}\{11\}\{11\}\}\{TRUE\}\allowbreak
  \{FALSE\}} returns \ifthenelse{\sillytest{11}{11}}{TRUE}{FALSE} because
$11 \times 11 = 121$ and $2\times (11 +\nobreak 11) = 44$.

\end{document}