path: root/Master/texmf-dist/doc/latex/cweb-latex/src/keyvald.dtx

%% $ITI: keyvald.dtx,v 1.2 1995/08/25 19:00:31 schrod Exp $
%%------------------------------------------------------------
%% (history at end)
%
% \iffalse
%% File: keyvald.dtx; changed version of
%% File: keyval.dtx Copyright (C) 1993-1994 David Carlisle
%
%<*dtx>
          \ProvidesFile{keyvald.dtx}
%</dtx>
%<*!plain>
%<package&!plain>\NeedsTeXFormat{LaTeX2e}
%<package&!plain>\ProvidesPackage{keyvald}
%<driver>        \ProvidesFile{keyvald.drv}
% \fi
%                \ProvidesFile{keyvald.dtx}
                 [1994/08/23 v1.08.1 key=value parser (DPC) w/ defaults (js)]
%
% \iffalse
%</!plain>
%<*driver>
\documentclass{ltxdoc}
\usepackage{keyvald}
\begin{document}
 \DocInput{keyvald.dtx}
\end{document}
%</driver>
% \fi
%
% \GetFileInfo{keyvald.dtx}
% \title{The \textsf{keyvald} package\thanks{This file
%        has version number \fileversion, last
%        revised \filedate.}}
% \author{David Carlisle\\carlisle@cs.man.ac.uk
%       \and
%       changed by\\Joachim Schrod\\
%       \texttt{<schrod@iti.informatik.th-darmstadt.de>}
%       }
% \date{\filedate}
% \maketitle
%
% \begin{abstract}
%  A \LaTeX\ package implementing a system allowing the setting
%  of parameters (or `named arguments' with a
%  \meta{key}${}={}$\meta{value} syntax.
%
%  Eg: |\foo[height=3in, shadow = true ]{bar}|
% \end{abstract}
%
% \CheckSum{110}
%
% \changes{v1.03}
%         {1993/10/13}{Initial version}
% \changes{v1.04}{1993/11/15}
%         {Upgrade after comments from Timothy van Zandt}
% \changes{v1.05}{1993/11/17}
%         {Further small improvements}
% \changes{v1.06}{1994/02/01}
%         {Update to LaTeX2e}
% \changes{v1.07}{1994/03/15}
%         {New style ltxdoc}
% \changes{v1.08}{1994/09/12}
%         {Improve docstrip handling}
% \changes{v1.08.1}{1995/08/23}
%         {Default keys}
%
%
% This package implements a system of defining and using sets of
% parameters, which are set using the syntax \meta{key}=\meta{value}.
%
% For each keyword in such a set, there exists a function which is
% called whenever the parameter appears in a parameter list. For
% instance if the set |dpc| is to have the keyword |scale| then I
% would define.\\
% | \define@key{dpc}{scale}{scale ({\tt\string#1})\\}|\\
% The first argument of |\define@key| is the  set of keywords being
% used, the second is the keyword, and the third is the function to
% call. This function will be given as |#1| the \meta{value} specified
% by the user.
%
% Normally it is an error to omit the `=\meta{value}' however if an
% optional \meta{value} is supplied when the keyword is defined, then
% just the keyword need be supplied.\\
% |\define@key{dpc}{clip}[true]{...}|\\
% For `|clip|' you can go `|clip = true|' or `|clip = false|' or
% just `|clip|', which is the same as `|clip = true|'
%
% To use these keywords, just call `|\setkeys|' with a comma
% separated list of settings, each of the form
% \meta{key}=\meta{value}, or just \meta{key}. Any white space around
% the `|=|' and `|,|' is ignored.
%
% As the \meta{key} is passed as a macro argument, if it consists
% entirely of a |{ }| group, the outer  braces are stripped off. Thus
% |,key=foo,| and |key=,{foo},| are equivalent. This fact enables one to
% `hide' any commas or equals signs that must appear in the value. i.e.\
% in |foo={1,2,3},bar=4|, |foo| gets the value |1,2,3|, the comma after
% |1| does not terminate the keyval pair, as it is `hidden' by the
% braces.
%
% Empty entries, with nothing between the commas, are silently ignored.
% This means that it is not an error to have a comma after the last
% term, or before the first.
%
% \section{Example}
%
% We may extend the examples above to give  a `fake' graphics
% inclusion macro, with a syntax similar to that used in the psfig
% macros.
%
% \makeatletter
% \def\dpcgraphics{\@ifnextchar[\@dpcgraphics{\@dpcgraphics[]}}
%
% |\dpcgraphics| has one optional argument which is passed through
% |\setkeys|, and one mandatory argument, the filename. It actually
% just typesets its arguments, for demonstration.
%
% \def\@dpcgraphics[#1]#2{{\setkeys{dpc}{#1}INPUT: #2}}%
%
% \define@key{dpc}{scale}{scale ({\tt\string#1\relax})\\}
% \define@key{dpc}{height}{height ({\tt#1})\\}
% \define@key{dpc}{width}{width ({\tt#1})\\}
% \define@key{dpc}{bb}{bounding box ({\tt#1})\\}
% \define@key{dpc}{clip}[true]{clip ({\tt\string#1\relax})\\}
% \makeatother
%
% The declared keys are: |scale|, |height|, |width|, |bb|,
% and |clip|. Except for the last, they must all be given a value if
% used.
%
% Note how in the following, any white space arround |=| or |,| is
% ignored, as are the `empty' arguments caused by extra commas. Note
% also that each macro receives {\em exactly\/} the tokens that you
% specify as arguments, no premature expansion is done.
%
% \begin{verbatim}
% \def\dpcgraphics{\@ifnextchar[\@dpcgraphics{\@dpcgraphics[]}}
% \def\@dpcgraphics[#1]#2{{\setkeys{dpc}{#1}INPUT: #2}}
%
% \define@key{dpc}{scale}{scale ({\tt\string#1\relax})\\}
% \define@key{dpc}{clip}[true]{clip ({\tt\string#1\relax})\\}
% \end{verbatim}
%
% \begin{minipage}{.4\textwidth}
% \begin{verbatim}
% \def\scalemacro{9}
% \dpcgraphics
% [ height =4in, ,
%   width = 3in,
%   scale = \scalemacro,
%   bb = 20 20 300 400 ,
%   clip,
%  ]{aaa}
% \end{verbatim}
% \end{minipage}
% \hfill
% \begin{minipage}{.4\textwidth}
% \def\scalemacro{9}
%\dpcgraphics
% [ height =4in, ,
%   width = 3in,
%   scale = \scalemacro ,
%   bb = 20 20 300 400 ,
%   clip ,
%  ]{aaa}
% \end{minipage}
%
%
% \section{The Internal Interface}
% A declaration of the form:\\
% |\define@key{family}{key}{...}|\\
% Defines a macro |\KV@prefix@key| with one argument. When used in a
% keyval list, the macro receives the value as its argument.
%
% A declaration of the form:\\
% |\define@key{family}{key}[default]{...}|\\
% Defines a macro |\KV@family@key| as above, however it also defines the
% macro |\KV@family@key@default| as a macro with no arguments, and
% definition\\
%  |\KV@family@key{default}|.
%
% Thus if macros are defined using |\define@key|, the use of a key with
% no value \ldots|,foo,|\ldots\ is always equivalent to the use of the
% key with some value, \ldots|,foo=default,|\ldots. However a package
% writer may wish that the `default' behaviour for some key is not
% directly equivalent to using that key with a value. (In particular, as
% pointed out to me by Timothy Van Zandt, you may wish to omit error
% checking on the default value as you know it is correct.) In these
% cases one simply needs to define the two macros
% |\KV@|\meta{family}|@key| and |\KV@|\meta{family}|@key@default|
% directly using |\def| (or |\newcommand|). I do not supply a user
% interface for this type of definition, but it is supported in the
% sense that I will try to ensure that any future upgrades of this
% package do not break styles making use of these `low level'
% definitions.
%
% \StopEventually{}
%
% \section{The Macros}
%
% From version~1.05, all `internal' macros associated to keys have names
% of the form:\\
% |\KV@|\meta{family}|@|\meta{key} or
% |\KV@|\meta{family}|@|\meta{key}|@|\meta{default}
%
%    \begin{macrocode}
%<*package>
%    \end{macrocode}
%
% \begin{macro}{\setkeys}
% The top level macro. |#2| should be a comma separated values of the
% form  \meta{key} |=| \meta{value} or just simply \meta{key}.
% The macro associated with this key in the `family' |#1| is called with
% argument \meta{value}. The second form is only allowed if the key was
% declared with a default value.
%    \begin{macrocode}
\def\setkeys#1#2{%
%    \end{macrocode}
%  Save the `family' for later. Then begin acting on the comma
%  separated list.
%    \begin{macrocode}
  \def\KV@prefix{KV@#1@}%
  \KV@do#2,\relax,}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@do}
% Iterate down the list of comma separated argument pairs.
%    \begin{macrocode}
\def\KV@do#1,{%
 \ifx\relax#1\empty\else
  \KV@split#1==\relax
  \expandafter\KV@do\fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@split}
% Split up the keyword and value, and call the appropriate command.
% This macro was slightly reorganised for version 1.04, after some
% suggestions from Timothy Van Zandt.
%    \begin{macrocode}
\def\KV@split#1=#2=#3\relax{%
  \KV@@sp@def\KV@key{#1}%
  \ifx\KV@key\@empty\else
    \expandafter\let\expandafter\@tempc
      \csname\KV@prefix\KV@key\endcsname
    \ifx \@tempc\relax
      \expandafter\let \expandafter\@tempc
        \csname\KV@prefix*\endcsname
      \def\@tempa{*}%
    \else
      \let\@tempa\KV@key
    \fi
    \ifx\@tempc\relax
      \KV@err{\KV@key\space undefined}%
    \else
      \ifx\@empty#3\@empty
        \KV@default
      \else
        \KV@@sp@def\@tempb{#2}%
        \expandafter\@tempc\expandafter{\@tempb}\relax
      \fi
    \fi
  \fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@default}
% Run the default code, or raise an error.
%    \begin{macrocode}
\def\KV@default{%
  \expandafter\let\expandafter\@tempb
    \csname\KV@prefix\@tempa @default\endcsname
  \ifx\@tempb\relax
    \KV@err{No value specified for \KV@key}%
  \else
    \@tempb\relax
  \fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@err}
% Error messages.
%    \begin{macrocode}
\def\KV@err#1{\PackageError{keyvald}{#1}{}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@@sp@def}
% \begin{macro}{\KV@@sp@b}
% \begin{macro}{\KV@@sp@c}
% |\KV@@sp@def|\meta{cmd}\meta{token list} is like |\def|, except that
% a space token at the beginning or end of \meta{token list} is
% removed before making the assignment. \meta{token list} may not
% contain the token |\@nil|, unless it is within a brace group.
% The names of these commands were changed at version~1.05 to ensure
% that they do not clash with `internal' macros in a key family `sp'.
%
% The following three lines are equivalent to\\
% |\def\KV@@sp@def#1#2{\KV@@sp@b#2\@nil\@nil~\@nil\relax#1}|\\
% Where |~| is an explicit space token.
%    \begin{macrocode}
\def\@tempa#1{%
\def\KV@@sp@def##1##2{\KV@@sp@b##2\@nil\@nil#1\@nil\relax##1}}
\@tempa{ }
\def\KV@@sp@b#1#2 \@nil{\KV@@sp@c#1#2}
\def\KV@@sp@c#1\@nil#2\relax#3{\def#3{#1}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\define@key}
% Define the command associated to the key |#2| in the family |#1|.
% First looks for a default argument (the default value for the
% key)
%    \begin{macrocode}
\def\define@key#1#2{%
  \@ifnextchar[{\KV@def{#1}{#2}}{\@namedef{KV@#1@#2}####1}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\KV@def}
% Make the definitions of the command, and the default value.
%    \begin{macrocode}
\def\KV@def#1#2[#3]{%
  \@namedef{KV@#1@#2@default\expandafter}\expandafter
    {\csname KV@#1@#2\endcsname{#3}}%
  \@namedef{KV@#1@#2}##1}
%    \end{macrocode}
% \end{macro}
%
%    \begin{macrocode}
%</package>
%    \end{macrocode}
% \Finale
%
\endinput

%------------------------------------------------------------
%
% $ITIlog: keyvald.dtx,v $
% Revision 1.2  1995/08/25  19:00:31  schrod
%     Add enhanced version of keyval package, with ability to specify
% default action for unknown keyword options.
%