Hi Maurice,
The 'key' to the keyval functionality in ConTeXt are two macros called
\getparameters and \processaction.
Here is a 'quickstart', assuming you want to define \myzigzag:
%
\unprotect % enable exclamations in macro names
\def\myzigzag#1[#2]{%
% the #1 makes sure we allow a space before the bracket
%
\getparameters[ZZ][Dir=,Linewidth=1pt,Color=Red,Width=3em,#2]
%
% Now you have a set of new macros that all start with ZZ.
% At least there are \ZZDir,\ZZLinewidth, \ZZColor and \ZZWidth
% (these have default values) but possibly others as well,
% depending on user input.
%
% Here's a usage example:
%
\edef\mywidth{\ZZWidth}%
%
% If you want to use keyword values, then you also need
% to use \processaction.
%
% Say you want "Dir" to be mandatory and that it
% accepts 4 directional keywords, as well as a direct
% angle specification.
%
% I've used all mixed case keywords, because otherwise
% you might run into conflicts with the multilingual interface
%
\expandafter\processaction\expandafter[\ZZDir]
[Down =>\def\Dir{270},
Left =>\def\Dir{180},
Up =>\def\Dir{90},
Right =>\def\Dir{0},
\s!default =>\errorDir,
\s!unknown =>\checkDir{\ZZDir}]
%
% \s!default may be triggered because \ZZDir's expansion is
% empty unless the user supplied something.
%
% The first argument to \processaction has to be expanded,
% so you need the \expandafter's.q
}
% for completeness, here is an example definition of \checkDir and
% \errorDir:
\def\errorDir{%
\def\Dir{0}% error recovery
\message{Please supply "Dir" argument}%
}
\def\checkDir#1{%
\doifnumberelse {#1}
{\def\Dir{#1}}
{\message{Invalid "Dir" argument! (#1)}}
}
\protect % end of definitions
On Sat, 26 Jun 2004 11:51:14 +0200, Maurice wrote:
> Bonjour à tous,
>
> One thing is missing in context (or not documented in reference manual?)
> is a standard and easy way to build arbitrary parametrised high level
> macros.
>
--
groeten,
Taco
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