gardener, Interface administrators, Administrators
3,893
edits
Changes
Jump to navigation
Jump to search
m
In LaTeX you define a new command < [[Inside ConTeXt]] | [[Commands with an optional argument with "newcommand":KeyVal arguments]] >
ConTeXtFor a command with two optional arguments, we use:<texcode>\def\MyCommand{\dodoubleempty\doMyCommand}</texcode>
There We then create the "private" macro (<tt>\doMacroName</tt> is perhaps a way to do the sametraditional ConTeXt name for these), with all the arguments defined as nonoptional. Otherwise, Default values for the arguments need to be handled somewhat more explicitly than with LaTeX; macros such as {{cmd|ifsecondargument}} are used to determine whether the key value method is preferredgiven argument was specified, see [[Define Commands]].as follows:
----<texcode> \def\doMyCommand[#1][#2]{#1Hello \ifsecondargument #2% \else World% \fi !}</texcode>
<i>The following Note that this makes both arguments optional -- something that is my understanding of how much more difficult to do thisin LaTeX ([http://www.tex.ac.uk/cgi-bin/texfaq2html?label=twooptarg but can be done]). It's currently untested; someone please test this and integrate This also means that we should reverse the order of arguments, since if the user specifies only one argument it with will be treated as the abovefirst argument. --[[User:Brooks|Brooks]]</i>
In ConTeXt(Also, the optional argument processing is handled as a two-step process. First, we write the command for the end-user as a wrapper command, which calls note that <tt>\dodoubleemptyMyCommand</tt> (from without the second argument ends up gobbling the following spaces, so we need to explicitly include one with "<tt>syst-gen.tex\ </tt>) to handle the arguments properly -- including the optional ones -- and then calls a "private" command that contains the internals of the macro. Note that this function call does not explicitly refer to the arguments at all.)
<texcode>\defMyCommand[\bf]\ %\MyCommand{\dodoubleempty[\doMyCommand}sc][Hans]</texcode>
We then create the "private" macro (<ttcontext>\doMacroName</tt> is the traditional ConTeXt name for these), with all the arguments defined as nonoptional. Default values for the arguments need to be handled somewhat more explicitly than with LaTeX; macros such as <tt>def\MyCommand{\dodoubleempty\ifsecondargument</tt> are used to determine whether the given argument was specified, as follows:doMyCommand} \def\doMyCommand[#1][#2]{#1Hello
Note that this makes both arguments optional -- something that is much more difficult to do On a final note, for comparative purposes: in LaTeX. This also means that we should reverse the order of arguments, since if the user specifies only one argument it will be treated as the first a new command with an optional argumentis defined with <code>\newcommand</code>.
If you don't want any optional arguments, but still want your arguments enclosed in <tttexcode>\newcommand{\MyCommand}[2]</tt> with appropriate handling for spaces (or line breaks) between the square brackets, use <tt>[World]{{#2Hello #1!}}\MyCommand{\bfseries}\dodoublearguments</tt> instead of <tt>MyCommand[Hans]{\dodoubleempty</tt>. There are of course versions for other numbers of arguments, found by replacing <tt>double</tt> with <tt>single</tt> through <tt>seventuple</tt>; see <tt>syst-gen.texscshape}</tttexcode> for the exact names.
----Reference: http://archive.contextgarden.net/message/20101215.225603.cc903e62.en.html
Also, does someone know how to define \mycommand[.1.[Category:Programming and Databases]][[.2.Category:Tools]]{.3.}? E.g., with curly braces around a non-optional third argument? I think this just involves adding a second, non-delimited argument to <tt>\doMyCommand</tt>, but I'm not sure. Also, can someone test to see if <tt>\dosingleempty</tt> and <tt>\dosingleargument</tt> can be chained, to get only one optional square-bracketed argument?
Commands with optional arguments (view source)
Revision as of 17:04, 8 June 2020
, 17:04, 8 June 2020no edit summary
In ConTeXt, the optional argument processing is handled as a two-step process. \newcommandFirst, we write the command for the end-user as a wrapper command, which calls {\MyCommand{cmd|dosingleempty}}[2][World], {{#2Hello #1!cmd|dodoubleempty}} \MyCommand, {{cmd|dotripleempty}}, ... (from {{\bfseriessrc|syst-aux.mkiv} \MyCommand[Hans]} or {{\scshapesrc|syst-gen.mkii}}) to handle the arguments properly -- including the optional ones -- and then calls a "private" command that contains the internals of the macro. Note that this function call does not explicitly refer to the arguments at all.
\ifsecondargument
#2%
\fi
!}
\MyCommand[\bf]\ %
\MyCommand[\sc][Hans]
</context>
If you ''don't'' want any optional arguments, but still want your arguments enclosed in <tt>[]</tt> with appropriate handling for spaces (or line breaks) between the square brackets, use {{cmd|dodoubleargument}} instead of {{cmd|dodoubleempty}}. There are of course versions for other numbers of arguments, found by replacing <tt>double</tt> with <tt>single</tt> through <tt>seventuple</tt>; see {{src|syst-aux.mkiv}} for the exact names.
=== Examples ===
To define <code>\mycommand[#1]{#2}</code> with one optional argument and one mandatory argument, do the following
<context source="yes">
\def\mynewcommand{\dosingleempty\doMyNewCommand}
\def\doMyNewCommand[#1]#2{%
\iffirstargument
There is an optional parameter: {\bf #1}\par%
\else
No optional parameter\par%
\fi
This is the mandatory text: {\em #2}%
}
\starttext
\mynewcommand[opt]{Hello People}
\blank
\mynewcommand{Hello People}
\stoptext
</context>
To define <code>\mycommand[#1][#2]{#3}</code> with two optional arguments and one mandatory argument, do
<texcode>
\def\mycommand{\dodoubleempty\doMycommand}
\def\doMycommand[#1][#2]#3{whatever}
</texcode>
=== Pitfalls ===
Please keep in mind that <code>\iffirstargument</code> will always return true if you put before it a command which itself has an argument. See the following example:
<context source="yes" text="produces">
\def\mynewcommand{\dosingleempty\doMyNewCommand}
\def\doMyNewCommand[#1]#2{%
\startalignment[center]
\iffirstargument
There is an optional parameter: {\bf #1}\par%
\else
No optional parameter\par%
\fi
This is the mandatory text: {\em #2}%
\stopalignment
}
\starttext
\mynewcommand[opt]{Hello People}
\blank
\mynewcommand{Hello People}
\stoptext
</context>
Use <code>\doifsomethingelse</code> instead:
<context source="yes" text="this time is correct:">
\def\mynewcommand{\dosingleempty\doMyNewCommand}
\def\doMyNewCommand[#1]#2{%
\startalignment[center]%
\doifsomethingelse{#1}
{There is an optional parameter: {\bf #1}\par}
{No optional parameter\par}
This is the mandatory text: {\em #2}
\stopalignment%
}
\starttext
\mynewcommand[opt]{Hello People}
\blank
\mynewcommand{Hello People}
\stoptext
</context>
