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Commands with optional arguments (view source)
Revision as of 23:25, 15 December 2010
, 23:25, 15 December 2010→Examples
\stoptext
</context>
=== 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>
[[Category:Inside ConTeXt]]
