ai2472206...@yeah.net schrieb am 22.10.2024 um 07:32:
Thank you so much. I think I understand its usage.
Also, regarding the "ifargument" command you mentioned,
is it counting from 0 and then checking the arguments one by one?
Because I only learned "iffirstargument", "ifsecondargument" from the wiki.
Perhaps we should update the section on the wiki on defining optional
parameters.
You can check individual argument with the old and new method but there
are differences because the new \ifparameter conditional gives a false
result when you set the optional argument but leave it empty.
%%%% begin example
\def\oldargumentcheck
{\dotripleempty\dooldargumentcheck}
\def\dooldargumentcheck[#1][#2][#3]%
{\iffirstargument
First optional argument is used.\par
\else
First optional argument isn't used.\par
\fi
\ifsecondargument
Second optional argument is used.\par
\else
Second optional argument isn't used.\par
\fi
\ifthirdargument
Third optional argument is used.\par
\else
Third optional argument isn't used.\par
\fi}
\tolerant\def\newargumentcheck[#1][#2][#3]%
{\ifparameter#1\or
First optional argument is used.\par
\else
First optional argument isn't used or empty.\par
\fi
\ifparameter#2\or
Second optional argument is used.\par
\else
Second optional argument isn't used or empty.\par
\fi
\ifparameter#3\or
Third optional argument is used.\par
\else
Third optional argument isn't used or empty.\par
\fi}
\starttext
\oldargumentcheck[][foo]
\blank
\newargumentcheck[][bar]
\stoptext
%%%% end example
When you care only about the number of argument you would use nested
argument checks in the old system but the new \ifarguments conditional
uses branches for each case like \ifcase. The order for the number of
arguments is also reversed, the old system starts with the case for all
argument and ends with zero arguments while the new check start with
zero arguments and ends with all of them.
%%%% begin example
\def\oldcommand
{\dotripleempty\dooldcommand}
\def\dooldcommand[#1][#2][#3]%
{\ifthirdargument
Three optional arguments are used.\par
\else\ifsecondargument
Two optional arguments are used.\par
\else\iffirstargument
One optional argument is used.\par
\else
No optional argument is used.\par
\fi\fi\fi}
\tolerant\def\newcommand[#1][#2][#3]%
{\ifarguments
No optional argument is used.\par
\or
One optional argument is used.\par
\or
Two optional arguments are used.\par
\or
Three optional arguments are used.\par
\fi}
\starttext
\oldcommand[][]
\blank
\newcommand[][]
\stoptext
%%%% end example
Wolfgang
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