Re: Simple command with variable number of arguments

[Aditya Mahajan <adityam@umich.edu>]

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On Fri, 23 May 2014, Matthias Weber wrote:

> Dear All,
>
> I would like to define a command that expands
>
> \vector{2,4} % or vector[2,4] if that’s easier
>
> to
>
> \startpmatrix
> \NC 2 \NR
> \NC 4 \NR
> \stoppmatrix
>
> and more generally
>
> \vector{2,4,1,7}
>
> to
>
> \startpmatrix
> \NC 2 \NR
> \NC 4 \NR
> \NC 1 \NR
> \NC 7 \NR
> \stoppmatrix
>
> Any hints how to achieve this?

Surprisingly, this is not as simple as it may seem at first glance. Some 
time ago, I had written a module to achieve this. See attached. The usage 
is:

\usemodule[simplematrix]

\definesimplematrix[MATRIX][fence=bracket]

(any predefined math-fence will work) and then:

\MATRIX{1,2,3} for row vectors and \MATRIX{1;2;3} for column vectors, and 
\MATRIX{1,2,3; 4,5,6} for matrices.

You can use \definesimplematrix[...][distance=..., align=...] to influence 
the distance and align keys of mathmatrix.

Aditya

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%D \module
%D   [     file=t-simplematrix,
%D      version=2014.02.18,
%D        title=\CONTEXT\ User Module,
%D     subtitle=Simple matrix,
%D       author=Aditya Mahajan,
%D         date=\currentdate,
%D    copyright=Aditya Mahajan,
%D        email=adityam <at> ieee <dot> org,
%D      license=Simplified BSD License]

\writestatus{loading}{Simple matrix (ver: 2014.02.18)}

\startmodule[simplematrix]

\unprotect

\definenamespace
  [simplematrix]
  [   \c!type=module,
      \c!name=simplematrix,
   \c!command=\v!yes,
        setup=\v!list,
    \s!parent=simplematrix,
  ]

\setupsimplematrix
  [
    \c!distance=\emwidth,
    \c!mathstyle=,
    fence=bracket,
    \c!align=
  ]

\appendtoks
  \setevalue{\currentsimplematrix}{\usesimplematrix[\currentsimplematrix]}
\to \everydefinesimplematrix

\newtoks\simplematrixtoks

\define[1]\simplematrix_row
    {\processcommalist[#1]\simplematrix_col
     \appendtoks \NR \to \simplematrixtoks}

\define[1]\simplematrix_col
    {\appendtoks \NC #1 \to \simplematrixtoks}

\unexpanded\def\usesimplematrix
    {\dodoubleargument\usesimplematrix_indeed}

\def\simplematrix_left
    {\edef\p_left{\namedmathfenceparameter{\simplematrixparameter{fence}}\c!left}%
     \normalleft\ifx\p_left\empty.\else\Udelimiter\plusfour\fam\p_left\relax\fi
     \,}

\def\simplematrix_right
    {\edef\p_right{\namedmathfenceparameter{\simplematrixparameter{fence}}\c!right}%
     \,
     \normalright\ifx\p_right\empty.\else\Udelimiter\plusfive\fam\p_right\relax\fi}
     

\def\usesimplematrix_indeed[#name][#options]#matrix%
    {\begingroup
     \edef\currentsimplematrix{#name}%
     \setupsimplematrix[#name][#options]%
     \simplematrixtoks\emptytoks
     \startusemathstyleparameter\simplematrixparameter
     \appendtoks 
           \bgroup
           \startmathmatrix
            [
              \c!distance=\simplematrixparameter\c!distance,
              \c!left=\simplematrix_left,
              \c!right=\simplematrix_right,
              \c!align=\simplematrixparameter\c!align,
            ]
        \to \simplematrixtoks
     \processlist[];\simplematrix_row[#matrix]%
     \appendtoks \stopmathmatrix \egroup \to \simplematrixtoks
     \the\simplematrixtoks
     \stopusemathstyleparameter
     \endgroup}

\protect

\stopmodule

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