# [NTG-context] How to "\processcommalist"?

Taco Hoekwater taco at elvenkind.com
Fri Jul 1 19:54:02 CEST 2005

Mojca Miklavec wrote:
> I would like to define a command, which would be called in the following way:
>     \TheBossWantsTheWorkToBeDoneOn[monday,wednesday,thursday]{tidy up}
>
> so that it would be equivalent to:
>     \WeHaveToDo[monday]{tidy up}
>     \WeHaveToDo[wednesday]{tidy up}
>     \WeHaveToDo[thursday]{tidy up}
>
> I played a bit with different variants of \processcommalist, but I
> can't figure out how to use it in this particular case.

The trick is to store the tidy up inside the processing command,
like so:

\def\WeHaveToDo[#1]#2{\message{(#1: #2)}}

\def\TheBossWantsTheWorkToBeDoneOn[#1]#2%
{\begingroup
\def\processitem##1{\WeHaveToDo[##1]{#2}}%
\processcommalist[#1]\processitem
\endgroup }

\TheBossWantsTheWorkToBeDoneOn[monday,wednesday,thursday]{tidy up}

> Is there also a possibility to define a command like

There was not, but knowing Hans I trust that soon there will be :-).

For now, here is my solution.

% a few auxiliary core macros are needed to uncompress the list.
%
% \uncompresslist is the twin of the already existing \compresslist
% which works in the other direction (syst-new)
%
\unprotect

% I guess this function is already available but couldnt find it...
%
\def\apptomac#1#2%
{\ifx#1\empty\def#1{#2}\else \@EA\def\@EA#1\@EA{#1,#2}\fi}

% the next macro does this:
%
% \itemwithdash<<9-11>>- => \dorecurse {<<1+11-9>>}
%     {\apptomac\uncompressedlist<<9-1+\recurselevel>>}
%
% (the 1+ and -1 are needed to solve a counter offset.)
\def\itemwithdash#1-#2-%
{\@EA\dorecurse\@EA
{\the\numexpr 1+#2-#1\relax}%
{\@EA\apptomac\@EA\uncompressedlist\@EA
{\the\numexpr #1-1+\recurselevel\relax}}}%

% top level. The result will be in \uncompressedlist
\def\uncompresslist[#1]%
{\def\uncompressedlist{}%
\def\processitem##1%
{\doifinstringelse{-}{##1}
{\itemwithdash##1-}
{\apptomac\uncompressedlist{##1}}}%
\processcommalist[#1]\processitem }

\protect

% end support macros.

With these, you can do:

{\begingroup