Documentation of loop over item

Question

In this answer there is a loop construct used called loop over item. I am looking for a documentation of this and for a reference in which file it is defined.

 \ifdate{workday} {
  \tikzset{every workday/.try, vacation name=,
    loop over item/.code args={##1/##2/##3}{%
      \ifdate{between=##1 and ##2}{%
        \tikzset{every vacation/.try, vacation name/.expanded=##3}%
      }{}},
    loop over item/.list/.expanded=\vacations}%
  }{}

I already searched the tikz documentation for it and grepped my texlive directory but didn't find it.

The .list thingy is explained on page 890 of the pgfmanual. The whole section 82 is a great reference for the pgfkeys, which are at work here. As far as I understand things, the .list key makes the key before loop over whatever is after the = sign (\avations in this case, which also gets expanded because of the .expanded key). BTW, as far as I understand things, this loop over item by itself is, despite what its name suggests, not a loop, but "just" a code. However, due to the .list key, it becomes a loop — , Sep 27 '18 at 19:46
loop over item/.code=blah suggests that it is a user-defined macro. There should not be documentation. — Symbol 1, Sep 27 '18 at 21:02

score 3 · Accepted Answer · 2018-09-27T20:31:16.333

Everything I am going to say here is much better explained in section 82 of the pgfmanual. loop over item by itself is, despite what its name suggests, not a loop, but "just" a code. However, due to the .list key, it becomes a loop. To see that more clearly, consider the MWE

\documentclass{article}
\usepackage{pgfkeys,pgffor} % .list requires pgffor
\begin{document}
\pgfkeys{/student/.cd, % switch to student
hello/.code={hello #1!}}
\pgfkeys{/student/hello=world}

\pgfkeys{/student/hello/.list={world,duck,koala,marmot}}
\end{document}

Here, hello is just a simple code that prints hello <arg>!, where arg is the argument. (If you have a definition inside a definition, you need to increase the number of #, as explained e.g here. This is the reason why there are two # in the definition of \ifdate.)

What is important now is that the .list key makes the code loop over the argument, as can be seen in (the admittedly stupid example) \pgfkeys{/student/hello/.list={world,duck,koala,marmot}}. Note also that .list requires the pgffor library (on top of pgfkeys, which would be sufficient to make the first part of the MWE work).

Documentation of loop over item

1 Answers1