How to change the item separator in TikZ foreach command

Question

I want to cycle over several sentences using a foreach loop. Now sentences will prpbably contain commas, which are used by foreach as item separators. So I would like to change the item separator to something that does not appear in my sentences, like e.g. |

So instead of

\foreach \x in {sentenceA,sentenceB,sentenceC}

I would like to use

\foreach \x in {sentenceA|sentenceB|sentenceC}

Is this possible?

I thought about that, but that wouldn't be easy to automate, as sentences may also contain dots (like in e.g.) where I don't want a separation. Manually putting .| at the end of a sentence will be much easier (or !| or ?|) — Tom Bombadil, Sep 19 '12 at 10:53

score 14 · Accepted Answer · answered Sep 19 '12 at 13:12

Here's an expl3 implementation:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{xparse,pgffor}
\ExplSyntaxOn

\NewDocumentCommand{\Foreach}{ m O{,} m}
 {
  \__foreach_main:nn { #1 } { #2 } { #3 }
 }

\seq_new:N \l__foreach_arg_seq
\clist_new:N \l__foreach_braced_clist

\cs_new_protected:Npn \__foreach_main:nn #1 #2 #3
 {
  \seq_set_split:Nnn \l__foreach_arg_seq { #2 } { #3 }
  \clist_clear:N \l__foreach_braced_clist
  \seq_map_inline:Nn \l__foreach_arg_seq
   {
    \clist_put_right:Nn \l__foreach_braced_clist { { ##1 } }
   }
  \foreach #1 in~\l__foreach_braced_clist
 }
\ExplSyntaxOff

\begin{document}

\Foreach{\x}[|]{sentenceA|se,nt,en,ce,B| sentenceC }{[\x]}

\Foreach{\x}{sentenceA|se,nt,en,ce,B| sentenceC }{[\x]}

\end{document}

The syntax is a bit different than \foreach \x in {...}, but this shouldn't be a big problem. The default separator is the comma, a different one can be specified in the optional argument after the variable.

enter image description here

How to use this Foreach command in the case of \foreach [some options] \x in. Should I add an optional <> parameter for the loop options ? — Tarass, Apr 28 '14 at 19:37
See my proposition below. The new command does not use foreach itself but prepare the string to be foreach compatible, then you can freely use all foreach options. — Tarass, Apr 29 '14 at 04:40

score 11 · Answer 2 · answered Sep 19 '12 at 11:26

The comma is hardcoded in pgffor's \foreach. You could convert the list before and store it in a macro. The following example puts the entries in curly braces to protect the commas. Then initial and final spaces are also kept. In the example only an initial space is removed.

\documentclass{article}
\usepackage{pgffor}

\makeatletter
\newcommand{\tocommalist}[3]{%
  \begingroup
    \toks@{}
    \let\@tmp\relax
    \long\def\@tocommalist##1#2##2\@nil{%
      \ifx\@tmp\relax
        % \toks@{{##1}}% without initial trimming
        \toks@\expandafter{\expandafter{\romannumeral-`\x##1}}%
      \else
        % \toks@\expandafter{\the\toks@,{##1}}% without initial trimming
        \toks@\expandafter{%
          \the\expandafter\toks@\expandafter,%
          \expandafter{\romannumeral-`\x##1}%
        }%
      \fi
      \def\@tmp{##2}%
      \ifx\@tmp\@empty
        \expandafter\@gobbletwo
      \fi
      \@tocommalist##2\@nil
    }%
    \@tocommalist#3#2\@nil
  \expandafter\endgroup
  \expandafter\def\expandafter#1\expandafter{\the\toks@}%
}
\makeatother

\tocommalist\mylist{|}{sentenceA|se,nt,en,ce,B| sentenceC }
\foreach \x in \mylist {%
  \typeout{[\meaning\x]}%
}

\begin{document}
\foreach \x in \mylist {%
  [\x]\par
}
\end{document}

Result

Another example using package etoolbox. It also only trims the beginning of the entry and it removed empty entries:

\documentclass{article}

\usepackage{pgffor}
\usepackage{etoolbox}
\usepackage{etexcmds}
\DeclareListParser*{\forvertlist}{|}

\makeatletter
\newcommand{\vertocomma}[2]{%
  \let#1\@empty
  \forvertlist{\@verttocomma{#1}}{#2}%
}
\newcommand{\@verttocomma}[2]{%
  \edef#1{%
    \ifx#1\@empty
    \else
      \etex@unexpanded\expandafter{#1},%
    \fi
    {\etex@unexpanded{#2}}%
  }%
}
\makeatother

\vertocomma\mylist{sentenceA|| |se,nt,en,ce,B| sentenceC |}
\foreach \x in \mylist {%
  \typeout{[\meaning\x]}%
}

\begin{document}
\foreach \x in \mylist {%
  [\x]\par
}
\end{document}

Ahmed Musa · Answer 3 · 2012-09-21T03:35:42.687

When no auto-list-completion is required, catoptions package's \indrisloop can handle any list separator. The \newforeach macro can naturally accept any type of list separator and it can do list completion, but it is not yet on CTAN. Here is a \indrisloop solution. This should work even when the list separator was active. As you will notice in the result of the example, spurious spaces between the elements of the list are removed.

\documentclass{article}
\usepackage{catoptions}

\begin{document}

\def\bombadil#1{%
  \typeout{Doing item: #1}%
  \edef\transformedlist{%
    \ifdefFT\transformedlist{}{\expandcsonce\transformedlist}%
    \unexpanded{\\{#1}}%
  }%
}

% \indrisloop[<separator>]{<list>}{<callback>}

\indrisloop[|]{%
  David Carlisle, item 1 |
  Heiko Oberdiek, item 2 |
  David Salomon, item 3 |
  Frank Mittelbach, item 4 |
  Donald Arseneau; item 5
}\bombadil

\show\transformedlist
\end{document}

{\show}
> \transformedlist=macro:

\\{David Carlisle, item 1}\\{Heiko Oberdiek, item 2}\\{David Salomon, item 3}
\\{Frank Mittelbach, item 4}\\{Donald Arseneau; item 5}.

l.21 \show\transformedlist

D.E. Knuth liked to use \\ as a list separator.

You can transform an arbitrary list into a comma-separated list using the following \makeintocommalist.

% \makeintocommalist{<original.parser>}{<orig.list.cmd>}{<transformed.list.cmd>}

\def\makeintocommalist#1#2#3{%
  \def#3{}%
  \def\bombadil##1{%
    \edef#3{%
      \expandcsonce#3{\unexpanded{##1}}%
      \iflastindris\else,\fi
    }%
  }%
  \indrisloop*[#1]{#2}\bombadil
}

Example:

\def\alist{%
  David Carlisle, item 1 |
  Heiko Oberdiek, item 2 |
  David Salomon, item 3 |
  Frank Mittelbach, item 4 |
  Donald Arseneau; item 5 |
  Enrico Gregorio/another great |
  Ulrich Diez, yes! |
  Joseph Wright, also/+
}

\makeintocommalist{|}\alist\blist
\show\blist

> \blist=macro:->

{David Carlisle, item 1},{Heiko Oberdiek, item 2},{David Salomon, item 3},
{Frank Mittelbach, item 4},{Donald Arseneau; item 5},{Enrico Gregorio/another great},
{Ulrich Diez, yes!},{Joseph Wright, also/+}.

l.53 \show\blist

EDIT

Now I remember that the catoptions package has a \cptforeach command that does exactly what you wanted. But it doesn't do auto-completion of lists. See it in action below. It is happy with arbitrary (even weird) list item separators.

% \cptforeach[<optional.sep>] <holders> \in <list> \do {<callback>}

% Note the list separators in these loops:

\tikz[shading=ball]
  \cptforeach[:] \x+\cola \in 0+red : 1+green : 2+blue : 3+yellow \do {%
    \cptforeach[|] \y;\colb \in {0;red | 1;green | 2;blue | 3;yellow} \do {%
      \shade[ball color=\cola!50!\colb] (\x,\y) circle (0.4cm);
  }%
};

enter image description here

The above is equivalent to

\tikz[shading=ball]
  \cptforeach \x/\cola \in 0/red, 1/green, 2/blue, 3/yellow \do {%
    \cptforeach \y/\colb \in {0/red, 1/green, 2/blue, 3/yellow} \do {%
      \shade[ball color=\cola!50!\colb] (\x,\y) circle (0.4cm);
  }%
};

Mark Wibrow · Answer 4 · 2014-04-29T18:42:54.910

A little late to the game, but a short and simple hack is sufficient to include both the ... notation and coordinate parsing:

\documentclass[border=5]{standalone}
\usepackage{tikz}
\makeatletter
\let\pgffor@dotsscanend@original=\pgffor@dotsscanend
\def\pgffor@setdelimiter#1{%
  \def\pgffor@emptyvalues{#1 \pgffor@stop#1}%
  \def\pgffor@normal@list##1{%
    \def\pgffor@values{##1#1 \pgffor@stop#1}%
    \ifx\pgffor@values\pgffor@emptyvalues
      \def\pgffor@values{\pgffor@stop#1}%
    \fi%
    \let\pgffor@body=\pgfutil@empty%
    \global\pgffor@continuetrue%
    \pgffor@collectbody}%
  \def\pgffor@scanround(##1)##2#1{\def\pgffor@value{(##1)##2}\pgffor@scanned}%
  \def\pgffor@scanone##1#1{\def\pgffor@value{##1}\pgffor@scanned}%
  \def\pgffor@dotsscanend##1#1{\pgffor@dotsscanend@original##1,}%
}

\pgfkeys{/pgf/foreach/delimiter/.code=\pgffor@setdelimiter{#1}}
\begin{document}
\begin{minipage}{4in} \tt
\foreach \i in {the,{quick, brown},fox,jumps,over,the,lazy,dog}{[\i]}
\\\color{red}
\foreach \i [delimiter=*] in {the*quick, brown*fox*jumps*over*the*lazy*dog}{[\i]}
\\\color{blue}
\foreach \i [delimiter=|] in {the|quick, brown|fox|jumps|over|the|lazy|dog}{[\i]}
\\\color{green}
\foreach \i [delimiter=+] in {1+...+15}{[\i]}
\\\color{purple}
\foreach \i [delimiter=!] in {(1,0)!(2,1)!(3,1)!(5,4)!(0,1)!(8,2)!(4,3)}{[\i]}
\end{minipage}
\end{document}

enter image description here

I understand ... but what do you mean by "coordinate parsing" ? Could you give an example ? — Tarass, Apr 29 '14 at 12:14
@Tarass \tikz\foreach \p in {(0,3),(1,4),(2,3),(3,1)}\fill \p circle [radius=.1]; — Mark Wibrow, Apr 29 '14 at 13:39

score 3 · Answer 5 · answered Sep 19 '12 at 11:28

3

uses parentheses { aaa,nnn!} to separate items

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}

\foreach \nn in{{0,1},{1,0},{0,-1},{-1,0}}{
\draw (0,0) -- (\nn);
}
\end{tikzpicture}

\end{document}

enter image description here

answered Sep 19 '12 at 11:28

rpapa

12,350

1

I know that it can be done like this, but that's just what I wanted to avoid (see Andrew Stacey's comment on my question). – Tom Bombadil Sep 19 '12 at 11:34

Tarass · Answer 6 · 2014-04-29T14:16:38.477

Full foreach options compatible solution.

The idea is to prepare the loop-string to be foreach compatible ie to substitute the significative comma by a phantom caractere before replace the alternative separator by the foreach-needed comma. Then in the foreach loop itself, to remplace the eventually phantom caractere by a significative comma.

enter image description here

\documentclass[french]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{babel}          % compatibilité avec Babel
\usepackage{babel}
\usepackage{xparse,xstring,tikz}
%\usetikzlibrary{}

\NewDocumentCommand{\FENewList}{
    D<>{\&}     % phantom substitution caractere
    O{;}        % alternative separator
    m           % input list
    O{\FEList}  % output list
    }{%
    \StrSubstitute{#3}{,}{#1}[#4]
    \StrSubstitute{#4}{#2}{,}[#4]
    }

\NewDocumentCommand{\FERestore}{
    D<>{\&}     % phantom substitution caractere
    m           % input string
    }{%
    \StrSubstitute{#2}{#1}{,}[#2]%
    }

\begin{document}

With for \texttt{;} as alternative separator:

\FENewList{sentenceA;se,nt,en,ce,B; sentenceC }
\foreach \x in \FEList {%
\FERestore{\x}
[\x]}

\medskip
With for \texttt{|} as alternative separator:

\FENewList[|]{sentenceA|se,nt,en,ce,B| sentenceC }
\foreach \x in \FEList {%
\FERestore{\x}
[\x]}

\medskip
With for \texttt{foreach} options:

\FENewList[|]{sentenceA|se,nt,en,ce,B| sentenceC }
\foreach \x [count=\i from 1] in \FEList {%
\FERestore{\x}
\noindent\i: [\x]\\}

\FENewList[|]{3|...|5}
\foreach \x in \FEList {%
\FERestore{\x}
\x }

\begin{tikzpicture}

\FENewList{(0,3);(1,4);(2,3);(3,1)}
\foreach \p in \FEList 
{
\FERestore{\p}
\fill \p circle [radius=.1] ;
} 

\end{tikzpicture}

How to change the item separator in TikZ foreach command

6 Answers6

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