Comma delimited list - how to obtain the length?

Question

It's simple. I have a list like {0,1,54,1,3} as input argument to a command in making. How can I obtain the length of this list? Something like

\length(#1)

where #1 is the list.

Answer 1

My first LaTeX3 answer! Yay! :)

The l3clist package has a lot of built-in commands to deal with comma-separated lists. Here's an attempt:

\documentclass{article}

\usepackage{expl3}
\usepackage{xparse}

\ExplSyntaxOn

\NewDocumentCommand \countItems { m } {
    \clist_count:N #1
}

\NewDocumentCommand \countInlineItems { m } {
    \clist_count:n {#1}
}

\ExplSyntaxOff

\begin{document}

\def\mylist{0,1,54,1,3}

This list has \countInlineItems{0,1,54,1,3} elements.

And the same list has \countItems{\mylist} elements.

\end{document}

Please note that we have two different usages: one for a stored list (e.g, \mylist) and one for an inline list. Thanks to Joseph for point the flaws in my code. :)

Hope it helps. :)

Answer 2

A loop and a counter:

Code

\documentclass{article}
\makeatletter
\newcommand*{\length}[1]{%
    \@tempcnta\z@
    \@for\@tempa:=#1\do{\advance\@tempcnta\@ne}%
    The length of the list #1 is \the\@tempcnta.%
}
\makeatother
\begin{document}
\length{0,1,54,1,3}

\def\mylist{0,1,54,1,3}
\length\mylist
\end{document}

Output

The length of the list 0,1,54,1,3 is 5.

Answer 3

Package xstring, counting empty elements

A solution using package xstring. It also counts elements that are empty:

\documentclass{article}
\usepackage{xstring}
\newcommand*{\commalength}[1]{%
  \StrCount{#1,}{,}%
}
\begin{document}
\verb|{0,1,54,1,3}| has length \commalength{0,1,54,1,3}.

\verb|{,,}| has length \commalength{,,}.
\end{document}

Package kvsetkeys, counting non-empty elements

The parser \comma@parse of package kvsetkeys removes an optional space before and after an entry and removes empty entries.

\documentclass{article}

\usepackage{kvsetkeys}
\makeatletter
\newcommand*{\commalength}[1]{%
  \begingroup
    \count@=0 %
    \comma@parse{#1}{%
      \advance\count@ by 1 %
      \@gobble
    }%
    \the\count@
  \endgroup
}
\makeatother

\begin{document}
\verb|{0,1,54,1,3}| has length \commalength{0,1,54,1,3}.

\verb|{,,}| has length \commalength{,,}.
\end{document}

Answer 4

Let's try etoolbox.

This use the loop and counter approach.

\documentclass{article}

\usepackage{etoolbox}

\makeatletter
\newcounter{itemcounter}%
\newcommand{\length}[1]{%
    \setcounter{itemcounter}{0}%
    \renewcommand*{\do}[1]{\stepcounter{itemcounter}\@gobble{##1}}%
    \docsvlist{#1}%
    \theitemcounter%
}
\makeatother

\begin{document}
\length{1}\qquad \length{1,2}\qquad \length{1,2,3,f,t,w,x,y,z}
\end{document}

The command \@gobble discards its argument.