Applying a command to a whole column spawning “\ignorespaces”

Question

I am trying to apply a styling command to every cell of a table's column.

I define a new command invoking minted:

\newcommand{\ccode}[1]{\mintinline{c}{#1}}

And then, I apply this command in the header definition of a table:

\begin{tabular}{| >{\ccode}{l} | l |}

However, this results in some \ignorespaces randomly popping in the output file.

The following is an MWE and the corresponding output.

\documentclass{article}

\usepackage{minted}
\usepackage{collcell}

\newcommand{\ccode}[1]{\mintinline{c}{#1}}

\begin{document}

\begin{tabular}{| >{\ccode}{l} | l |}
    \hline
    int foo (int a, int b) & Foos a and b. \\ \hline
    int bar (int* a, int* b) & Bars a and b. \\ \hline
\end{tabular}

\end{document}

Has anyone an idea about what is going on? Could it be related to the minted package?

I am running TeX Live 2013 on a Ubuntu 14.04.

Thanks for your help.

---

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Answer 1

Usually, LaTeX adds \ignorespaces at the begin of a cell and \unskip at its end to automatically remove spaces at the begin and end of the cell contents.

The example loads package collcell, but does not use it. An example of its usage:

\documentclass{article}

\usepackage{minted}
\usepackage{collcell}

\newcommand{\ccode}[1]{\mintinline{C}{#1}}

\begin{document}

\begin{tabular}{| >{\collectcell{\ccode}}l<{\endcollectcell} | l |}
    \hline
    int foo (int a, int b) & Foos a and b. \\ \hline
    int bar (int* a, int* b) & Bars a and b. \\ \hline
\end{tabular}

\end{document}

PS: I had to use C (uppercase) as language name to get the proper output.

Analysis of the problem in the MWE of the question

First the MWE of the question with some modifications:

• Uppercase C as language name,
• Package collcell is not needed, but it loads package array, which implements < and > for the columns specification of the table.

Modified MWE:

\documentclass{article}

\usepackage{array}
\usepackage{minted}

\newcommand{\ccode}[1]{\mintinline{C}{#1}}

\begin{document}

\begin{tabular}{| >{\ccode}l | l |}
    \hline
    int foo (int a, int b) & Foos a and b. \\ \hline
    int bar (int* a, int* b) & Bars a and b. \\ \hline
\end{tabular}

\end{document}

\ccode is inserted in front of the cell contents. LaTeX automatically surrounds the cell contents with \ignorespaces and \unskip to remove spaces at the begin and end of a cell. Then the first cell becomes:

 \ccode \ignorespaces int foo (int a, int b)\unskip

Since curly argument braces are missing, the argument of \ccode is the first token \ignorespaces. The remaining part int foo (int a, int )\unskip is set as plain text.

\unskip could be used as end token for the argument and \ignorespaces can be absorbed by adding it to the parameter text of the definition of \ccode:

\def\ccode\ignorespaces#1\unskip{\mintinline{C}{#1}}

Full example:

\documentclass{article}

\usepackage{array}
\usepackage{minted}

\def\ccode\ignorespaces#1\unskip{\mintinline{C}{#1}}

\begin{document}

\begin{tabular}{| >{\ccode}l | l |}
    \hline
    int foo (int a, int b) & Foos a and b. \\ \hline
    int bar (int* a, int* b) & Bars a and b.\\ \hline
\end{tabular}

\end{document}

Package cellcoll hides these internals, providing a more readable and maintainable interface.