macros - calling a command using an input variable

Question

In the process of a project, I realized it would be helpful if I could do as follows. Say I have a list of different commands (simplified):

\newcommand{\AA}{...}
\newcommand{\AB}{...}
\newcommand{\AC}{...}
...
\newcommand{\AZ}{...}

Now I want a command that can call one of these commands (based on input):

\newcommand{\caller}[1]{\A#1}

The example above won't work, but how would I go accomplishing something that has such a functionality?

Answer 1

You have to construct the macro name with \csname A#1\endcsname.

In fact, a lot of package or class code makes use of this \csname ...\endcsname construction and it's not restricted to LaTeX, since both macros are TeX primitives actually.

Please note: \AA is already defined, providing a Scandinavian character, i.e.s something like Å (But since the command names seemed to be simplified, this won't be an issue, I think)

If \A#1 is not defined \csname A#1\endcsname expands to \relax, i.e. it does nothing.

\documentclass{article}



\newcommand{\AB}{bar}
\newcommand{\AC}{foobar}

\newcommand{\caller}[1]{%
  \csname A#1\endcsname%
}


\begin{document}
\caller{A}

\caller{B}

\caller{C}

\caller{Z}
\end{document}

As you can see \caller{A} works (since \AA is defined) and \caller{Z} does nothing (since \AZ isn't defined)