How to define a macro to create a new macro with a name passed as its argument?

Question

I want to define a macro \create that accept a single mandatory argument from which another new macro is created and named.

The following code snippet may speak clearer what I want to achieve. But the following code cannot be compiled because it is wrong. :-)

\documentclass{article}

\newcommand\create[1]{%
\newcommand\#1{My name is #1}}

\begin{document}
\create{test}
\test
\end{document}

How to define a macro to create a new macro with a name passed as its argument?

Answer 1

Use \csname #1\endcsname which must be expanded before \newcommand using \expandafter:

\newcommand\create[1]{%
\expandafter\newcommand\csname #1\endcsname{My name is #1}}
% usage: \create{foobar}

If you want to pass the macro as control sequence instead, i.e. \foobar instead of foobar then you need to turn it into a string and remove the backslash:

\makeatletter
\newcommand\create[1]{%
\expandafter\newcommand\csname\expandafter\@gobble\string#1\endcsname{My name is #1}}
\makeatother
% usage: \create{\foobar}

There is also the \@namedef macro which is defined as \expandafter\def\csname #1\endcsname, so you can use it as:

\newcommand\create[1]{\@namedef{My name is #1}}

The etoolbox package also provides a basically identical, but robust macro called \csdef. For both you can provide a parameter text, e.g. for arguments direct after the name argument: \csdef{name}#1#2{some code with two arguments #1 and #2} (the # have to be doubled inside another macro).

Answer 2

\documentclass{article}

\newcommand\create[1]{%                                                         
\expandafter\def\csname #1\endcsname{My name is #1}}

\begin{document}
\create{test}
\test
\end{document}

Answer 3

If you're going to be doing lots of this sort of thing, you can create a bunch of macros in one go from a comma separated list with some etoolbox magic:

\usepackage{etoolbox}
\newcommand\create[1]{%
\expandafter\newcommand\csname #1\endcsname{My name is #1}}
\newcommand\createlist{%
\let\do\create
\docsvlist
}

The argument of \createlist should be a list like: \createlist{foo,Foo,magic,jabberwocky} and it will create \foo,\Foo,\magic,\jabberwocky

Answer 4

If you want to pass the macro name as a macro name:

\documentclass{article}

\newcommand{\create}[1]% #1 = macro name
{\bgroup
  \def\foo{Hello World!}% local definition
  \global\let#1=\foo
\egroup}

\begin{document}
\create{\mymacro}%
\mymacro
\end{document}