Definining commands/abbreviations that contain numbers

Question

I tend to use \newcommand to define macros for symbols I use often, e.g. \newcommand{\hankel}{H^{(1)}_0}. One inconvenience of this approach is the fact that command names cannot include numbers. What I ideally want is to map something like \H0 to H^{(1)}_0. I imagine this could be done with some macro expansion/snippet package, or one might use \newcommand to define a command that takes a parameter, etc. Before I start experimenting, though -- is there a canonical way of dealing with this problem?

Answer 1

Defining commands with parameters would be the way I would deal with this.

\newcommand{\H}[1]{H^{(1)}_{#1}}

defines a command with one parameter. You can then do \H0, \H1, ..., \H9. For nore than one digit, you will have to use it as \H{10}.

Answer 2

This faq answer discusses this issue, criticises 4 possible ways of using such a macro and ultimately comes to the conclusion don't do that.

Answer 3

A bad hack (Jan's answer above is much better) :-):

\newcommand{\HH}{\afterassignment\HH@aux\count0=}
\newcommand{\HH@aux}{H^{(1)}_{\the\count0}}

between the usual \makeatletter and \makeatother. If you want to define the commands for various numbers separately, you can do

\makeatletter
\newcommand{\GG}{\afterassignment\GG@aux\count0=}
\newcommand{\GG@aux}{\csname GG\the\count0\endcsname}
\makeatother

and define the various \GG0, \GG1... as

\expandafter\newcommand\csname GG0\endcsname{%
  Definition of GG0.}
\expandafter\newcommand\csname GG1\endcsname{%
  Definition of GG1.}

\GG0 \GG1 \GG2 ...

Note that when we call \GG followed by 2, we don't get any error/warning: it is just ignored. This method could seem good, but it has many drawbacks, failing in unexpected cases. For instance, if \foo is say, 123, then

\GG1\foo...

will be seen as \GG1123, not the expected behaviour.