# [texhax] the \let command

Uwe Lück uwe.lueck at web.de
Sun Nov 26 22:43:51 CET 2006

>On Fri, 24 Nov 2006, R.Tange at soton.ac.uk wrote:
>
> > I am using (probably one of the latest versions of) Latex.
> >
> > Why does
> >
> > \let\mycedilla\c
> > \renewcommand{\c}{\ensuremath{\mathcal{c}}}
> >
> > work fine, but
> >
> > \let\tie\t
> > \renewcommand{\t}{\ensuremath{\mathfrac{t}}}
> >
> > go wrong?

If you indeed do

\let\mycedilla\c
\renewcommand{\c}{\ensuremath{\mathcal{c}}}

\show\c \show\mycedilla

\let\mycedilla\c
\renewcommand{\c}{\ensuremath{\mathcal{c}}}

\show\c \show\mycedilla

\let\tie\t
\renewcommand{\t}{\ensuremath{\mathfrac{t}}}

\show\t \show\tie

\let\tie\t
\renewcommand{\t}{\ensuremath{\mathfrac{t}}}

\show\t \show\tie

(which is not entirely clear to me) "\c" and "\t" work the
same way. (May be you must replace \show by something
like \typeout{\meaning} to escape the "Emergency stop".)
The second \let stores the result of the first \renewcommand
-- and this is, of course, the same as the result of the
second \renewcommand. -- What did you expect,

>Do you know a solution?

A suggested "solution" might be (I know it from own experience)
that the sample code in the texhax posting is not the same as
in the source files whose results are reported.

At 19:54 24.11.06, Hartmut Henkel wrote:
>\mathfrac isn't a valid LaTeX core macro. You might need a macropackage
>(which?) to activate it.

It is eufrak.sty; yet as long TeX doesn't try to evaluate it,
it needn't be "activated".

> > After executing the above two lines \t and \tie mean the same thing.
>
>no, \tie points to the _former_ \t definition, then \t is redefined.
>They don't necessarily mean the same thing.

... I wonder, wonder -- somewhat boldly: will Rudolf Tange
understand this while I don't? "necessarily mean"?
In fact, \meaning\t and \meaning\tie agree (necessarily).

Regards,

Uwe.