[texhax] the \let command

[Hartmut Henkel]

On Sun, 26 Nov 2006, Uwe Lück wrote:

> > 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?

> 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".

ah, thanks, and sure we need to _load_ the macropackage eufrak.sty, if
we want to _use_ \mathfrac. By "activate" i meant something like "make
it available" for use, somewhat fuzzy. As the "points" in the next line.

> > 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).

in german it would be "nicht notwendigerweise" or "nicht zwingend",
maybe my translation is bad. Well, from Rudolf Tanges original mail i
had condensed a minimal example to see what's going on, and here is a
version with what i have learnt in the meanwhile from you (eufrak) and
with your sentence above:

\documentclass{article}
\usepackage{eufrak}
\begin{document}

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

In fact, \meaning\t and \meaning\tie agree (necessarily).

\end{document}

(We should always use minimal examples.) Obviously \meaning\t and
\meaning\tie in fact don't agree in this example (i described also,
why). So it's not necessarily so, as it depends also on the past. E. g.
one can force it, as you do by the double \renewcommand. But this was
not part of the original question. If you want \meaning\t and
\meaning\tie agree (necessarily), you can simply write:

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

Regards, Hartmut