# [texhax] the \let command

Philip TAYLOR P.Taylor at Rhul.Ac.Uk
Mon Nov 27 18:31:17 CET 2006

tom sgouros wrote:

>> Surely because \t is recursively defined in terms of itself,
>> n'est-ce pas ?
>
> Bien sur.  But there is clearly something stunningly obvious to you that
> is not at all clear to me, and a little more detail would be gratefully

With pleasure ...

>  o Are you talking about the original definition of \t that is
>    recursive, or is there something incorrect in my redefinition of \t?

The original : \t -> macro :-> \OML-cmd \t \OML\t

>  o How would I have known \t was recursively defined?

As I did : by asking \TeX to shew the meaning of \t :

\meaning \t

>  o Why is \t recursively defined?

Only the Great and the Good (a.k.a. the LaTeX-3 team) may
know the answer to that question; lesser mortals such as you
and I may never know ...

>  o In what way does the recursive definition interfere with the \let?

In that when \tie is expanded, it refers to \t, which has in the
meantime be redefined.

>  o How can I predict similar problems?

I am sure that Martin, Reinhard and maybe the other members of
the LaTeX thought-police will hasten to assure us all that had
we listened to them, and written in pure, 100%, LaTeX, this
problem could never have arisen ...

> If, perhaps, you can point me or the original poster to adequate
> documentation of whatever features are creating this situation, that
> would be fine.  As it is, your answer leaves the situation even more
> opaque to me now.

I apologise : I thought a simple reference to the recursive definition
of \t would be sufficient.

** Phil.