[texhax] Unexisting commands.

[Paul Isambert]

Dear all,

I've stumbled on the following problem. Heiko Oberdiek uses

\expandafter\ifx\csname ProvidesPackage\endcsname\relax

in his ifluatex package, whereas Till Tantau in PGF/TikZ goes

\ifx\ProvidesPackage\@undefined

so that, if you load the former before the latter, the latter goes 
wrong, since \ProvidesPackage is not undefined anymore.
Shouldn't we try to all use the same construction to test for the 
existence of commands?
If we took e-TeX for granted, then \ifcsname would solve the problem. 
Otherwise, we could try to have a rule according to which we should 
always use one way of testing and not the other. Is that unrealistic?

Best,
Paul