Philip Taylor wrote:
> Reinhard Kotucha wrote: > >> And pdftex is 100% backwards compatible with DEK's TeX. > > Well, not really : compare the result of expanding (e.g.,) > > \expandafter \ifx \csname pdfximage\endcsname \relax UNDEFINED\else > DEFINED\fi > > in the two engines ... and of course, for exactly analogous reasons (\expandafter \ifx \csname holdinginserts\endcsname \relax UNDEFINED\else DEFINED\fi), TeX 3 cannot be 100% backwards-compatible with TeX 82. But there may be other reasons as well, which it is too late for me to think of this evening. ** P.
