Werner Lemberg writes:
 > On Sun, 2 Mar 1997, Hans Aberg wrote:
 >
 > >   Actually, what is needed, is a simple extension of the TeX \def command:
 > >     \def\name<parameter text>{definition text}[exception text]
 > > If a command somehow is unable to process the parameter text, then the
 > > original input text (before the parsing of the parameter text began) is
 > > left unaffected, and the execution passes to the exception text.
 > >   Then stuff like optional commands could be implemented most easily, and
 > > perhaps the stuff you are asking for, too.
 >
 > This sounds for me like an OTP (Omega Translation Process) input filter.
 > With Omega you can do a lot of manipulation (notably character encoding
 > conversion and various more or less complicated character cluster->glyph
 > transformations e.g. for Hebrew or Arabic) of text before TeX sees the
 > text. You can avoid any active characters.

i think you are mistaken. The comments by Hans are targeted towards
general features or misfeatures (or missing features :-) of TeX's
parsing machinery. OTPs in omega are filters which means they offer a
preprocessing step but not a generally enhanced parsing functionality
of the macro language itself.

however as i said before this is not the right list to dicuss
extensions to TeX itself

frank