[comp.text.tex] Line traps?

schwartz@groucho.cs.psu.edu (Scott Schwartz) (11/18/90)

Michael Janich writes:
   >4) Why is TeX better then Troff or Nroff.
   Nobody how knows TeX would answer such a question! There is *NO*
   possibility to compare such programs.

I'm a TeX fan too, but troff has some really intersting features of
its own.  Traps and diversions, for instance.  Line traps allow you to
execute a macro at secified parts of the page, say at the beginning of
each line.  How does one elegantly get that effect in TeX?