Nroff, and other macro processors like m4 or GPP, copy input to output, possibly executing macros or substituting pieces of text. It's kind of hard to make a t

Nroff, and other macro processors like m4 or GPP, copy input to output, possibly executing macros or substituting pieces of text. It's kind of hard to make a text file that isn't a macro for m4, for example. That's a vacuous quine.