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I had never heard of eqn and was surprised to find that the binary is still there on my Linux box. With regard to roff in general, when I got into Linux-based

I had never heard of eqn and was surprised to find that the binary is still there on my Linux box. With regard to roff in general, when I got into Linux-based typesetting around the turn of the millennium, that was already seen as antiquated tech, superseded by LaTeX which was undergoing a frenzy of development and improvement around that time. So, anyone under the age of 30 will probably be hearing of such *roff stuff for the first time (and sadly even familiarity with LaTeX has waned).

tannhaeuser 7y ago
Ok I'm probably showing my age here then :) Back in the 1980 and 1990s, the roff suite, and most definitely egrep and classic Thompson DFA construction and DFA->NFA conversion was definitely Unix folklore/taught in Uni. Manpages are still rendered using roff/groff today, so probably many of us are using it regularly. Whereas GNU's texinfo has matured less well I'd say, or wasn't even very useful in practice to begin with due to lack of content. I'm also using TeX/LaTex, but it's still a programming language whereas roff/eqn etc are non-Turing DSLs and renderers for particular narrow purposes. I get your point, but saying these are "antiquated" is like saying HTML is obsoleted by JavaScript.
- saagarjha 7y ago
  > Thompson DFA construction and DFA->NFA conversion My (very recent) university education was unfortunately quite light on UNIX folklore, but this was converted in our formal automata course as we traversed the Chomsky hierarchy.
- shakna 7y ago
  > Manpages are still rendered using roff/groff today, so probably many of us are using it regularly. I know a number of projects that generate their roff by using pandoc. They don't actually know, or have the inclination to learn, exactly how g/roff works.
- burntsushi 7y ago
  > and most definitely egrep and classic Thompson DFA construction and DFA->NFA conversion was definitely Unix folklore/taught in Uni I think you mean "Thompson NFA construction" and "NFA->DFA." Regardless though, this is not what the OP is pointing out. 'egrep' (or just GNU grep these days) is doing something more clever (emphasis mine): > Al Aho expected his deterministic regular-expression recognizer would beat Ken's classic nondeterministic recognizer. Unfortunately, for single-shot use on complex regular expressions, Ken's could finish while egrep was still busy building a deterministic automaton. To finally gain the prize, Al sidestepped the curse of the automaton's exponentially big state table by inventing a way to build on the fly only the table entries that are actually visited during recognition. Russ Cox talks about this a bit in part 3 of his articles on regex matching[1]. Its implementation in RE2 is here: https://github.com/google/re2/blob/master/re2/dfa.cc https://github.com/google/re2/blob/master/re2/dfa.cc [1] - https://swtch.com/~rsc/regexp/regexp3.html https://swtch.com/~rsc/regexp/regexp3.html
  - tannhaeuser 7y ago
    > I think you mean "Thompson NFA construction" and "NFA->DFA." Yep, only noticed it later, then left it in to see who's paying attention :)

tannhaeuser 7y ago

Ok I'm probably showing my age here then :) Back in the 1980 and 1990s, the roff suite, and most definitely egrep and classic Thompson DFA construction and DFA->NFA conversion was definitely Unix folklore/taught in Uni. Manpages are still rendered using roff/groff today, so probably many of us are using it regularly. Whereas GNU's texinfo has matured less well I'd say, or wasn't even very useful in practice to begin with due to lack of content. I'm also using TeX/LaTex, but it's still a programming language whereas roff/eqn etc are non-Turing DSLs and renderers for particular narrow purposes. I get your point, but saying these are "antiquated" is like saying HTML is obsoleted by JavaScript.

saagarjha 7y ago
> Thompson DFA construction and DFA->NFA conversion My (very recent) university education was unfortunately quite light on UNIX folklore, but this was converted in our formal automata course as we traversed the Chomsky hierarchy.
shakna 7y ago
> Manpages are still rendered using roff/groff today, so probably many of us are using it regularly. I know a number of projects that generate their roff by using pandoc. They don't actually know, or have the inclination to learn, exactly how g/roff works.
burntsushi 7y ago
> and most definitely egrep and classic Thompson DFA construction and DFA->NFA conversion was definitely Unix folklore/taught in Uni I think you mean "Thompson NFA construction" and "NFA->DFA." Regardless though, this is not what the OP is pointing out. 'egrep' (or just GNU grep these days) is doing something more clever (emphasis mine): > Al Aho expected his deterministic regular-expression recognizer would beat Ken's classic nondeterministic recognizer. Unfortunately, for single-shot use on complex regular expressions, Ken's could finish while egrep was still busy building a deterministic automaton. To finally gain the prize, Al sidestepped the curse of the automaton's exponentially big state table by inventing a way to build on the fly only the table entries that are actually visited during recognition. Russ Cox talks about this a bit in part 3 of his articles on regex matching[1]. Its implementation in RE2 is here: https://github.com/google/re2/blob/master/re2/dfa.cc https://github.com/google/re2/blob/master/re2/dfa.cc [1] - https://swtch.com/~rsc/regexp/regexp3.html https://swtch.com/~rsc/regexp/regexp3.html
- tannhaeuser 7y ago
  > I think you mean "Thompson NFA construction" and "NFA->DFA." Yep, only noticed it later, then left it in to see who's paying attention :)