From: Jon Steinhart <firstname.lastname@example.org> To: email@example.com Subject: Re: [TUHS] troff environments, traps, and diversions (was: TeX and groff) Date: Sun, 23 Jan 2022 11:45:41 -0800 [thread overview] Message-ID: <202201231945.20NJjfab422896@darkstar.fourwinds.com> (raw) In-Reply-To: <CAKH6PiUB2Y+MaVuy4Z4K7d+DhUxc-7oTqrPbvf6xjx5er7Cypg@mail.gmail.com> On Fri, Jan 21, 2022 at 9:34 PM Branden Robinson <firstname.lastname@example.org> wrote: > > On Tue, Jan 11, 2022 at 1:25 PM Lyndon Nerenberg (VE7TFX/VE6BBM) > <email@example.com> wrote: > > A lot of people get turned off by how troff markup can often look like > > line noise. That's true, but if you spend the time to actually learn > > the syntax (and it's really not that hard), you can't help but be > > overwhelmed by the beauty of its self-consistency. Although after > > three decades I still can't wrap my head around traps and diversions > > :-P > > It seems like a lot of people get stuck on the dread trio of traps, > diversions, and environments. Some old groff documentation did not, I > think, help matters very much by characterizing them as "advanced" and > particularly by comparing diversions to pointers in C. I've been > rewriting a lot of groff's documentation over the past five years. > > Here's my attempt to introduce these 3 concepts in the groff(7) page of > the forthcoming 1.23 release. Let me know how I can improve it. (I > retiterate that it's just an introduction--there is much more detail > about all three later in the page and in groff's Texinfo manual, much of > which has parallel content to its man pages.) > > A further few language elements arise as page layouts become more > sophisticated and demanding. Environments collect formatting > parameters like line length and typeface. A diversion stores > formatted output for later use. A trap is a condition on the > input or output, tested automatically by the formatter, that is > associated with a macro, causing it to be called when that > condition is fulfilled. > > Footnote support often exercises all three of the foregoing > features. A simple implementation might work as follows. A pair > of macros is defined: one starts a footnote and the other ends > it. The author calls the first macro where a footnote marker is > desired. The macro establishes a diversion so that the footnote > text is collected at the place in the body text where its > corresponding marker appears. An environment is created for the > footnote so that it is set at a smaller typeface. The footnote > text is formatted in the diversion using that environment, but it > does not yet appear in the output. The document author calls the > footnote end macro, which returns to the previous environment and > ends the diversion. Later, after much more body text in the > document, a trap, set a small distance above the page bottom, is > sprung. The macro called by the trap draws a line across the > page and emits the stored diversion. Thus, the footnote is > rendered. > > Regards, > Branden > Foo On Lyndon's comment - if you're trying to get a new generation of troff users keep in mind that to younger folks than us line noise is a reason to get a surge protector. And if they have seen phone line noise, I still have a stack of old modems in the basement for them. And troff is a lot less like line noise that OpenOffice XML. I like the proposed improvements in the docs but would go further. o As per an earlier thread, I would explain the string/number register stuff in programming language terms; these are variables. And number registers have things like auto-increment and all that. It may be *technically* correct to say that registers are interpolated, but would be way more accessible to talk about the value of a variable. o It would be nice to have a table mapping groff constructs into those from other programming languages. Common ones, that is, not perl. Mentioned variables above, to me macros are functions, there are a few control constructs. Explain this stuff in terms that people are familiar with, try to avoid crufty language. o I think that it would be helpful to summarize that troff was originally written for smaller computers which required compromises such as the one and two character naming scheme. And a table that shows how that scheme has been compatibly expanded since. Better than hiding this in the description of every request that uses names. o I think that an important point to make about diversions is that they're a bit like scratch paper; that one can scribble on it and take measurements on them to decide what to do. For example, dumping a paragraph into a diversion and then measuring it to see if it will fit unbroken on what's left of a page. o The description of traps could be expanded. I would say something like the original traps were a vertical location on a page, and that since then the term has been overloaded with number of additional varieties. Jon
next prev parent reply other threads:[~2022-01-23 19:46 UTC|newest] Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-31 15:47 [TUHS] roff(7) Douglas McIlroy 2021-12-31 23:07 ` George Michaelson 2021-12-31 23:40 ` Larry McVoy 2022-01-01 0:56 ` [TUHS] TeX and groff (was: roff(7)) Greg 'groggy' Lehey 2022-01-01 3:15 ` Larry McVoy 2022-01-10 19:00 ` Blake McBride 2022-01-10 20:21 ` Jon Forrest 2022-01-11 22:48 ` Blake McBride 2022-01-11 23:18 ` Larry McVoy 2022-01-12 1:19 ` Dave Horsfall 2022-01-12 1:46 ` Blake McBride 2022-01-12 2:12 ` Bakul Shah 2022-01-12 15:49 ` Larry McVoy 2022-01-12 16:22 ` Adam Thornton 2022-01-12 0:06 ` Jon Steinhart 2022-01-12 1:48 ` Blake McBride 2022-01-12 0:29 ` Nemo Nusquam 2022-01-12 1:53 ` Blake McBride [not found] ` <E3CC4B8A-4E88-4339-A4D3-4ED26BA80620@gmail.com> 2022-01-12 0:44 ` Jon Forrest 2022-01-12 2:00 ` Blake McBride 2022-01-12 2:10 ` David Arnold 2022-01-12 2:26 ` Adam Thornton 2022-01-12 19:54 ` John Cowan 2022-01-13 10:13 ` Thomas Paulsen 2022-01-13 20:00 ` John Cowan 2022-01-10 20:33 ` Larry McVoy 2022-01-10 20:37 ` Richard Salz 2022-01-10 21:04 ` Dan Cross 2022-01-10 21:48 ` Nemo Nusquam 2022-01-11 2:25 ` Lyndon Nerenberg (VE7TFX/VE6BBM) 2022-01-11 2:47 ` Larry McVoy 2022-01-22 2:34 ` [TUHS] troff environments, traps, and diversions (was: TeX and groff) Branden Robinson 2022-01-22 16:02 ` Douglas McIlroy 2022-01-23 19:45 ` Jon Steinhart [this message] 2022-01-23 22:26 ` Jon Steinhart 2022-01-11 1:52 ` [TUHS] Recognizing TeX (was: TeX and groff (was: roff(7))) Greg 'groggy' Lehey 2022-01-12 1:19 ` [TUHS] TeX and groff (was: roff(7)) Mary Ann Horton 2022-01-12 2:03 ` Blake McBride 2022-01-12 2:10 ` Bakul Shah 2022-01-12 3:44 ` Dan Cross 2022-01-12 16:48 ` Steffen Nurpmeso 2022-01-10 20:46 ` Steffen Nurpmeso 2022-01-11 1:59 ` [TUHS] Demise of " Greg 'groggy' Lehey 2022-01-11 2:13 ` Lyndon Nerenberg (VE7TFX/VE6BBM) 2022-01-11 2:42 ` Larry McVoy 2022-01-11 5:12 ` Greg 'groggy' Lehey 2022-01-11 5:59 ` John Labovitz 2022-01-11 8:57 ` arnold 2022-01-11 20:15 ` Jon Steinhart 2022-01-11 20:22 ` Larry McVoy 2022-01-11 20:26 ` Jon Steinhart 2022-01-11 20:36 ` Larry McVoy 2022-01-11 20:41 ` Jon Steinhart 2022-01-11 20:49 ` Larry McVoy 2022-01-11 21:03 ` Jon Steinhart 2022-01-11 8:50 ` arnold 2022-01-11 14:00 ` Larry McVoy 2022-01-12 23:22 ` [TUHS] troff or groff? (was: Demise of TeX and groff (was: roff(7))) Greg 'groggy' Lehey 2022-01-12 23:29 ` Greg 'groggy' Lehey 2022-01-12 23:32 ` Larry McVoy 2022-01-11 15:47 ` [TUHS] Demise of TeX and groff (was: roff(7)) Clem Cole 2022-01-11 16:55 ` Richard Salz 2022-01-11 18:49 ` Clem Cole 2022-01-11 19:20 ` John Cowan 2022-01-11 20:06 ` Clem Cole 2022-01-11 23:57 ` Warner Losh 2022-01-12 0:03 ` Warner Losh 2022-01-12 8:54 ` arnold 2022-01-12 15:17 ` Clem Cole 2022-01-12 16:33 ` Dan Cross 2022-01-12 18:06 ` [TUHS] *roff history as told to GNU G. Branden Robinson 2022-01-12 18:34 ` Dan Halbert 2022-01-12 22:48 ` Clem Cole 2022-01-12 23:27 ` Charles H. Sauer 2022-01-13 0:35 ` Adam Thornton 2022-01-12 20:01 ` Dan Cross 2022-01-12 22:32 ` Clem Cole 2022-01-13 2:38 ` John Labovitz 2022-01-13 7:42 ` Lars Brinkhoff 2022-01-13 13:47 ` John Labovitz 2022-01-12 8:48 ` [TUHS] Demise of TeX and groff (was: roff(7)) arnold 2022-01-12 15:51 ` Larry McVoy 2022-01-12 15:57 ` Clem Cole 2022-01-12 15:56 ` Clem Cole 2022-01-11 3:22 ` Adam Thornton 2022-01-12 0:32 ` Nemo Nusquam 2022-01-01 20:00 ` [TUHS] roff(7) [ and other related stuff ] Jon Steinhart 2022-01-02 0:12 ` Larry McVoy 2022-01-02 1:04 ` John Cowan 2022-01-02 1:20 ` Larry McVoy 2022-01-02 1:47 ` Steve Nickolas 2022-01-02 2:12 ` Larry McVoy 2022-01-02 3:56 ` Jon Steinhart 2022-01-02 1:48 ` Jon Steinhart 2022-01-02 3:04 ` John Cowan 2022-01-02 3:30 ` Warner Losh 2022-01-01 1:11 ` [TUHS] roff(7) Phil Budne 2022-01-01 1:17 ` Chris Torek 2022-01-01 3:06 ` Larry McVoy 2022-01-01 3:34 ` George Michaelson 2022-01-05 21:15 ` Tony Finch
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