Re: [PATCH v1 1/2] [troff]: Add lengthof() macro.

[G. Branden Robinson]

At 2023-08-04T03:00:10+0200, Alejandro Colomar wrote:
> *  src/roff/troff/env.cpp (lengthof): Add macro to calculate the number
>    of elements in an array.  It's named after the proposal to ISO C,
>    _Lengthof(), which wasn't accepted for C23, but hopefully will be
>    added in a future revision.
[...]
> I added it there because I didn't find a "common utilities" header
> file.  Please suggest a better place.

As I understand it, it is not idiomatic C++ to rely on the preprocessor
any more than is necessary--and that means, again AIUI, to interpolate
the text of header files and interface with C code.

Yes, groff does use the preprocessor intensely in a couple of places.

https://git.savannah.gnu.org/cgit/groff.git/tree/src/include/itable.h?h=1.23.0
https://git.savannah.gnu.org/cgit/groff.git/tree/src/include/ptable.h?h=1.23.0

That is because C++ didn't have templates, or they weren't yet mature[1]
when James Clark wrote this stuff.

And I recognize that "cultivation of robust and flourishing macros" _is_
(or can be) idiomatic C, as Ben Klemens champions.

groff is stuck in a very hard place.  People have lots of excuses to not
hack on it.

1.  From C programmers: "Eww! It's in C++!"
2.  From C++ programmers (1): "Eww!  It's not in C++23 already!  How can
    you not be using all the latest features?  What a bunch of losers!"
3.  From people generally: "Why care about groff?  Or text formatting?
    I want my Markdown documents in angry fruit salad colors on my
    JavaScript terminal emulator!"
4.  From C++ programmers (2): "Wow, this pre-standard dialect is about
    as mind-twisting to current practicioners as an exhibit of
    pre-Typesetter C[1] (attached) is to C programmers."

I don't think coders in the first three categories can ever be won over
short of a ground-up rewrite.  That _would_ be a cool project, and it's
one Ralph Corderoy tried to get me to do (possibly so I'd stop posting
to this mailing list).  But I kind of like working on code that people
other than me are actually using.

At 2023-08-04T03:00:12+0200, Alejandro Colomar wrote:
> *  src/roff/troff/env.cpp (is_family_valid): The old code was
>    eyeball-bleeding.  This cuts 6 lines to 3, and each of them is
>    significantly simpler to read.  Remove the comments of how it could
>    be improved using modern C++, as I don't think it would improve much
>    vs this C implementation.
[...]
> I need a new pair of eyeballs.  They bleeded so much!

Yeah, who's responsible for this crap?

39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1259) bool is_family_valid(const char *fam)
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1260) {
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1261)   // std::vector<const char *> styles{"R", "I", "B", "BI"}; // C++11
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1262)   const size_t nstyles = 4;
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1263)   const char *st[nstyles] = { "R", "I", "B", "BI" };
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1264)   std::vector<const char *> styles(st, (st + nstyles));
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1265)   // for (auto style : styles) // C++11
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1266)   std::vector<const char *>::iterator style;
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1267)   for (style = styles.begin(); style != styles.end(); style++)
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1268)     if (!check_font(fam, *style))
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1269)       return false;
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1270)   return true;
39ffa368dc src/roff/troff/env.cpp (G. Branden Robinson  2023-05-25 05:35:25 
-0500 1271) }

This is a relatively new function, and all my fault.  I wrote it because
validation of font families wasn't being done previously.

https://savannah.gnu.org/bugs/index.php?64155

In my defense, I seem to remember modeling it on an example in Lippman's
_Essential C++_, which documents C++98.  I figured he was an expert.
Bad choice?

Lippman never updated that book for any later version of C++, and I
don't know why.  Maybe everybody else decided his code was horrible.
Or maybe he got off the C++ train before Scott Meyers did.[2]

But I put those C++11 comments in there because the C++98 way of doing
things seemed incredibly gross, and I had trouble believing that C++
programmers subjected themselves to it.  They did, and they didn't like
it, but it took 13 years to get a remedy because, by God, _someone_ had
to have "concepts" in the next version of language.[3]

Therefore--please take another crack at it without using the
preprocessor, if you'd like.

Regards,
Branden

[1] "Still aren't!" <drum fill>
[2] https://scottmeyers.blogspot.com/2015/12/good-to-go.html
[3] And failed to do so.  But I'm sure it pitches brilliantly in any
    conference room.  All you have to do is stand up in front of a
    whiteboard, put your elbows to your waist while extending your
    forearms at a 45 degree angle in the plane parallel to the floor,
    with palms facing up, gravely intone the word "concepts", and take
    your seat.  Boom!  Instant buy-in!  Steve Jobs himself could not
    have sold it better.

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