Re: Why does man(7) have 3 paragraph macros for the same thing? (was: `\c`, mdoc(7), and man(7) extension macros)

["G. Branden Robinson" <g.branden.robinson@gmail.com>]

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At 2023-10-26T16:58:13+0200, Alejandro Colomar wrote:
> On Thu, Oct 26, 2023 at 09:51:40AM -0500, G. Branden Robinson wrote:
> > At 2023-10-26T16:12:36+0200, Alejandro Colomar wrote:
> > > Regarding PP, LP, and P, what's the history of them?  Why do we
> > > have the 3?  I'm willing to reduce them to just one.
> > 
> > I invite Doug McIlroy to go on record, but my surmise is that they
> > were introduced as crutches for people already familiar with ms(7).
> > 
> > Doug's original man(7) (1979) didn't have `P`.  But Unix System III
> > added it in 1980, and 4.3BSD followed suit in 1986.  This
> > information is in groff_man(7).
> 
> Was the original PP?

It had both `PP` and `LP`.  I reckon Doug figured ms(7) veterans would
have an unreformable habit of typing one or the other.

https://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/man/man7/man.7

I'd have been sterner--and probably less fondly remembered by my peers.

(While I'm armchair quarterbacking Doug's plays of 45 years ago, oh, how
I wish he hadn't have used input traps for anything in man(7).[1])

> Still, compatibility with ms(7) would make it slightly easier to
> trasnfer learning from man(7) to ms(7), would one learn it.  I know
> many other macros are incompatible in bad ways, but the less the
> better, no?

That's true, but these days the knowledge transfer is, I submit, vastly
more likely to go the other way; that is, people will be exposed to
man(7) as their first roff macro language, and might decide to pick up
ms(7).

At that point, they'd have to learn that `LP` and `PP` do _different_
things.  I think it's actually better if they _don't_ have to unlearn
the "fact" (applicable only to man(7)) that they are exactly the same.

Better, I believe, to promote only `P` in man(7).  Anyone wanting to
pick up mm(7) will still enjoy some knowledge transfer.  Without
arguments, `P` in mm(7) "does what you mean".

(I will not elaborate here on what that means; see the groff_mm(7) man
page in groff 1.23.0 and please God not an earlier version.)

Regards,
Branden

[1] In practice, nearly no one took them up for any purpose except the
    one place you _had_ to use them: `TP`.

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