Re: -ms anomaly

[Ingo Schwarze]

Hi Tadziu,

Tadziu Hoffmann wrote on Fri, Jun 19, 2020 at 03:33:24PM +0200:
> Somebody wrote:

>> Regardless of how the behavior arose, it is certainly a bug
>> for -ms not to implement the semantics intended by eqn.

> My point was that eqn does *not* intend any semantics.
> 
> The Typesetting Mathematics User's Guide says:
> 
>   The .EQ and .EN are copied through untouched; they are not
>   otherwise processed by EQN. This means that you have to take
>   care of things like centering, numbering, and so on yourself.
> 
> and
> 
>   There is also a shorthand notation so in-line expressions
>   like pi sub i sup 2 can be entered without .EQ and .EN.
> 
> I think this makes it clear that although you *can* use EQ/EN
> to visually set off equations from the text (like -ms does),
> it is by no means the only intended usage.

Seconded.

As a practically relevant example, .EQ/.EN generates an in-line
equation in mdoc(7) and man(7) manual pages, i.e. it does not
result in its own indented block of text unless it is surrounded
by something like .Bd or .RS.  Many manual pages rely on that
behaviour.

   $ printf "prefix\n.EQ\ninf\n.EN\nsuffix\n" | mandoc -Tascii
  [...]
  prefix <infinity> suffix
  [...]

Yours,
  Ingo