bug#39778: [PATCH] checkdoc: Don't mistake "cf." for sentence end

[Drew Adams <drew.adams@oracle.com>]

> >>> Is "cf." really so much less common?
> >> I think it is, but I won't try to support that as a fact.
> 
> While looking into this, I found Writing for Computer Science by
> (2004) by Justin Zobel.
> 
>     "It is often tempting to use abbreviations such as 'no.', 'i.e.',
>     'e.g.' 'c.f.' and 'w.r.t.'  These save little space on the page,
>     but slow readers down.  It is almost always desirable to expand
>     these abbreviations, to 'number', 'that is', 'for example',
>     'compared with' (or more accurately 'in contrast to', since that
>     is the sense in which 'c.f.' should be used), and 'with respect
>     to', or synonyms of these expressions.  Where such abbreviations
>     are used, the punctuation should be as if the expanded form were
>     used.  Also consider expanding abbreviations such as 'Fig.' and
>     'Alg.' and don't use concoctions such as '1st' or '2nd'.  Months
>     should not be abbreviated.  Make sure that all abbreviations and
>     acronyms are explained when they are first used."  (page 57)
> 
> I think the above points should be carefully considered.

I agree.  Nothing is really gained, and something is
lost, for many readers.

> > FWIW I think "cf." is pretty common.  It also has the advantage
> > of being understood by non-english speaker.
> 
> That's not the case when it comes to speakers of Swedish.  I don't
> know this for a fact, but I'd assume that this abbreviation is more
> common in the Romance languages.

Yes, especially for non-English readers, in general.

Many programmers whose main language is not English
will understand "see also" or "compare".  But how
many will need to look up "cf."?

(But again, reasons to avoid using "cf." are not
reasons not to fix the 2-space bug.  That should
be done, regardless of whether we replace uses of
"cf.")