[metapost] turningnumber revisited

laurent at math.toronto.edu laurent at math.toronto.edu
Sat Jul 2 04:26:00 CEST 2011

Hi all,

Jacko writes <Date: Fri, 1 Jul 2011 11:24:03 +0200 (CEST)>

 > So, why the MF algorithm was not compatibly transferred
 > (by John D. Hobby, I guess) to MP? Does anybody know?
 > What's so difficult in transferring MF turningnumber
 > procedure to MP? (I don't suggest that it must be easy,
 > just curious; as I mentioned, I've never understood
 > the sources in detail.)

My hasty reading in Knuth's "The Metafont Book" makes
me think that for turning number and quite a few
other things Knuth makes essential use of bitmaps.
If so, there was no plausible vectorial algorithm
for Hobby to adopt.

On page (vii) I read:

<< The whole story is here in case you're curious. >>

Well, perhaps if one includes the Metafont program's
source and the book "Metafont the Program".

And, in any case, Knuth describes the MF book as a tissue of
lies designed to convey truth and understanding :)

Another important quote from the MF book's introduction:

 << In particular, John Hobby discovered many of the
 algoritnms that have made the new language possible. >>

If we ultimately make some net progress we should
discuss the matter with both Knuth and Hobby.



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