[Haskell-cafe] Re: Rewriting a famous library and using the same name: pros and consf

[Stephen Tetley]

Hi John

My feeling is that a beginner would be transferring almost all of the
the knowledge they gained from Parsec 2.1 if they moved to Parsec 3.0.
We're talking about "famous" libraries, so the library was previously
valuable and useful before the "discontinuous" version change.

In Parsec 3.0's case the discontinuous change revised the parser type
(Parser -> ParserT), the hierarchy for importing modules and where you
find the run functions. These are almost insignificant when an
experienced user wants to move their code from 2.1 to 3.0, but they
may well be significant hurdles for a Haskell beginner working from
examples written with 2.1 (there are no examples in the Parsec 3.0
distribution) or working through the manual.

Daan Leijen's Parsec manual, the QuickCheck paper, Paul Hudak's
Haskore tutorial were all "authored" - it would seem inappropriate to
update them. Of course, a revised project could supply a commentary on
the original documentation - "Parsec - Cliff's notes", detailing where
the differences are, but in practice they don't vis my point that
libraries advance ahead of their documentation.

Best wishes

Stephen