[Haskell wikibook] Looking for opinions about "More on Lists" (and hello again!)

Daniel Mlot duplode_1 at yahoo.com.br
Wed Apr 4 03:46:09 CEST 2012

Hello everybody,

It has been nearly two years since I wrote a flurry of messages to this 
list, while animatedly copy-editing and restructuring the early parts of 
the Wikibook and, alongside Apfelmus, establishing grand plans for a 
reorganization. Regrettably, the energy I had available to back such 
efforts extinguished itself way too quickly...

Anyway, the book-writing bug has just bitten me again, and so over the 
last few nights I worked towards making the early chapters less 
confusing. Things are far from perfect, but I believe they are now 
easier to follow, both for readers and for any contributors trying to 
figure out what is missing. In particular, as far as I can tell the 
creeping problems with chapters having prerequisites found later in the 
book have now been solved.

Beyond telling you of such developments, I also would like to ask for 
your opinion on a specific chapter. Yesterday I reorganized "More About 
Lists" in an attempt to

1. make it into a coherent story - one which starts with the "obvious" 
recursive doubleList and ends with multiplyList n = map ((*) n);

2. give readers an informal, "en passant" primer on what higher-order 
functions are, without getting down to technicalities; and

3. illustrating why map is so useful, of course.

The problem is that now I look at the finished text and worry that the 
"Generalizing even further" section, which prepares the ground for the 
introduction of map (and where most of the higher-order primer is), is 
now too dense in information for a newbie. It would be perfectly 
feasible to avoid most of the higher-order discussion by, immediately 
after the first "real" paragraph, telling it bluntly that "Haskell 
allows us to make our function more general by passing another function 
as argument" and then going straight into the definition of map. (Such 
an approach, by the way, would be much more in line with Apfelmus' plans 
(documented in the list archives from around May 2010), which is a good 
thing as his plans were coherent and had great potential.)

Summing it up, while I think there is some pedagogical value in my 
current approach to "More About Lists", I have serious doubts on whether 
it would work in practice. So I invite you to skim through it and share 
your thoughts on those issues. Your help will be much appreciated.


Daniel Mlot

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