[Haskell wikibook] More on topic reorganization

[Daniel Mlot]

Hello,

Just to mention I have added some ideas for "Elementary" and 
"Intermediate" in the list of topics as well. Alongside some other 
issues, there are three things for which I can't see an obvious solution.

* Can we provide meaningful examples of pattern matching on lists 
without making use of recursive algorithms? At first I the possibility 
of moving the "Recursion" chapter to Basics, just after "Tuples and 
Lists", and use the context to introduce x:xs - but that would kind of 
defeat the pedagogical proposal of emphasizing function composition 
before considering in more depth the "inner workings" of functions. The 
most adequate alternative, then, would be to mention pattern matching on 
lists only *very* briefly, I guess...

(A related observation. Apfelmus' proposal includes a "Working with 
lists" module in Basics which would be dedicated entirely to list 
comprehensions. Initially I wondered whether discussing map and filter 
in that context would be an improvement. Doing so, however, would 
immediately make it necessary to push, at the very least, "Recursion" to 
Basics as a prerequisite. Having both map, filter and recursion in 
Basics would likely make things too clunky. I also wonder if this 
decision on how far to delve into lists in Basics would have any 
significant effects in the "Building a Vocabulary" module.)

* I am slightly bothered by having "More on Functions" and "Control 
Structures" only at the end of "Elementary Haskell". "Control 
Structures" should probably be after "Pattern Matching" anyway, even 
more so now that we're presenting case structures for the first time. As 
for "More on Functions", I feel moving it to an earlier point (just 
after "Recursion", maybe) could improve reading flow (IMO increased 
alternation of "syntactic" and "conceptual" modules makes for a less 
tiring read). Furthermore, it would allow us to make occasional use of 
lambdas, prefixed operators and similar things in the following chapters 
without worrying with pre-requisites (and, at the same time, helping 
readers to, through small doses, get used to the syntactic variants).

Regards,
Daniel Mlot

P.S.: Apfelmus: Nice thought to have added examples to the cheat sheets. 
I only fear they can grow a bit too wide sometimes, but in such cases 
nothing stops us from putting a "see on the detailed explanation" note 
there :)