[Haskell wikibook] Splitting of "More on Datatypes"

[Daniel Mlot]

Hi all,

One of the ideas I had while reading the book but didn't have the guts 
to pull off without asking for feedback was splitting the More on 
Datatypes module in Intermediate Haskell. As of now, it has a first part 
which describes an assortment of important datatype techniques 
(enumerations, records and a more formal presentation of parametrized 
types - using Maybe as example) and then moves on to a long discussion 
of binary trees and how to define maps and folds for arbitrary data 
structures. The coupling of these two parts is very loose (the only 
concept of the first part needed for the data structure discussions is 
parametrization) and probably does not justify them being glued together 
to make such a long (27k) module. Another related issue is that one 
important omission from the Beginner's Track is an explanation of 
newtype, and I guess More on Datatypes would be the right place to put 
it. That would make the module even longer, however, and would be 
another reason to make the split.

The only thing I am not sure of is a good name for the second "half" of 
More on Datatypes in case of a split. The obvious choice would be "Trees 
and ???" (I have no idea of a good concise term to replace the ???), 
although maybe something more generic like "Introduction to Data 
Structures" could work.

Thanks, and see you,

Daniel Mlot

P.S.: By the way, Apfelmus has moved Type Declarations to just before 
Pattern Matching. Probably the right thing to do (it just didn't fit 
very well in Haskell Basics), but it will also require some reworking of 
Type Declarations (when I made that module more verbose I envisioned it 
as a preparation for a more general Pattern Matching discussion several 
modules ahead, but with the rearranging the redundancies are probably 
too obvious). I will give it a try soon.