Further reading
As we said at the very beginning, this manual is not intended as a
tutorial on either functional programming in general, or Haskell in
particular. For these things, our first recommendations would be for
the Introduction to Functional Programming by Bird
and Wadler [7], and the Gentle Introduction to Haskell by
Hudak, Peterson and Fasel [8], respectively. Note,
however, that there are several other good textbooks dealing either
with Haskell or related languages.
For those with an interest in the implementation of Hugs, the
report about the implementation of Gofer [9],
Hugs' predecessor, should be a useful starting point.