[Haskell-cafe] Re: Solution to Thompson's Exercise 4.4

[Sean Perry]

Kaoru Hosokawa wrote:
> Thanks to all the replies!
> 
> It seems that there are ways to solve the exercise if I use constructs
> that are found in later chapters of the book. Sean could be right in
> that some of the exercises are meant to be difficult to solve and they
> prepare you for later chapters.
> 

As a programmer, I was unhappy with my answers to some of the earlier 
exercises because they were clearly inefficient and/or inelegant. This 
kept me reading the book, knowing the answers would present themselves.

On more than one occasion I would fret for a few hours over an exercise 
and then a day or two later learn something new two chapters later which 
  made the exercise much, much easier. Sometimes trivial.

As an aside, I kept all of the exercises in revision control. So I can 
look back at what I first wrote and my later changes. A habit I plan to 
keep as I move on to other programming texts and languages.