Customer Reviews

Real World Haskell

5 star:		(17)
4 star:		(5)
3 star:		(3)
2 star:		(2)
1 star:		(1)

 

 

The good news is, this is probably the best Haskell book yet. The bad news is, it's still a frustratingly confusing jumble. It starts out well, introducing expressions, type inference, recursion, pattern matching, algebraic types, and higher order functions, with an emphasis on maps and folds (the way real world Haskell code is actually written), and it contains exercises that range from simple to challenging. The first four chapters alone are worth the price.

Unfortunately, the problems start in chapter 5, and rarely let up. It starts by introducing a datatype for JSON data for the purpose of pretty-printing it. The way the pretty-printer is rolled out is confusing -- it constantly jumps between code snippets that won't even compile, because a type they depend on is not defined til nearly the end of the chapter. And while it stays away from excessive cleverness, function names are confusingly named. In fact the entire nature of the pretty-printer revolves around a "Doc" abstraction that is never clearly explained or rationalized.

Later chapters are also rich with useful information, such as explanations of various GHC language extensions to the type system (which are really de facto standard Haskell nowadays). Unfortunately (there are many "unfortunatelys" to use in this review) I would never have been able to follow these explanations had I not already known a little about them -- unlike the rest of the examples in the book, the examples stop being "real-world" and instead devolve into meaningless metasyntax like "Foo" and "Bar".

By the time monads are finally introduced (late, but rightly so -- I consider this delay in introducing them to be a plus), the reader has had to suffer through some very tedious projects, such as parsing an obscure binary format. The book really begins to redeem itself again here, and makes monads clear as a datatype that captures common concepts of encapsulating and sequencing, and completely avoids cutesy visual analogies (no spacesuits or toxic waste here!).

I've not finished the book (I'm still in Chapter 14) but I am eagerly looking forward to its later chapters introducing monad transformers, parallel programming, and software transactional memory. You get a lot of book for the price, but you'll need the support of the always-friendly haskell community on IRC or email to make the most of this tome, or even make any sense of several parts of it.

This is probably the best book on Haskell available.

That said, there were some things I didn't like about it.

The biggest annoyance is that the example in Chapter 12 doesn't actually work. The point is to teach Haskell, not how to read barcodes, but example code that doesn't work just seems sloppy.

I'm also not a big fan of how the code samples are spread out over several pages, with a comment stating which file they belong to. Mostly just a pet peeve, but it does cause some problems because there are a few places where the code references variables or types that haven't been declared yet, so the code won't actually compile until you get further along. Not the end of the world, but the book suggests compiling often to avoid errors and the end of each code snippet would be a natural place to do that.

There are also a few language features that are used but not really explained or used before they're explained. The $ operator, for example, is used on page 165 (among other places), but is only briefly explained on page 248. In that case, even when $ is explained it's incidental to explaining something else (fmap and <$>).

The book is very poorly organized, and for the life of me I can't think of an ideal audience. Some of the material targets beginners, and then the other seventy percent is completely out of reach to all but seasoned pros. The stuff targeting beginners is rather poorly worded -- the book claims no intro to functional programming is required, but the definitions of fold[lr] will send any beginner scrambling to find a decent explanation. The book has a good share of technical rants that serve to do little more than side-track: "Ok, so you've learned foldr, now for good example and test of knowledge I'll tell you it can be written in terms of foldl" -- no further explanation provided. The definitions are all around bothersome. Ultimately, I don't think I learned much at all from this book, and I'd put in the top two worst O'reilly books I've ever read (following CGI Programming with Perl). This book seems to be a really poor mix of these non-existent books: Beginning Haskell, Advanced Haskell, and the Haskell Cookbook -- and with all this said, Haskell comes off as the most difficult language I've attempted to grasp thus far.

I should add I read through this book twice, and didn't learn much the second time around either.

A ton of the book is devoted to a JSON parser, which is rather tiresome. The other "real world examples" are equally poor like a bit-shifting checksum algorithm.

Go read Learn You a Haskell if you're looking to learn the language. If not, you can try this book -- but I'm going to predict your attempt will be fruitless.

Until this book came along you really needed two books to learn Haskell Programming. Haskell: The Craft of Functional Programming (2nd Edition) (International Computer Science Series) teaches the mechanics of Haskell programming, but it can be dry reading. The Haskell School of Expression: Learning Functional Programming through Multimedia shows you the possibilities of Haskell via multimedia programming, but it does miss some basic details about the language that are in the first book. This second book is lots of fun, but I think that the new O'Reilly book replaces the first book entirely and some of the functionality of the second.

Haskell has its roots in academia, and functional programming requires lots of up-front thinking about your total approach. It is not a language where you can usually just sit down and start coding. This book shows you how to use functional programming and Haskell to solve real-world problems. Each chapter contains many code samples, and many contain complete applications. The book contains an application that downloads podcast episodes from the web and stores the history in an SQL database. There is also an application that takes a grainy phone camera photo of the barcode on a book and transforms it into an identifier that you can then ue to query a library website. This is the "fun stuff" that seems to work out so well and so elegantly in the Haskell language.

It is not necessary that you have any prior knowledge of Haskell or functional programming concepts, however general programming concepts are a requirement. This is certainly the first Haskell book to come along in a few years that I would recommend for the novice. As usual with the best of O'Reilly's programming books, this one is well illustrated with lots of well-commented code. The following is the table of contents:

Chapter 1. Getting Started
Chapter 2. Types and Functions
Chapter 3. Defining Types, Streamlining Functions
Chapter 4. Functional Programming
Chapter 5. Writing a Library: Working with JSON Data
Chapter 6. Using Typeclasses
Chapter 7. I/O
Chapter 8. Efficient File Processing, Regular Expressions, and Filename Matching
Chapter 9. I/O Case Study: A Library for Searching the Filesystem
Chapter 10. Code Case Study: Parsing a Binary Data Format
Chapter 11. Testing and Quality Assurance
Chapter 12. Barcode Recognition
Chapter 13. Data Structures
Chapter 14. Monads
Chapter 15. Programming with Monads
Chapter 16. Using Parsec
Chapter 17. Interfacing with C: The FFI
Chapter 18. Monad Transformers
Chapter 19. Error Handling
Chapter 20. Systems Programming in Haskell
Chapter 21. Using Databases
Chapter 22. Extended Example: Web Client Programming
Chapter 23. GUI Programming with gtk2hs
Chapter 24. Concurrent and Multicore Programming
Chapter 25. Profiling and Optimization
Chapter 26. Advanced Library Design: Building a Bloom Filter
Chapter 27. Sockets and Syslog
Chapter 28. Software Transactional Memory
Appendix A. Installing GHC and Haskell Libraries
Section A.1. Installing GHC
Section A.2. Installing Haskell Software
Appendix B. Characters, Strings, and Escaping Rules
Section B.1. Writing Character and String Literals
Section B.2. International Language Support
Section B.3. Escaping Text

I'm a programming amateur mostly looking for fun in programming apart from my job, which requires me also to program. I usually use Python, and I love it. I tried to learn Ocaml or Haskell before but was put off by the books available. This book is really different. It made me love Haskell.

This is a really good book to add to any Haskell programmer's bookshelf. It's also a really good book to help folks get started with Haskell programming if they've ever wanted to journey into the realm of functional programming.

The book covers a lot of topics and some areas I hadn't really thought of using Haskell for (barcode recognition).

Also it's the only Haskell book I know to cover some of the features of GHC (Glasgow Haskell Compiler) and optimization using the tools that come with it.

Does a good job in bringing together many of the stronger features of Haskell.

Haskell is probably one the hardest languages to present because it is so compact and its strength come from leveraging higher level abstractions "on top" of its basic features. With this in mind, this book delivers: it covers all the important features of the language, even the hard ones like monads and it focuses on type class based programming as it provides more haskell specific knowledge than "pure" lambda expression like code.

All books have the challenge to "connect" with their audience to build on a shared environment of knowledge. The book starts with the use of JSON, and brings in topics like binary parsers and directory traversal; these are meant to keep the reader in familiar ground. I cannot criticize the choice of application domains, maybe they made a survey of developers and found these topics as being "most common". They may be of value to you, if not the examples of the book will provide little motivation.

RWH is a solid book that gives the read a good idea of how Haskell works and why its unique. The book has its fault, largely because its a first draft that tries to cover a LOT of material. Don Stewart however has actively tried to aid in any deficiencies found by fixing errors on the web-version of this book so I'm not bothered by errors or things left out in the book.

The biggest complaint people have is that it tends to introduce concepts without really ever mentioning why something is being done. On one hand I agree with that assessment, however I also think that the book was marketed somewhat improperly. I would not call this book a good book for a beginner or your average intermediate programmer. At the very least I would say this book is better suited for experienced programmers or intermediate programmers with a passion for learning about languages.

That said, of the Functional Programming books I own, this is one of the best and most practical. It does not require a doctorate in Denotational Semantics to understand and it does not burn the first half of the book on typed/untyped lambda calculi (not that these things aren't important).

In short, if you want to get down to business working with a functional language, you have some experience with programming and are comfortable with a few errors then this book is for you.

This is one of the best programming books that came out in recent years regardless of language. It covers all the main concepts of the Haskell language and functional programming while at the same time showing how they can be used in real world code. Once past the first few chapters, the examples become non trivial and start to combine multiple concepts to produce short powerful programs, yet remaining totally accessible.

Maybe this is testimony to the conciseness of Haskell language, but to cover the same amount of material the examples cover in another more mainstream language would have taken several more pages if not multiple volumes. How many books cover file processing, regex, parsing, network programming, web programming, system programing, GUI programming and 2 different concurrency mechanisms while teaching a new language all that in around 600 pages. Not many. Above all this book really teaches how to design practical programs in a functional way. An area that was somewhat lacking. So this books might help a broader adoption of FP for real world stuff even if not in Haskell.

The only negatives I could find besides a few typos (It is still a first edition after all) was the usage of the $ operator in examples before it was actually explained. These are minor and don't really take anything away from this book.

Haskell books are in general among the worst I have seen for any programming language, which is really a pity for such an interesting language. I was really excited when I got this book because of all the good reviews, so I thought I would finally understand what a monad is and learn how to make practical programs.

I would like to mention that I have been a C++ programmer, currently work at a research institution, and my main tool at work is now Modelica: I think I am not completely dense and have experience with different programming paradigms, so I suppose my problems may not be limited to me.

Having read The Craft of Functional Programming, I had some background on the first chapters, which sail along nicely on their own; map, filter, fold, partial application and type classes are really nice and well explained.

There are entire chapters dedicated to case studies, in which the authors clearly favoured quantity versus quality: these example chapters are long-winded, nebulous and downright boring. JSON data? Parsers for some godforsaken image format? The authors clearly ignored the basic fact that examples need to be simple to be pedagogical, and lost themselves in details instead. Which would be tolerable if the case-study chapters could be skipped, but new stuff is introduced in these, so one has to follow through.

The coding style is mediocre: as unfortunately common in Haskell textbooks and resources, variables are often identified with single letters, originating cryptic code. It appears that the authors of those code snippets never wrote production code (i.e. code that has to be maintained down the road, possibly by others), given the total lack of semantics; if they did, someone now maintaining their code must be hating their guts. An argument should be named "state", "name", "address", "previous", not "x", "y", "z". In other cases, the choice of function or argument names is plainly misleading, such as in the case of the parser examples.
A terrible quote (approximately): "A SimpleState is actually a state extractor ..." so what about naming it "StateExtractor", instead of ending up with a bunch of misleading function signatures? Were their fingertips hurting, or did they want to save ink?

However, as customary for Haskell documentation, the worst comes with monads. Introduced early because of the IO monad, which is necessary for basic I/O operations, they are however left unexplained until chapter 14, during which time the reader is left to wonder what they are.
The usual foggy buzzwords are then thrown unsystematically around: "side effects" (what side effects could the Maybe data type or lists have? Yet they are monads), "actions", messy function specifications, confusing "examples" that raise more questions than they address.

I tried hard to wrap my brain around these concepts, I read and re-read the relevant chapters at various time over a month, but in the end I threw the book into the recycle bin - at some point I had to cut my losses. I stress this is the first time ever I throw a book away. Well, actually the second, because the first time I threw it away I recovered it because I got a bad conscience about it.

Sorry if I sound bitter, but I am really angry at myself for wasting so much time and effort for a language that will however never be of any practical use. Now, I'll rather learn Python, thankyouverymuch.