Higher-Order Perl: Transforming Programs with Programs Paperback – Mar 14 2005
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“It's well written…everyone who claims to be an expert ought to read it…these techniques allow programmers to accomplish far more than they're used to. ―Gregory V. Wilson, Dr. Dobb's Journal, November 2005 “It is, quite simply, one of the best books on programming I have read for a long time.―Martin Schweitzer, Computing Reviews, Association for Computing Machinery, July 2005
“Mark Jason Dominus has hit his mark with Higher Order Perl. It is a very informative book that is a must read for Perl programmers who want to take their skills to the next level. ―Mark Rutz, Linux Journal, November 2005 “The chapter on parsing alone is worth the price of this book. I do not know a better text about parsing in Perl. ―Reinhard Voglmaier, Unix Review, November 2005
“Mark Jason Dominus explores recursion so thoroughly he literally turns it inside-out, showing in simple terms how to turn recursive functions into iterators. ―Peter Scott, President, PSDT, November 2005
“Higher-Order Perl is one of the Perl books that should have a place on the bookshelf of every Perl programmer. It offers an in-depth understanding of important programming techniques and fundamental concepts. Reinhard Voglmaier, UnixReview.com, November 2005
“Higher-Order Perl is a terrific book targeted at the advanced Perl programmer with a significant computer science background. The tone, content, and code make Higher-Order Perl memorable; the knowledge, wisdom, and intuition it provides make it a book any Perl programmer should aim to understand and digest in full.. Teodor Zlatanov, Programmer, Gold Software Systems
The eagerly awaited book by one of the best-known Perl developers summarizing years of innovative practiceSee all Product Description
Most Helpful Customer Reviews on Amazon.com (beta)
You're going to need a completely different shelf for this book.
While discussing caching techniques in Chapter 3, Mark Jason Dominus points out how a large enough increase in power can change the fundamental way you think about a technology. And that's precisely what this entire book does for Perl.
It raids the deepest vaults and highest towers of Computer Science, and transforms the many arcane treasures it finds---recursion, iterators, filters, memoization, partitioning, numerical methods, higher-order functions, currying, cutsorting, grammar-based parsing, lazy evaluation, and constraint programming---into powerful and practical tools for real-world programming tasks: file system interactions, HTML processing, database access, web spidering, typesetting, mail processing, home finance, text outlining, and diagram generation.
Along the way it also scatters smaller (but equally invaluable) gems, like the elegant explanation of the difference between 'scope' and 'duration' in Chapter 3, or the careful exploration of how best to return error flags in Chapter 4. It even has practical tips for Perl evangelists.
Dominus presents even the most complex ideas in simple, comprehensible ways, but never compromises on the precision and attention to detail for which he is so widely and justly admired.
His writing is--as always--lucid, eloquent, witty, and compelling.
Aptly named, this truly is a Perl book of a higher order, and essential reading for every serious Perl programmer.
The book covers recursion (including methods to convert recursive code to iterative code), iterators, streams, memoization, currying, parsing, constraint programming and higher order functions (functions that take functions as arguments and/or return other functions). It is packed with great, sophisticated code which is explained very well and is a model for correct programming. The author takes an approach similar to Peter Norvig's PAIP - advanced coding techniques are presented, and then non-trivial programs are written to demonstrate these concepts.
The comparison with Lisp here is unavoidable, and MJD talks about Lisp in his preface. He claims that Perl shares 6 of the "7 features unique to Lisp" quoted from Norvig's PAIP, and that this basically means that most of what can be written in Lisp can be written in Perl in roughly the same manner. But as he himself admits in a later interview, the 7th "missing feature" of Lisp, namely its uniform syntax, is what *really* differentiates Lisp from the rest. Lisp's syntax allows a very clean handling of higher-order functions, list-processing, and most importantly macros. The contrast between MJD's own code in HOP and Norvig's PAIP code is the best example for this fundamental difference. Be MJD's code as clean and nice as it is (for Perl, anyway), it is nowhere near the sheer aesthetic appeal of Norvig's Lisp.
Still, Lisp is Lisp and Perl is Perl, and each has its respectable place in the world of programming. HOP is a great book to read, and I warmly recommend it to any intermediate+ Perl programmer. For people who have never programmed in Lisp or have never learned functional programming techniques, this book is a must - it will literally take your code to a higher level. For diehard fans of Lisp, this book demonstrates how to employ most of your favorite techniques in the most practical language out there (though the Perlish syntactic sugar will at times make your teeth grind).
Higher Order Perl was originally going to be given some fairly bland name, like "Handbook of Advancted Perl Techniques." This would have been a spot-on (but uninteresting) title. HOP provides the reader with explanation and demonstration of techniques for problem-solving that are often overlooked. The examples are complex and detailed, but not byzantine, and they're built up slowly, piece by piece, so that each line of code's meaning and significance are made clear.
The title "Higher Order Perl" refers to the book's most central technique, functional programming. While many programmers understand how to abstract a specific solution into a more general one, Dominus helps the reader learn to push the envelope, abstracing generic solutions into extremely generalized solutions that can be applied to seemingly-unrelated problems. This is frequently done by the construction of functions that build functions that build functions -- and so on, functions all the way down. Instead of solving the problem in base, earthly Perl, the programmer produces Perl elements of a higher order which, operating in harmony, become all things to all people.Well, I'm hyperbolizing, but I think it would be hard for me to over-emphasize the value of techniques like closures, iterators, and currying. They are, in part, what make Lisp so powerful, and the marriage of Lisp's power and Perl's expressivity is a happy one.As for the writing, it is good. The language is clear and the material is well-presented. One should be cautioned, though, that the book is dense. Dominus is constantly pressing onward, explaining new techniques or new ways to apply already-explained techniques. I found myself reading each page carefully and deliberately, only to turn back to it a few pages later, to be sure that I understood how the new material was relying on the old. It made the book a challenge to read, but it was a thoroughly enjoyable challenge. I never felt so frustrated by a bizarre idea that I gave up or so bored with an over-explained one that I skipped ahead.
Finally, while the techniques that Dominus presents are powerful and advanced, the required knowledge of Perl is not particularly great. Because he clearly explains the key Perl concepts that he uses (especially closures and associated scoping issues), any competent programmer with a working knowledge of Perl should be able to put the ideas in Higher Order Perl to work.
For serious Perl programmers, Higher Order Perl is a must-read book.
HOP gives an easy access to Functional Programming for Perl developers. The book is written in a personal manner and is fun to read and sometimes even funny. It is definitely not a dry factoid book.
The examples in the book are useful not only as they demonstrate nicely the need and power of functional programming but also due to their practicality for seasoned programmers.
I felt the influence of books such as "Structure and Interpretation of Computer Programs" by Abelson and the Sussmans" on HOP, and it was very nice and helpful to read MJD's recommendations for other good readings on the subject.
I got to reading HOP cover to cover, several times. I attempted to solve myself the problems raised in the book and found the process of doing that enjoying and rewarding. Reading on the commentary and approach suggested by MJD was in many ways enlightening. You can find some very amusing footnotes in the book that makes it yet more fun to read.
MJD gives a refreshing view on Perl programming, and shows that tasks that can be very complicated and hard, or computationally intense can be turned "inside out" and handled in a functional programming approach that simplifies understanding, simplifies the solution and also simplifies the implementation.
MJD presents a very useful introduction to functional programming using Perl using practical problems, and the nice thing is that even theoretical problems get practical usages when explained, which makes the reading fun, and worth the while for the non-theoretical people amongst the readers.
Though the book sometimes goes into detail or length too much for my taste, it does do a good job in giving the new view of the capabilities of a Perl programmer and the Perl programming language and how to use them.
I can testify that a lot of code that I got to see, write and maintain got a considerable "lift" and "upgrade" since me and other colleagues of mine read this book and used some of the wisdom that it offers.
There are many good and useful follow-ups to this book in the form of Perl modules on CPAN, articles and posts on the web and some book chapters. Look them up!
Also, if you feel that this functional programming approach is useful to you, you might want to probe further on this by reading Haskell, Lisp, Scheme (and other functional programming languages) literature. There are several "must read!" for these programming languages that will give you a very deep understanding and good skills in this programming paradigm. Also -- you will find, especially after reading HOP, that you now have the tools to easily and practically apply the functional programming principles that you learn in Functional Programming books to Perl and use it in your Perl code.
A few words on MDJ himself: I read a lot of what he wrote for Perl and used some of his modules and code that is available on the web. I had the pleasure of hosting him on the first YAPC in Israel and attend a 3 day course that he gave. He is a very smart person, a very nice person and an excellent teacher and a very good writer. If you don't already know MJD, this book is a very good way of getting access to some of the wisdom that this gut has to offer.
If you don't know which Perl books to buy and/or to read, know this: HOP is one of the books that you should read!
(It is funny that almost 3 years after I read this book for the first time and after reading some of the material before editing, as MJD offered in his private mailing list, I only now get to write a review on it. But still, it surely deserves a book review and a good mark too.)
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