Would have expected more | Pro Perl Parsing (Pro)

A bit disappointing | Pro Perl Parsing (Pro) | Christopher M. Frenz

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	• Pro Perl Parsing (Pro) Christopher M. Frenz Apress, 2005 - 272 pages average customer review:based on 8 reviews view larger image
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highly recommended

Excellent introduction

This is one of the easiest to take in and most informative books I've come across for a while. I freely admit to not being a Perl guru. I generally don't know ten different ways to perform a specific action in Perl - let alone have ideas on which way is best. But I use Perl daily to make my life easier. A big part of that is parsing information - in HTML, XML, from the command line output of tools and applications and from files and logs. Pro Perl Parsing pulled together and made much clearer many of my own hastily learnt techniques and processes, taught me some new ones and explained some of the odd results I've gotten in the past. The only criticism of the book is that it wasn't long enough - I'd love to see a 2nd Edition with a greater focus on parsing command line, configuration files and other 'administrative' style activities - it's not just programmers who parse. :)

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Would have expected more

The first 108 pages of "Pro Perl Parsing" deal with basic parsing concepts and give examples on how to use a CPAN module to define parsers. It's not quite accurate at times, though: The author uses the terms 'precedence' and 'associativity' interchangably, although these are orthogonal concepts. And the parser on page 82 has a design flaw (hint: try parsing "(5*(3+4))+1)", which yields 40, ouch!).

Then come 30 pages with a manual-page style explanation of Damian Conway's Parse::RecDescent module, along with some interesting tidbits here and there.

However, I would have expected to read a better explanation of the underlying parsing theory, like a distilled and simplified version of the "Dragon" book (Aho, "Compilers"). I would have liked to read how to write a custom parser from scratch in Perl, like in Mark Jason Dominus' "Higher Order Perl". Also, I would have expected more practical examples on how to tackle common parsing problems.

However, the second half of the book starts with an explanation of the HTML language. We get to know how titles and lists and links are done in HTML. Then we learn how to fetch web pages with Perl. Also, we learn about web services via SOAP and XML-RPC, about formatting output in Perl and are getting a chapter on "data mining". These topics aren't related to "parsing" at all, though.

There's an example on page 202 on how to parse command line arguments by lumping them all together to form a single string and then firing up an expensive recursive descent parser to tear them apart. Experienced Perl programmers would solve this common problem elegantly in a single line of Perl, using the Getopt::Std module.

So, I'm somewhat ambivalent on this book. Since there's not many books on Perl parsing, I was excited about it, but I was somewhat disappointed by the lack of depth, accuracy, and the filler-style second half of the book. I would have liked to read more about parsing in Perl and less about how to use CPAN modules dealing with parsing-related topics. Had the book maintained a strong focus on plain "parsing", it could have been a slam-dunk five-star. So, it's only three -- worth reading, but not a potential classic.

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A bit disappointing

Well, not was I was looking for. I would like to find something more than a description of what modules do, and that's mostly what it does. The last chapter is a smorgasbord of light descriptions of modules such as Text::Balanced, which have little or nothing to do with parsing, or with pro, and the chapter on XML processing looks like just a filler with little to add to the rest of the book or to the literature on XML+Perl.

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Experts guide to extracting the data you want!

Christopher M. Frenz has put together a real how to manual for those who use Perl for parsing.
Grabbing the data you want from a file can be tricky but Frenz has taken parsing from the top shelf
and placed it where any Perl programmer can use it.

The opening chapter is great for anyone who has had trouble understanding how to use the regular expressions
as built into Perl. He explains Pattern Matching, Quantifiers, and how not to be Greedy with your pattern matching.
However, the book goes far beyond the basics of regular expressions in Perl to various libraries which can be used
for parsing HTML, XML, RSS, and any text based file.

Chapter 2 of the book seems very heady as he discusses the use of Generative Grammars which is foundational
for anyone wanting to truly understand parsing. From Chomsky's grammar to Type 1, 2, and 3 grammars,
he details these structures and how to use them.

Perl modules GraphViz::Regex, Regexp::Common, Parse::Yapp, Parse::RecDescent, HTML::TreeBuilder,
XML::LibXML, XML::SAX, and XML::RSS are all discussed in this book and clear examples are given on how
you can use them to parse files to get the data you want.

In the end of the book is a section on Data Mining well worth the read dealing with Descriptive Modeling and
Predictive Modeling. For anyone doing data mining work from Web based data or from Relational Databases
this section can be very helpful.

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Very techincal but just what I was looking for

Wow! I do a lot of data parsing and this book is one of the best finds I have ever made. I should point out, however, that it is not for the average reader. This book is very technical in nature but absolutely fabulous if you are technically inclined or already proficient in Perl or have some experience parsing using another language. It seems that I am always finding strange problems that create a need to parse large amounts of data to extract only the relevant information and present it in a usable form. Author Christopher M. Frenz covers the whole gamut of parsing and does so in a very logical progressive manner. First he starts with the use of regular expressions and does a great job including some complex example of just what can be done. From there he moves to generative grammars and how they can be used to determine relevant data of interest within a text, XML or similar file. Then from there he builds on your understanding by discussing specialized modules that can be added to your Perl implementation and how they are used. And, of course, he discusses data mining and how to efficiently use this information. This is an excellent technical book that is a required resource for anyone using Perl to parse documents. Pro Perl Parsing is highly recommended.

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I thoroughly enjoyed this...I write and maintain a fair amount of Perl, and matching and parsing patterns is often the largest part of the work.

? A.P. Lawrence, Information and Resources for Unix and Linux Systems

Perl, one of the world's most diffuse programming languages, was born out of the need to resolve the creator's dissatisfaction with what were at the time standard data-parsing solutions. Indeed, since the 1.0 release in 1987, Perl has been heralded for its powerful parsing capabilitiesfeatures that are further enhanced through the thousands of Perl extensions made available through CPAN (the Comprehensive Perl Archive Network).

Pro Perl Parsing begins with several chapters devoted to key parsing principles, discussing topics pertinent to regular expressions, parsing grammars, and parsing techniques. This material sets the stage for later chapters, which introduce numerous and powerful CPAN parsing modules, and provide an ample supply of example applications.

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