Perl Best Practices 288
honestpuck (Tony Williams) writes "I have to admit that I can bristle at books that try to preach, so Perl Best Practices was on a hiding to nothing when I came to review it. I also have to admit to being torn about the author -- after all, he is one of those poor fools who insist on living in cold, unenlightened Melbourne, while I live in vastly superior Sydney. On the other hand, how can I dislike a man who manages to place a quote that involves my favourite character, Lady Bracknell. from my favourite comic play, 'The Importance of Being Earnest,' in the first few pages of his book?" Read on for Williams' review.
| Perl Best Practices | |
| author | Damian Conway |
| pages | 492 |
| publisher | O'Reilly Media |
| rating | 8 |
| reviewer | Tony Williams |
| ISBN | 0596001738 |
| summary | Methods of coding to improve your Perl software |
Many years ago I read a marvelous article that explained why so may early editors and word processors supported the keyboard commands of WordStar. When it's first born, a baby duck can be easily convinced that almost anything is its mother. The small bird imprints, and it takes a lot to shift its focus. "Baby Duck Syndrome" affects programmers in a number of ways, not just their choice of editor, and Conway is walking right into the middle and arguing with your imprinting on almost every page. A brave man; fortunately he has the street cred to make you at least listen.
So I carefully placed my bias and bigotry in the bottom drawer and prepared myself. I discovered a well-written, informed and engaging book that covers a number of methods (hey, 256 rules, come on Derrick, 2 ^ 8 rules can't be a coincidence!) for improving your Perl software when working in a team. That means all of us when you remember an adage a guru once told me: "Every piece of computer software, no matter how small, involves at least a team of two -- me, and me six months from now when I have to fix it." Conway puts it differently "Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live."
The first chapter outlines the why and where of the book. The why is to improve your code with three goals; robustness, efficiency and maintainability. The chapter finishes with a short exhortation to us to "rehabit." Don't like the word much but I applaud the aim.
Conway is far from timid. He jumps right in to the deep end of the wars, with formatting the appearance of your code. I thought the chapter was brilliantly written until he told me I shouldn't "cuddle else statements," at which point I realized what an ill-informed idiot he was. Oh, hang on. Hey, that almost makes sense. OK, that's a cogent argument for your point of view, Conway. I also have to admit that earlier you did say that your rules for this bit weren't gospel, that if you wanted a variation that was OK, just have a standard and make sure you can support it with a code prettier. Perhaps not a total idiot after all.
After successfully negotiating those shark infested waters, Conway -- obviously a man who knows no fear -- wades into naming conventions. Once again he gives coherent arguments, pointed examples and counterexamples. It all makes sense.
The book's page at O'Reilly has an example chapter and a good description, but no table of contents so here's a quick list of the headings:
- Best Practices
- Code Layout
- Naming Conventions
- Values and Expressions
- Variables
- Control Structures
- Documentation
- Built-in Functions
- Subroutines
- I/O
- References
- Regular Expressions
- Error Handling
- Command-Line Processing
- Objects
- Class Hierarchies
- Modules
- Testing and Debugging
- Miscellanea
The book is also well-written and well-edited. The order of topics covered is a sensible one, and the book is appropriately structured. It reads and feels as if you are being given the wisdom from many a hard-won battle coding and maintaining Perl code.
My one complaint is that I found it dry: you are reading through pages of argument and examples without much relief. Perhaps this book might be best digested in a number of chunks, making the effort to use the ideas from each chunk for a while before moving on to the next.
Every so often I read a book from O'Reilly that makes me fear that they are slipping, then along comes a book like Perl Best Practices, and I'm reminded that when it comes to Perl, O'Reilly authors wrote the book. Once you've rushed through Larry's book and learnt the finer points with Schwartz and Phoenix's 'Learning' titles, you may well find that this is the perfect volume to complete your Perl education. If you believe your Perl education is complete, then buy this volume and I'm sure you'll find a lesson or two for yourself.
This book is not really aimed at the occasional Perl programmer (though many of us would probably benefit from its wisdom), but at the person who is professionally programming in Perl and wants to produce better quality, more easily maintained code. For this person Perl Best Practices is a 9/10. For the rest of us, the 'rehabiting' process might be a little too arduous; personally, I'm going to pick a few of the chapters and work on those for a while, maybe naming conventions and variables. For me I'll give it an 8.
You can purchase Perl Best Practices from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Smile (Score:4, Funny)
Re:Smile (Score:5, Funny)
Try not to let my sig scare you too much.
Characters per line (Score:4, Funny)
Re:Characters per line (Score:3, Funny)
Re:Characters per line (Score:3, Funny)
Re:Best Best Practice: Don't Bloat Perl (Score:5, Insightful)
That a joke? I don't think there's any language that can be fully understood after a 2-semester course.
Re:Best Best Practice: Don't Bloat Perl (Score:3, Funny)
Re:Best Best Practice: Don't Bloat Perl (Score:3, Insightful)
In other words, if all you know is the syntax, you don't know the language.
Re:Best Best Practice: Don't Bloat Perl (Score:2)
Any of the LISP's are simple. Ruby tends to be simple too. Now, if you are including in that 2 semester course the libraries as well, then you might be correct, but there are plenty of examples of very simple, orthogonal languages.
Re:Best Best Practice: Don't Bloat Perl (Score:3, Funny)
I disagree. Most people I know are able to completely master pig latin with just a couple of days of study and use.
Re:Best Best Practice: Don't Bloat Perl (Score:2)
You've obviously never met Larry Wall. You, sir, are no Larry Wall.
People (well, some people) love C for its simplicity, and people (some people, maybe some overlap with the previous group, maybe not) love Perl 5... but I
Re:Best Best Practice: Don't Bloat Perl (Score:4, Insightful)
Perl's syntax is very complex; it has a lot of operators and provides many different ways to do the same thing. This makes reading other people's code very difficult.
Everyone starts by learning a subset of the language, then building upon that by learning more after they've mastered the basics. You can write a lot of perl code without knowing half the syntax. The problem is, since everyone learns a different subset, reading someone else's code is impossible for a beginner, and unfamiliar syntax isn't something you can easily look up in a reference. A language like PHP has a simpler syntax and far fewer operators, and makes up for it by having a large number of functions; once you've got the syntax down, you can just look up unfamiliar functions in the documentation and figure out what's going on. The result of this is that PHP looks easier to beginners while Perl looks daunting.
I'm completely ignoring Perl 6, and I'd advise others to do the same for at least a few more years.
Re:Best Best Practice: Don't Bloat Perl (Score:4, Informative)
As someone who regularly downloads and fixes broken perl modules, I have to disagree.
Everyone tends to use the same subset at the start.
The big thing you see in a beginner's code are just control structures (especially foreach statements), and regular expressions (and then mostly only stuff you'll see in an awk expression).
Things like inventing a new inheritance structure (as is done by Class::DBI, OOTools, and PDF::Template), embedding a LALR parser (all the template engines), are a sign of a mature coder, and happen much less. These people are more likely to write code in a logically consistent, well designed manner such that it is easy to extend.
So far I've found one module that I tried to fix (and ended up not because it was too much work) that wasn't either simple or well designed (Class::DBI::FormBuilder).
Obligatory joke (Score:3, Funny)
Perl Best Practices, page 1.
Use Python.
Ba-dump-bump! Thanks, I'll be here all week. Be sure to tip your waitresses.
Re:Obligatory joke (Score:3, Funny)
Use Ruby.
Ba-hiss-hiss-hiss! Good bye you slimey snake.
Syntax problem (Score:5, Funny)
use Python;
Re:Obligatory joke (Score:4, Insightful)
It's funny you bring it up, because here are my impressions of the book:
It's really quite a good book. There are probably only two or three things I actually disagree with Conway on, and for a book that takes stands, that's immense. He even convinced me on the "inside-out" class approach, which I scoffed at when I first heard about it.
The sad fact is, that if you follow all these practices, that's as good as Perl's going to get. And it's not very good. After using Ruby, or a good functional language, for a while, going back to Perl is like... well, it's not like visiting an old friend. It's like having to get back in your old jalopy because someone stole your "good" car.
By showing us how good Perl can be, Conway shows us the limit of its quality. Once upon a time, this would be an exciting lesson (I wrote programs in Perl almost exclusively for years, and loved it). But now, it just shows how much of a papering-over it needs to seem competent.
I like Ruby a lot. I like Erlang a lot. I wrote a lot of Python code on a huge project that used it exclusively; it has its charms, and is better than Perl, but its irritations as well ("char".join(array)? please). I'm not going to pick "the next big thing" except I will say that, for me at least, it's not Python.
#1 Perl Best Practice (Score:5, Insightful)
Ofcourse if you're using Perl4 and below, you're out of luck...
Re:Watch out for the SOAP... (Score:2)
Python forces you to structure your code in a certain way, which makes it readable and maintainable in large projects. However, Perl doesn't in any way prevent you from writing readable and maintainable code - Perl just doesn't force you to write in a particular way, so it's up to you to implement self-imposed rules.
Buzzkill (Score:5, Funny)
What's the point of using Perl if your code suddenly becomes intelligible? After all, there is more than one way to obfuscate it.
Re:Buzzkill (Score:2)
And it's possible to obfuscate crap in any language -- the problem is that there are just so many bad programmers who have written Perl. I'm guessing there are equally bad Visual Basic programmers to Matt Wright, but they're just not as infamous, as they didn't decide to share out their inintended malware for people to learn from.
Re:Buzzkill (Score:2)
Indeed, the language positively encourages unreadability, but if you are stubbornly determined to write readable Perl, it is possible.
Yeah, but at least some languages try to encourage readability, Perl is obfuscated by default.
Re:Buzzkill (Score:3, Insightful)
This is exactly right. Perl doesn't force (or even encourage) you to write code in any particular style; it gives you a great deal of flexibility. If you want to write good clean maintainable code, you can; if you want to write something that looks like my sig, you can. The strict pragma will add certain restrictions to prevent you from doing particularly awful things (l
Re:Buzzkill (Score:2)
The grandparent needs to spend more time with http://thedailywtf.com/ [thedailywtf.com]. I almost never see perl code, but I see bizarre coding every day.
Best Practice? (Score:2, Funny)
Re:Best Practice? (Score:5, Funny)
Re:Best Practice? (Score:2)
Ay mate? (Score:3, Funny)
Oh, you do slay me, mate.
Is this like http://slashdot.co.au/ [slashdot.co.au] or something?
This holds true (Score:5, Funny)
Re:This holds true (Score:2)
Re:This holds true (Score:2)
Re:This holds true (Score:2)
Re:This holds true (Score:2)
Re:This holds true (Score:4, Insightful)
Perl's syntax is very complex and it has a lot of operators. Most people don't know all of Perl's syntax, they only know a subset. However, each person knows a different subset of the language, so if you try to read code written by someone else who knows parts of the syntax you haven't learned yet, it won't make sense and you may not even be able to look it up in a reference to figure out what's going - it's easy to look up functions, but if you don't know what @foo[5..10] means, you may not know where to find out.
coding style (Score:2, Insightful)
ok (Score:2)
and use strict
But really, if you want fancy error-catching technology you'll have to wait until Perl 6.
Short article by the same author (Score:3, Informative)
In a similar vein there was a recent article by the same author printed on perl.com:
Re:Short article by the same author (Score:2)
"The following ten tips come from Perl Best Practices, a new book of Perl coding and development guidelines by Damian Conway."
It's an excellent article, and those ten tips are good ideas no matter what language you code in.
own the book (Score:5, Informative)
One nice feature I found was the chapter on formatting included vim and emacs config snippets to achieve the same effect, as well as the config file to use perltidy to do the same thing.
I agree it is dry, and it's very "bam bam bam" with the examples. Not something you can read start to finish. you'll want to try implementing things right away. I suggest taking the book a chapter at a time and implementing the changes in your code then.
There were some bits I agreed with, and some I didn't agree with; however the parts that I didn't agree with they explained in a reasoned and rational manner, and made me rethink my own thoughts on the subject.
I've recently fallen into the position where I'll be leading possibly two other developers- this book will become a standardization format for our company.
again, I highly recommend this book.
-morgajel
Dumb review (Score:3, Insightful)
cuddling? (Score:2)
Re:cuddling? (Score:2, Informative)
"Cuddling" else means doing this:
instead of this:
Re:cuddling? (Score:4, Informative)
Re:cuddling? (Score:3, Informative)
} else {
Uncuddled:
}
else {
or
}
else
}
(Suitably indented of course.)
Best Practices (Score:5, Insightful)
1) There are reasons to use Perl. Nothing REQUIRING it, granted, but that's true of any language. Python and Ruby inhabit similar but not identical niches.
2) Line noise reputation aside, Perl can be _very_ readable. Concise done correctly means that it says what it does and does it, without unnecessary compiler syntax effort. Concise done wrong means it's not obvious what you are doing. Perl gives you enough rope to hang yourself...kind of like computers, and open source in general.
3) As far as the book goes, I was eager to get my hands on it and learn, but worried that I'd find it too limiting and restrictive. The tips ranged from the obvious (strict and warnings), the non-syntactical useful (use code and documentation template for new projects), to the small but fascinating (make your hash names end it words like "for" or "of", so that normal usage is self documenting: $name_of{$user} ). Very few of the tips did I disagree with, and even though the book talks about the importance of HAVING standard practices over what those practices are, I'm moving my dept to adopting the standards in the book because my preference is often habit over any calculated reason.
Perhaps 50% of the tips have nothing or little to do with Perl and everything to do with programming, programmers, or users.
This is not a life altering book. It is, however, a high quality book with some very good tips.
Re:Best Practices (Score:3, Insightful)
I tell you what turned me away from Perl, though: the syntax for complex data structures was never clean enough that I could remember it from session to session. The python for getting a hash of arrays (in Perlspeak):
Perl made it possible, but Python made it easy. What about returning complex objects from functions? [1]
Re:Best Practices (Score:4, Informative)
$a = { first => [ 1,2,3 ], second => [ 4,5,6 ] }
print $a{first}[2];
And...
sub foo { return { first => [ 1,2,3 ], second => [ 4,5,6 ] } }
print foo()->{first}[2];
One place where Perl syntax really suffers is dereferencing nested structures though. Consider
@array = @{ $hash{$key} };
Blegh.
Re:Best Practices (Score:3, Informative)
Bull.
Looks easy enough to me. Damn near identical even.
Ditto. In modern perls the arrows tracing the path in the data structure are even optional (however code without them is as ugly as Python IMHO :-P)
Re:Best Practices (Score:4, Informative)
or
In fact, as far as I can see, the code is basically identical.
Read It (Score:2, Informative)
It's nice to have, and it gives me things to think about for improving code, but it's by no means essential.
In some cases, the author's advice is inconsistent. For example, he sometimes suggests that a programmer avoid constructs that would force a reader to look something up. And some other times, he suggests using a construct (e.g., \A and \z instead of $ and ^, respectively, in regular expres
Re:Read It (Score:2, Funny)
They were given away to OSCON attendees... (Score:4, Insightful)
I get a copy for every new dev now. I'm not going to force them to use all of it, but it definitely makes them think when they start working on larger projects.
I'd also recommend MJD's Higher Order Perl if you want to go even deeper.
I always think it's funny when people argue heavily about hating to work to a "best practices" style. And then start agruments about how crap Perl is because it's unreadable. Anyway - I digress.
cLive
Sad comments on a great book (Score:4, Insightful)
More to the point, you will write crap in any language if you don't understand the conventions, idioms, and best practices of the language.
Perl is a lot like Lisp. You need to think in terms of lists before you see anything but the sigils and you tend to write "C in Perl". Further, until you see *good* Perl code, it's hard to know any better. Before this book, the book I'd refer people to was "Effective Perl Programming" by Hall & Schwartz. The goal was to get beyond "baby talk" and use the language well.
I'm about 130 pages into "Best Practices" and I like the book a lot. It's definately on the required reading list for any Perl programmers that we hire.
I can't say I agree with Damian about *all* the conventions (I really *like* "unless") but I agree with most of them, and having met him once, I'll admit that he knows more about Perl than I'm ever going to know, and more about computing languages and PROGRAMMING best practices than most of the people that have responded to this topic.
If you code in Perl often enough that you wish your code was better, you should pick up this book.
Perl Tip of the Day (Score:2, Interesting)
Anyway, last week my mom told me it was important for me to start giving back to society, so here is your Perl tip of the day. It took me a few months of writing awful, inefficient reg
Re:Perl Tip of the Day (Score:4, Informative)
wrong. ? makes the sub-expression lazy/non-greedy.
Read Jeff Friedl's Mastering Regular Expressions.
Perl Best Practices (Score:4, Funny)
DDJ and Baby Ducks (Score:2)
Re:Wordstar keybindings (Score:5, Interesting)
I grant you, left-handers and non-QWERTY keyboarders are left out in the cold, but at least there was a method to the madness.
Non-QWERTY (Score:2)
Pity it's so much effort to change the bindings in most word processors.
Re:Wordstar keybindings (Score:2, Funny)
Re:Wordstar keybindings (Score:2)
Re:Wordstar keybindings (Score:2)
Left hand is more useful in Qwerty (Score:3, Interesting)
In the Qwerty layout, more of the most commonly-used letters are located under the left hand. Taking the limit as T, G, B, you can hit about 57% of letters by frequency. If you include occasional jumps as far as U, J, N (within reach of my relatively small hand), it's nearly 73%. Thus, it's more useful to keep the left hand on the keyboard. You can of course argue that one could move the right hand across, but the left
Perhaps it doesn't... (Score:2)
Re:Perhaps it doesn't... (Score:2)
Re:Perhaps it doesn't... (Score:2)
After I'm done backing up my files from my linux partition to my windwos one, linux is getting nuked, so I don't really care; I just wanted to point out that
a)maybe it doesn't run it and therefore
b)maybe it doesn't deserve to be bashed.
Re:Perhaps it doesn't... (Score:2)
Re:Perhaps it doesn't... (Score:2)
Re:Perhaps it doesn't... (Score:2)
Depends. Who's to say he didn't exicute that code in VMWare or some other protected environment? Just because somebody ran the code to see if you were telling the truth concerning whether that code actually ran, doesn't mean you should assume they were stupid and didn't run that code in some protected environment.
Same here... (Score:2)
Re:A "best-practice" in Perl is like... (Score:5, Insightful)
Re:A "best-practice" in Perl is like... (Score:4, Informative)
//
/ ^$P/ix
/^[ P.]/
/^r/
/\S/
I agree with the grandparent, I don't get how this code example means Perl is bad. You can do something similar with any language that doesn't require newlines between statements, and which allows regular expressions.
Re:A "best-practice" in Perl is like... (Score:2)
Re:A "best-practice" in Perl is like... (Score:2)
Regular expressions are a good example of something that is incredibly useful and powerful, but total gibberish to people who don't understand them. I'd hate to not have them just because some people think they're ugly.
Re:A "best-practice" in Perl is like... (Score:2)
Re:A "best-practice" in Perl is like... (Score:2)
I've seen similarly unintelligeble C, and it has the same basic problems: Bad variable names, bad whitespacing, bad blocking.
Re: (Score:2, Interesting)
Re:A "best-practice" in Perl is like... (Score:5, Funny)
000200 PROGRAM-ID. HELLOWORLD.
000300
000400*
000500 ENVIRONMENT DIVISION.
000600 CONFIGURATION SECTION.
000700 SOURCE-COMPUTER. RM-COBOL.
000800 OBJECT-COMPUTER. RM-COBOL.
000900
001000 DATA DIVISION.
001100 FILE SECTION.
001200
100000 PROCEDURE DIVISION.
100100
100200 MAIN-LOGIC SECTION.
100300 BEGIN.
100400 DISPLAY " " LINE 1 POSITION 1 ERASE EOS.
100500 DISPLAY "Hello world!" LINE 15 POSITION 10.
100600 STOP RUN.
100700 MAIN-LOGIC-EXIT.
100800 EXIT.
Re:the best practice (Score:2)
Re:the best practice (Score:2)
Re:the best practice (Score:2)
Re:Grammar Best Practices (Score:5, Informative)
Re:Perl Best Practice: Don't use it (Score:4, Insightful)
Re:What's Perl being used for today? (Score:3, Interesting)
RoR would be nice but it lacks the granularity of perl.
Re:What's Perl being used for today? (Score:2)
Re:What's Perl being used for today? (Score:2, Interesting)
Which, IMHO, is the best thing to happen to Perl. One of the main reasons why Perl got such a bad reputation is because it is very easy to pick up. The web was (and still is) littered with a huge amount of Perl snippets written by teenage script kiddies who think that Perl and CGI are synonyms (Matt's Script Archive comes to mind).
Personally, I have been using Perl professional
Re:What's Perl being used for today? (Score:2, Informative)
http://www.masonhq.com/?AmazonDotCom [masonhq.com]
(Mason, btw, is a templating system written in Perl)
Re:how about?... (Score:3, Interesting)
and Haskell is being used to _implement_ the Perl 6 compiler for the same reason Python or Ruby interpreters are writter in C. Except, of course, Haskell is a lot higher level than C and more secure, meaning the current size of the project is just short of 4K lines. and no side-effects... ^_^
Re:What's Perl being used for today? (Score:3, Informative)
CPAN? Though let me know if it's not exactly what you had in mind.
One of the reasons we're able to write quick throw-away scripts for virtually all purposes in Perl is that we have a massive Perl codebase to draw from. CPAN is often cited as one of Perl's greatest strengths, particularly against the likes of Ruby, Python, and even PHP. Not that their communities aren't moving in this direction, but the fact that each has projects whose mission statement is essentially "Be like CPAN for [insert language her
Re:What's Perl being used for today? (Score:3, Informative)
ticketmaster.com
imdb.com
slashdot.org
Just a few of the sites that run Perl...
Pugs is more of a tool to aid in development of Perl 6, it is not the official "to be released" Perl 6.
Personally I find Perl to be very useful in large scale enterprise development. You can write bad code in any language ( yes any language ), that is the fault of the programmer not the language.
It's like trying to blame a poorly constructed house on the fact your dremel tool has 9,000 options to it!
Re:What's Perl being used for today? (Score:2)
IIANM slashdot is over 6 years old and fink is at least 4.
I'm sure there are better ways to become clinically depressed than maintaining a nontrivial perl codebase, but none comes to mind atm.
Re:Nice attitude. (Score:3, Informative)
Why is this marked as offtopic?
Both comments are clearly ontopic flamebait.
For readers outside of Australia - Melbourne and Sydney have a rivalry [about.com] big enough to affected the placement of the capital (Canberra) [nationmaster.com] - it was eventually placed halfway between Sydney and Melbourne.
Even the Australian Constitution [nationmaster.com] had a clause that Canberra must be more then 100 miles
Re:Best Practice (Score:3, Insightful)
Re:Best Practice (Score:2)
Re:Best Practice (Score:3, Insightful)
Re:Best Practice (Score:2)
Re:Best Practice (Score:3, Insightful)
The problem with the program in question whe
Re:Best Practice (Score:2)
If it were all about execution speed, no one would use perl.
Re:Perl best practice number 1 (Score:3, Funny)
They have languages for that?! Oh man am I clueless.
Re:Use Python (Score:4, Insightful)
imho the power of python isnt the clear syntax, clear syntax can be written in perl too, some people are just too lazy to do it. python has really good threading and a nice oop model, perl's ithreads are still quite a mess and the variable & oop layer across it is even fuzzier and more difficult to bite through than the h4x0r'5 scripts
both languages are excellent for writing tiny helper tools for linux (tools that linux is missing a lot for dumb users), C and Java are both overkills for such simple tasks (a nice example of an overkill is a installer that is powered by a java gui, this is inhuman, uses twice the memory and need a bloating jvm to run). but without a really stable and "always being there" gui package these tools break a lot
i believe that perl is good in it's own key places, mostly being compact and very portable. in large and multithreaded applications ofcourse python rolls the house in the scripting world.
and for ruby fans, lets wait until the next version rolls out, then we may have a really good spot for that one too
use the right tool for the job and for the best practices use strict and warnings in perl, indent your code and avoid regexp hacks where you dont need them.