XML::Simple for Perl Developers

An anonymous reader writes "XML has become pervasive in the computing world and is buried more and more deeply into modern applications and operating systems. It's imperative for the Perl programmer to develop a good understanding of how to use it. In a surprisingly large number of cases, you only need one tool to integrate XML into a Perl application, XML::Simple. This article tells you where to get it, how to use it, and where to go next."

Comments

Re:Who The Hell Still Uses Perl?

[Lars512]

The answer is hundreds of thousands of people around the world who use the correct tool for a given job, rather then trying to hammer in screws with the "latest and greatest".

I tend to use Python for most things, and consider it a general purpose language, suitable for all but performance critical tasks. I'd put Perl and Ruby in the same basket, as general languages with many libraries which just help you get things done. To me, these languages seem pretty interchangeable in this respect. In that case, the choice of which to use comes down to personal experience alone.

I'm curious as to whether you have a different opinion. Lets leave aside issues of syntax. What libraries or other features would you consider makes Perl the correct tool for a particular task? Are there particular tasks for which you use other scripting languages, in particular Python or Ruby?

A good tool for small tasks, but...

[Scareduck]

... utterly useless for anything of real size. XML::Simple is a huge memory sink, because, as mentioned elsewhere, it insists on generating full hash and array representations of the source XML text. This seems to be the side effect of taking too seriously a lot of Perl advice enthusiastically handed out in the older documentation. (Put file text into a huge array! Don't close your file descriptors!) The rest of us know better.

Re:Who The Hell Still Uses Perl?

[fyngyrz]

Shitty... as opposed to what, PHP?

Well, certainly as opposed to Python, anyway. I went from perl to Python with a huge sigh of relief. I try to move a still-used perl script from perl to python once a week. Eventually I'll get them all, and I can leave the language behind. But I wrote tons of perl before I discovered Python and it is a long, long road to upgrade all that stuff. But every time I do one, I get a more maintainable, more english-like tool. Sometimes it takes me several minutes to even understand what the heck a perl script (even one of mine) is trying to do. Perl just... doesn't lead you to the most readable solutions. In fact, the better at it you get, the more obscure looking your programs get, it seems to me. That's an IMHO. :)

Anyway, if someone is looking for a scripting language today, Python is the cat's meow. Readable, sensible, extensible, flexible, well supplied with great libraries of functionality, powerful as hell, very easy to debug, not unreasonable in speed.

I came in here to say this

[Wee]

Was exactly what I was going to say. I've used XML::Simple a lot, but only for reading in small documents, like config files. It works well for that. But I'd never use it on something that was bigger than, say, 100K. It's too slow and resource intensive. It does, however live up to its name. It's a very simple interface to an XML doc.

One thing I user it for was representing a database in XML. Once I had the DB layout in a datastructure, it was one line to print it out. Of course, this was before I knew about DBIx::XML_RDB...

-B

Re:Who The Hell Still Uses Perl?

[texwtf]

The fact that whitespace is dogmatized by the pyhon community makes the community
itself less attractive, and the language because of it. It sends the message that
it doesn't really matter what you want, the language is perfect and your code
is crap because you are too stupid to agree with how right the community is.

Guido could _easily_ put in some sort of pragma to allow other types of blocks, it's
only a matter of arrogance that stops him- coding with whitespace is the "right" way to do it.

There's also the matter of the parser. The last time I used Python everything was a syntax error, which gave little indication what was actually wrong with a piece of
code.

Underestimating Java

[GunFodder]

Perl is a good development language. I especially appreciate the transparency of scripting languages - if something goes wrong I can examine the source immediately. But I think you underestimate the power of Java. CPAN is good, but the resources available to a Java developer are even more extensive, thanks to the combined efforts of the major software players and the open source community. Java-specific development tools are leaps ahead of most other languages. When a serious amount of effort is required to solve an problem then it makes sense to invest time in a tool that make complex systems easier to develop and troubleshoot.

Re:Who The Hell Still Uses Perl?

[fatphil]

I recommend you start a yahoogroup for the discussion of Python. The same applies to YAML advocates too, of course. Exchange a few snippets of code/data.

Hopefully you'll then realise how non-portable a white-space-based convention is.

Perl supports comments...

[patio11]

... as one of more than one ways to do things. Unfortunately, every Perl program I have seen (with the merciful exception of POPFile) picks one of the other ways. TMTOWTDI, don't you know.

The problem with Perl isn't the language. OK, let me amend that: s/ (t)/just $1/. Its that the culture which surrounds the language encourages practices which are at odds with maintainability. You can't seperate Perl code from Perl coders, and Perl coders are, to a disturbing degree, prone to creating unmaintainable cruft with copious use of syntatic sugar which is actually disguised cyanide. Perl would be better off if some things which are syntactically allowable were banned forever. Here's a couple:

* copious use of default parameters (a wonderful way to introduce bugs into the program by accidentally overwriting one when inserting a new line of code between two sections of code which do not look obviously related)

* $_.=$& Code this obtuse needs to be discouraged, not encouraged. Its powerful, but totally obtuse, and programmer brain time is more important than finger time, which unfortunately Perl has decided to optimize for. (Incidentally: it appends the last regular expression match to whatever string you were operating on. I think.)

* Multiple methods of passing arguments to functions. (I have come across code which uses more than three in a single source file.) Function prototypes are like seatbelts. I know you think you're smart enough to not cause an accident. Statistically speaking, you're not. Buckle the heck up.

Re:Python: syntactiacally significant whitespace..

[DrVomact]

Not to mention you'd probably indent the code in any other language, python just gets rid of the extra braces.

Yeah, but once you screw up the indents in a whole file of Python source, you're not going to think that this is such a great thing. See, if you accidentally flatten out the indents of Python code, you have no clue where blocks used to begin and end. If the same thing happened in Perl, you could easily straighten things out by using the curlies as cues. (Heck, my editor will fix indents automatically for Perl.) This actually happened to me once--I accidentally sucked out all the leading spaces of every line of a Python program. The resulting mess made me re-think my infatuation with the language.

Having tried Python and having used Perl for years, I can't think of any reason why we need Python. Seems to me that anything you can do in Python you can also do in Perl. The reverse may be true, but ask yourself...does the world really need another programming language? I'm not going to be fanatic about it...use anything you think will do the job. But I'm not going to be using a language that gets upset if my indents are a off by a space, and that runs counter to my intuitive perception that white space is syntactically meaningless.