Simplifying Perl Variable Types December 25, 2009
Posted by ddouthitt in Perl.Tags: types, variables
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Perl uses punctuation such as $ and @ to specify what type the variable is – scalar, array, hash, etc. When one first learns Perl, you learn:
$a = 4; # scalar @a = ( 4, 5, 6 ); # array %a = ( a => 4, b => 6 ); # hash
But then constructs like @$a (a valid construct: a reference to an array) can become confusing. If you think of these marks as operators instead, then it becomes clearer and simpler. Then $a becomes “treat a as a scalar” and @a becomes “treat a as an array”. Thus @$a is “treat $a (a is a scalar) as an array”.
The book Effective Perl Programming by Joseph Hall et al covers this and is an excellent resource for all Perl programmers. According to the book, there is a web site at http://www.effectiveperl.com but this seems to be in Russian – though it is indeed about Perl. The author, Joseph Hall, has a blog at http://effectiveperl.blogspot.com but it hasn’t been updated since 2007. At least, there’s a second edition of the book coming out soon. This book should be on every Perl programmer’s bookshelf.
Debugging: A Perl Pet Peeve December 24, 2009
Posted by ddouthitt in Debugging, Perl, Ruby.add a comment
When Ruby hit 1.45 years ago, I tried it and fell in love with it right away. The biggest problem with Ruby is the same now as it was then: its not available on every platform; most commercial UNIXes don’t include Ruby.
Thus, I have kept up my Perl skills. However, I found that debugging is not the same – and thus a pet peeve of mine.
You can always introduce print statements – which is what one of the developers of C and UNIX maintains is the only way to go (instead of “debuggers”).
When debugging Ruby, one can do this:
p $a;
When debugging Perl, this is required instead:
use Data::Dumper; print Dumper($a);
I’m also always confusing Dump() with Dumper() as well.
Why didn’t Perl use a simple method instead of a complicated library process? Who knows?
Even so, Perl has a sophisticated built-in debugger which Ruby does not – but as mentioned before, printing variable contents can be more profitable for debugging purposes.
New Version of Haskell Released: Haskell 2010 December 6, 2009
Posted by ddouthitt in Functional, Haskell.Tags: haskell 2010, haskell prime
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On November 24, Simon Marlow announced the release of the new version of the Haskell language, Haskell 2010. There are a few new features in the language, and the features will be propagating into compilers over time.
The new specification was coordinated by the Haskell Prime committee, which will continue its work in language development.
