Re^5: awk like question in perl

print +(split)[1,5], $/ while <DATA>;

Could also be written like this:

while ( my $line = <DATA> ) {
    my ( $second, $sixth ) = ( split //, $line )[1,5];
    print $second, $sixth, "\n";
}
[download]

The unary + sign is used to signal to Perl that you mean print( (split)[1,5], "\n" ); and not print(split[1,5]),"\n"; (which doesn't make sense, but is confusing to Perl nevertheless.

For a description of split, see split. For a description of using slices, see perldata. For a description of what $/ is, see perlvar. And for an explanation of the "do something while condition" syntax, see perlsyn.

Dave

Comment on Re^5: awk like question in perl Select or Download Code

Replies are listed 'Best First'.
Re^6: awk like question in perl by drock (Beadle) on Aug 12, 2004 at 21:12 UTC
ok so is the +(split)1,5 referencing the regexp meaning match 1 or more times? or meaning "open for reading and writing?" I a still not understanding what +(split) really means.	[reply]
Re^7: awk like question in perl by davido (Cardinal) on Aug 12, 2004 at 21:31 UTC
The snippet I provided has nothing to do with opening files. If you read the documentation for split in the links I provided, you'll see that split can take on several args or none: `split /regexp/, $splitstring, $quantity; split /regexp/, $splitstring; # quantity is assumed to be as many # as possible. split /regexp/; # $_ will be split up. split; # $_ will be split up as if the regex # looked like //.` [download] print is a function, and thus, kinda likes to be called like this: `print( "stuff" );`. You can also call it like `print "stuff";`, but if the first thing to come after `print` is an opening parenthesis, print assumes that what follows is the args to the print function. However, when you say `(split)`, you're using the parens as a list constructor, to provide list context to split, not as a parameter set for print. So how do you specify to print that you want to treat the () as a list constructor or as grouping parens instead of as function parameter parens? You treat the parens as though they're part of an expression, by prepending the unary + sign. Next, the `[1,5]` takes a slice of the list created by (split), returning only the 2nd and 6th elements. This is all kind of idiomatic, which is why I recommend backing up a step and reading the docs. Once you've done that, you should have that lightbulb flick on and you'll catch on to what's going on. Dave	[reply] [d/l] [select]