Re: Elegant way to split into sequences of identical chars?

[Roy Johnson]

I know, obfuscated != elegant. Nevertheless, I thought it was kind of neat.

my $str = 'xx556xx';
my @x = grep --$|, $str =~ m/((.)\2*)/g;
print join ',', @x;

The trick with $| is that it's a toggle, so grep throws away every other member of its input. The same thing could be done with a normal variable like so:

my $str = 'xx556xx';
my $tog = 0;
my @x = grep $tog = !$tog, $str =~ m/((.)\2*)/g;
print join ',', @x;

or using split:

my $str = 'xx556xx';
my $tog = 0;
my @x = grep $tog = !$tog, split /(?<=(.))(?!\1)/, $str;
print join ',', @x;

[bioMan]

I was fascinated by the use of the $| "output autoflush". I usually use '$| = 1;' or '++$|;' for the scripts I write on Windows. So I tried the same.

my $str = 'xx556xx';
my @x = grep --$|, $str =~ m/((.)\2*)/g;
my @y = grep ++$|, $str =~ m/((.)\2*)/g;
print join ',', @x;
print "\n";
print join ',', @y;

The output being:

xx,55,6,xx

xx,x,55,5,6,6,xx,x

I was somewhat suprised as all the documentation I've seen for '$|' says a non-zero value will force fflush after every 'write' or 'print' statement. I assumed the behavior would be the same for positive and negative values. What gives?

Mike

[QM]

I've seen for '$|' says a non-zero value will force fflush after every 'write' or 'print' statement.

For a better explanation, see the thread Perl Idioms Explained - $|++, especially where it talks about ++ and --.