Array in a hash question?

[Jamie Smyth]

I have a hash defined as,

my %data = (
'wn_l' => $wn_l, 'wn_u' => $wn_u, 'wn_d' => $wn_d,
'npts' => $#spc+1, 'spc' => [@spc], 'label' => $label,
);

and I would like to extract the data in the @spc array. I tried,

my @spc = %data{'spc'};

and

my $spc = %data{'spc'};

but this results in the array being created directly in @spc[0]. I
ended up using:

my $d = $data{'spc'};
my @data = ();
push @data, @$d;

which gives me a 1dimensional array @data that I can use... the
problem is that I don't really know why this works and it looks a
little weird. Can someone explain?

Thanks.

 

[Matt Garrish]

I have a hash defined as,

my %data = (
'wn_l' => $wn_l, 'wn_u' => $wn_u, 'wn_d' => $wn_d,
'npts' => $#spc+1, 'spc' => [@spc], 'label' => $label,
);

and I would like to extract the data in the @spc array. I tried,

my @spc = %data{'spc'};

The value for key spc is a reference to an array (hash values are always
scalars). In order to access the array, you need to dereference the
reference:

my @array = @{ $data{'spc'} };

Matt

 

[Tad McClellan]

I have a hash defined as,

my %data = (
'wn_l' => $wn_l, 'wn_u' => $wn_u, 'wn_d' => $wn_d,
'npts' => $#spc+1, 'spc' => [@spc], 'label' => $label,
);

and I would like to extract the data in the @spc array.

Apply "Use Rule 1" from:

perldoc perlreftut


1) pretend is is a plain array

my @spc = @data;

2) replace the _name_ with a block ...

my @spc = @{ };

3) ... that returns a reference to an array

my @spc = @{ $data{spc} };

 

[John W. Krahn]

I have a hash defined as,

my %data = (
'wn_l' => $wn_l, 'wn_u' => $wn_u, 'wn_d' => $wn_d,
'npts' => $#spc+1, 'spc' => [@spc], 'label' => $label,
);

and I would like to extract the data in the @spc array. I tried,

my @spc = %data{'spc'};

The value for key spc is a reference to an array (hash values are always
scalars). In order to access the array, you need to dereference the
reference:

my @array = @{ $data{'spc'} };

Also, the 'npts' entry isn't required as the array in scalar context
will return the number of elements:

my $npts = @{ $data{ spc } };


John