Number of elements in an array

[Graham]

I hope the subject isn't too misleading... I am trying to find the
number of elements of each "data" array in the following:

--
use Data::Dumper;

@data = (1.0,2.0,3.0);
@test=(
{"id"=>"aaa", "units"=>"kW/m^2/st", "data"=>[@data]},
);

@data = (2.0,4.0,6.0);
push @test, {"id"=>"bbb", "units"=>"rad", "data"=>[@data]};

print Dumper @test;
print scalar($test[0]{"data"}), "\n";
--

All I can get is an address like ARRAY(0x64a0)? Surely it cannot be
that difficult to find out that there are 3 elements in each data
array ;)

Thanks.

[Ron Reidy]

Here is my output:

DB<3> x @test
0 HASH(0x8393598)
'data' => ARRAY(0x83882f8)
0 1
1 2
2 3
'id' => 'aaa'
'units' => 'kW/m2/st'
1 HASH(0x824bef8)
'data' => ARRAY(0x82a0a60)
0 2
1 4
2 6
'id' => 'bbb'
'units' => 'rad'

As you see, data is an array ref...so you should say 'print scalar
@{$test[0]{data}' and you will see what you are hoping to.

Graham wrote:

> I hope the subject isn't too misleading... I am trying to find the
> number of elements of each "data" array in the following:
>
> --
> use Data::Dumper;
>
> @data = (1.0,2.0,3.0);
> @test=(
> {"id"=>"aaa", "units"=>"kW/m^2/st", "data"=>[@data]},
> );
>
> @data = (2.0,4.0,6.0);
> push @test, {"id"=>"bbb", "units"=>"rad", "data"=>[@data]};
>
> print Dumper @test;
> print scalar($test[0]{"data"}), "\n";
> --
>
> All I can get is an address like ARRAY(0x64a0)? Surely it cannot be
> that difficult to find out that there are 3 elements in each data
> array ;)
>
> Thanks.

--
Ron Reidy
Oracle DBA

[Chief Squawtendrawpet]

Graham wrote:

> All I can get is an address like ARRAY(0x64a0)? Surely it cannot be
> that difficult to find out that there are 3 elements in each data
> array ;)

Based on your last two posts, I think you'd save yourself some grief
by spending just a few minutes brushing up on Perl references. I'd
start with 'perlreftut'.

Chief S.

[Graham]

Ron Reidy <r_reidy@comcast.net> wrote in message news:<3F5FAC79.9040301@comcast.net>...

> Here is my output:
>
> DB<3> x @test
> 0 HASH(0x8393598)
> 'data' => ARRAY(0x83882f8)
> 0 1
> 1 2
> 2 3
> 'id' => 'aaa'
> 'units' => 'kW/m2/st'
> 1 HASH(0x824bef8)
> 'data' => ARRAY(0x82a0a60)
> 0 2
> 1 4
> 2 6
> 'id' => 'bbb'
> 'units' => 'rad'
>
> As you see, data is an array ref...so you should say 'print scalar
> @{$test[0]{data}' and you will see what you are hoping to.

Many thanks '@{$test[0]{data}}' is exactly what I needed. And people
call perl a 'read-only' language ;)

[Graham]

Chief Squawtendrawpet <cs@edu.edu> wrote in message news:<3F5FB543.DD50ABDD@edu.edu>...

> Graham wrote:

> > All I can get is an address like ARRAY(0x64a0)? Surely it cannot be
> > that difficult to find out that there are 3 elements in each data
> > array ;)

>
> Based on your last two posts, I think you'd save yourself some grief
> by spending just a few minutes brushing up on Perl references. I'd
> start with 'perlreftut'.
>
> Chief S.

Thanks Chief, that is exactly what I needed. What a bizarre language.

[Tassilo v. Parseval]

Also sprach Graham:

> Ron Reidy <r_reidy@comcast.net> wrote in message news:<3F5FAC79.9040301@comcast.net>...

>> Here is my output:
>>
>> DB<3> x @test
>> 0 HASH(0x8393598)
>> 'data' => ARRAY(0x83882f8)
>> 0 1
>> 1 2
>> 2 3
>> 'id' => 'aaa'
>> 'units' => 'kW/m2/st'
>> 1 HASH(0x824bef8)
>> 'data' => ARRAY(0x82a0a60)
>> 0 2
>> 1 4
>> 2 6
>> 'id' => 'bbb'
>> 'units' => 'rad'
>>
>> As you see, data is an array ref...so you should say 'print scalar
>> @{$test[0]{data}' and you will see what you are hoping to.

>
> Many thanks '@{$test[0]{data}}' is exactly what I needed. And people
> call perl a 'read-only' language ;)

No. This is very straight-forward actually, but you may be carried away
by all those parens a little. If you have an array-ref in $ary_ref you
do

@array = @{ $ary_ref };

to dereference it back into an array.

But you can replace $ary_ref with a much more complicated expression. In
your case, the array-ref was in $test[0]{data} (actually, in
$test[0]->{data}; but the arrow can be left out as a shortcut). So the
above becomes

@array = @{ $test[0]{data} };

It can get as fancy as you want, since what you put behind @{ } can be
arbitrarily complicated Perl-code (thousands of lines if you want)...in
the end this code just has to evaluate to an array reference. This means
the last statement in it has to be the reference. Think of it as a
'return' from a subroutine:

@array = @{ print "Hello, world\n";
$test[0]{data}; };
print "@array\n";
__END__
Hello, world
1 2 3

Tassilo
--
$_=q#",}])!JAPH!qq(tsuJ[{@"tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus}) !JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?<=sub).+q#q!'"qq.\t$&."'!#+sexisexi ixesixeseg;y~\n~~dddd;eval

[Abigail]

Graham (GrahamWilsonCA@yahoo.ca) wrote on MMMDCLXIII September MCMXCIII
in <URL:news:eda30d78.0309102247.29b143c6@posting.goo gle.com>:
`'
`' Thanks Chief, that is exactly what I needed. What a bizarre language.


Feel free to use a less bizarre language instead.



Abigail
--
my $qr = qr/^.+?(;).+?\1|;Just another Perl Hacker;|;.+$/;
$qr =~ s/$qr//g;
print $qr, "\n";