references and dereferences 1

[wimvanherp]

Can anybody explain this :

my %Hash;
my @List=qq(test1 test2 test3);
$Hash{ListPtr}=\@List;
my $ptr=\@List;

my @secondlist=@$Hash{ListPtr};
foreach (@secondlist)
{ print $_;}

my @thirdlist=@$ptr;
foreach (@thirdlist)
{ print $_;}

@thirdlist has the same contents as @List but @secondlist is an empty array, what 's wrong ?

greets

Wim Vanherp

 

[MillerH]

What you want is the following

my @secondlist = @{$Hash{ListPtr}};

Your original statement was dereferencing the scalar $Hash, instead of the reference found in $Hash{ListPtr}. You must therefore use brackets to indicate exactly what you are dereferencing.

If you had included a "use strict;" statement at the beginning of your script, an error would have been thrown alerting you to the syntax problem.

 

[wimvanherp]

thanks ,

i allready tried with () brackets but that did not work.


Wim Vanherp

 

[Kirsle]

(), these aren't brackets, they're parenthesis. {} these are brackets (they're the same ones that enclose if and foreach blocks).

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[ishnid]

Not to be hugely pedantic (ok, who am I kidding ;-)), but {} are braces. The term "brackets" when used by itself usually refers to square brackets [].

 

[stevexff]

ishnid

What exactly do you mean by 'pedantic'?

Steve

[small]"Every program can be reduced by one instruction, and every program has at least one bug. Therefore, any program can be reduced to one instruction which doesn't work." (Object:erlDesignPatterns)[/small]

 

[Kirsle]

I was just going by the terminology used in my all-time favorite Perl error:

Unmatched square or curly bracket at test.pl line 30

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