Still slice impared

John M. Dlugosz has asked for the wisdom of the Perl Monks concerning the following question:

What is the syntax to take a slice of a list reference? The following gives me Argument "" isn't numeric in array element with the warning message indicating the @left= line.

 my ($self, $n)= @_;
 my $len= scalar @$self;
 print " *** n=$n, len=$len\n";
 my @left= $self->[0..$n-1];
 my @right= $self->[$n..$len-1];
[download]

The print indicates that n=1, and len=6. $self is [1, 2, 3, 4, 5, 6] using BigInt's.

What I want to do is put n items in @left and the remaining items in @right.

—John

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Re: Still slice impared by davido (Cardinal) on Feb 24, 2004 at 06:22 UTC
If $self is an array-ref... `my @slice = @{$self}[0..$n-1];` [download] That ought to do it. The curly brackets are being used in this case for clarity. It can also be expressed like this: `my @slice = @$self[0..$n-1];` [download] ....at least in my test cases that seems to work just fine. ;) Dave	[reply] [d/l] [select]
Re: Re: Still slice impared by John M. Dlugosz (Monsignor) on Feb 24, 2004 at 15:41 UTC
Thanks. In my code, the actual results indicate that the array indexing takes the first element of the list only. But, any idea where the warning about "" not being a numeric argument could be coming from?	[reply]
Re: Re: Re: Still slice impared by ysth (Canon) on Feb 24, 2004 at 17:25 UTC
From the ".." flipflop operator in scalar context.	[reply]
Re: Still slice impared by Enlil (Parson) on Feb 24, 2004 at 06:35 UTC
davido, answered your question. but here is another way to do it (TIMTOWTDI and all that). What I want to do is put n items in @left and the remaining items in @right. `my (@right, @left); (@left[0 .. $n - 1], @right) = @$self;` [download] -enlil	[reply] [d/l]
Re: Still slice impared by revdiablo (Prior) on Feb 24, 2004 at 18:40 UTC
a slice of a list reference Hate to be nitpicky (and the question has already been answered sufficiently), but there's no such thing as a list reference. That would be an array reference. A list is not a type of variable, whereas an array is. So you can only take a reference to an array, not a list.	[reply]