Syntax error for the following ???

mr_p has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,

I am not able to figure out the current syntax for the following error. Please help.

my (@isec , @b ) = ();
(@b, @isec) = ArrayFunctions(\@ArrayA, \@ArrayB, \@b, \@isec);
sub ArrayFunctions
{
    my $a_ref = shift; # reference to input array A
    my @a = @$a_ref; # input array A
    my $b_ref = shift; # reference to input array B
    my @b = @$b_ref; # input array B
    my $b = shift; # input array Bonly
    my $isec = shift; # input array isec_plus_bonly

    my @Aseen{@a} = (); # lookup table
    my @Bseen{@b} = (); # lookup table
#.......... Other Code .....
}
[download]

Syntax Error:

syntax error at ./dedup1.pl line 39, near "@Aseen{" Execution of ./dedup1.pl aborted due to compilation errors.

Comment on Syntax error for the following ??? Download Code

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Re: Syntax error for the following ??? by Corion (Patriarch) on Mar 30, 2010 at 17:57 UTC
You can't do `my @Aseen{...} = ...;` [download] which is what Perl tells you. Split it up into two steps and Perl will understand you: `my %Aseen; @Aseen{ @a } = ()` [download] Also, why are you copying the values from `@$a_ref` into `@a` just to use it to assign to `%Aseen` ? Why not use them directly for assigning? `@Aseen{ @$a_ref } = ()` [download]	[reply] [d/l] [select]
Re^2: Syntax error for the following ??? by mr_p (Scribe) on Mar 30, 2010 at 18:08 UTC
Worked. Thanks. Don't know how it worked without use strict.	[reply]
Re^3: Syntax error for the following ??? by AnomalousMonk (Archbishop) on Mar 30, 2010 at 20:17 UTC
Also note that in the statement `(@b,``@isec``) = ArrayFunctions(\@ArrayA, \@ArrayB, \@b, \@isec);` the array `@b` will consume the entire list returned by the `ArrayFunctions()` invocation, leaving `@isec` eternally empty. This is due to the 'list flattening' behavior of Perl.	[reply] [d/l] [select]
Re^3: Syntax error for the following ??? by ikegami (Patriarch) on Mar 30, 2010 at 21:28 UTC
It doesn't work whether `use strict;` is used or not. `$ perl -e'my @Aseen{@a} = ();' syntax error at -e line 1, near "@Aseen{" Execution of -e aborted due to compilation errors.` [download] You probably added that `my` at the same time you added `use strict;`	[reply] [d/l] [select]
Re: Syntax error for the following ??? by GrandFather (Saint) on Mar 30, 2010 at 20:46 UTC
You don't need to set arrays to empty at declaration time - they start out that way. Rather than using shift to pull off parameters one at a time in various scattered locations through your sub, use list assignment with a declaration of a list of variables at the top of the sub. If you have a reasonable variable name adding a comment that simply reiterates the variable name in expanded form doesn't add any information. Taking all that into account your code sample becomes: `my @isec; my @b; (@b, @isec) = ArrayFunctions(\@ArrayA, \@ArrayB, \@b, \@isec); sub ArrayFunctions { my ($a_ref, $b_ref, $b, $isec) = @_; my @a = @$a_ref; my @b = @$b_ref; my %Aseen = map {$_ => undef} @a; my %Bseen = map {$_ => undef} @b; #.......... Other Code ..... }` [download] Oh, and misleading comments are worse than no comment. There was a mismatch between the names of the hashes in the sub and the comment so I removed the comment. If the comment was right and names are wrong, change the names (and still omit the comment). True laziness is hard work	[reply] [d/l]