Re^2: Transferring local hashes to module subroutines

Thanks for the great replies. It's working well now. Is it possible though to send an extra scalar as parameter to the subroutine? I have not been able to get this working.

sub module_subroutine {
my (%hash,$scalar) = @_;
   return "The color of the ".$scalar." is ".$hash{color};
}
my %hash_to_send;
my $scalar = "water";
$hash_to_send{color} = "red";
print module_subroutine(%hash_to_send,$scalar);
[download]

I am using strict now as suggested and it tells me there is an odd number of elements in the hash assignment at my (%hash,$scalar) = @_;. What is going on here?

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Re^3: Transferring local hashes to module subroutines by EvanK (Chaplain) on Aug 06, 2008 at 14:45 UTC
Understand that, as far as perl is concerned, passing an array or a hash is the same as passing a list of values. This is known as list context. `# functionally speaking, this.... %hash = ('a' => 1, 'b' => 2, 'c' => 3); myfunc(%hash); # is the same as this... myfunc('a', 1, 'b', 2, 'c', 3);` [download] So you'll either want to put the scalar value first and `shift` it off: `$scalar = 'blue'; %hash = ('a' => 1, 'b' => 2); myfunc($scalar, %hash); sub myfunc { my $scalar = shift; my %hash = @_; print $hash{'a'}; }` [download] Or pass arrays and hashes by reference, because when you pass a reference to an array or hash, the reference is a scalar context. `%hash = ('a' => 1, 'b' => 2); $scalar = 'blue'; myfunc(\%hash, $scalar); sub myfunc { my($hashref,$scalar) = @_; print $hashref->{'a'}; }` [download] __________ Systems development is like banging your head against a wall... It's usually very painful, but if you're persistent, you'll get through it.	[reply] [d/l] [select]
Re^3: Transferring local hashes to module subroutines by ikegami (Patriarch) on Aug 06, 2008 at 19:11 UTC
All functions accept only one thing as arguments: a list of scalar. When you do `func(%hash)`, the hash gets flatten into a list. For example `sub show_args { print(join(', ', @_), "\n"); } my %hash = ( a=>1, b=>2, c=>3 ); show_args(%hash); # c, 3, a, 1, b, 2` [download] Same goes if you also pass some scalars. `my %hash = ( a=>1, b=>2, c=>3 ); show_args(%hash, "d", 4); # c, 3, a, 1, b, 2, d, 4` [download] So when you assign @_ to a hash (or an array), the hash absorbs the entire list. Perl has no way to know that only part of the assigned list should end up in the hash unless you tell it to. Passing a reference to the hash avoids this issue too.	[reply] [d/l] [select]
Re^3: Transferring local hashes to module subroutines by dHarry (Abbot) on Aug 06, 2008 at 14:38 UTC
The problem is in the line `my (%hash,$scalar) = @_` This is not going to work ("passing both in one go"). See Passing hash and hashref to sub for a recent discussion on the topic. As usual there are more solutions to the problem. I would advice to use a hashref.	[reply] [d/l]