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

Hola, I am trying to map two fixed and known lenght lists into a hash, preferably without using variables.

I want to replace myfunc below with a short but legible bit of code, the last attempt below ends up using $_, @_ and %_ which is a bit mean.

Any better offers?? 

my @usual = qw ( data email stuff );   #--- fixed length

my $i = 0;
my %hash;

my @input = (
    #--- rather have no function
    { username => 'fred1', myfunc ( 12, 56, 78 ) },            
    #--- no use if have to reset $i
    { username => 'fnerk', map { $usual[ $i++ ] => $_ } (33, 44, 55) }
+,
    #--- hmm
    { username => 'aargh', map { @hash{@usual} = @$_; %hash } [ 33, 44
+, 55 ] },
    #--- longwinded
    { username => 'fnerk', map { $tmp = shift @usual; 
 push @usual,$tmp; $tmp, $_ } (33, 44, 55) },
    #--- heinous
    { username => 'aargh', map { @_{ @usual } = @$_; %_ } [ 33, 44, 55
+ ] },

);

sub myfunc {
    my %flib;
    @flib{ @usual } = @_;
    return %flib;
}

for ( @input ) {
    my %local = %$_;
    for (sort keys %local ) {
       print "key : $_ : val : $local{$_} : ";
    }
    print "\n";
}

[download]

Replies are listed 'Best First'.
Re: mapping two arrays into anon hash
by Masem (Monsignor) on Jan 08, 2002 at 17:07 UTC
    Use Hash Slices: 
    use Data::Dumper;
my @usual = qw( data email stuff );
my @values = qw( 33 44 55 );
my %hash;
@hash{ @usual } = @values;
print Dumper \%hash;

    [download]

    -----------------------------------------------------
    Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
    "I can see my house from here!"
    It's not what you know, but knowing how to find it if you don't know that's important

[reply]
[d/l]
      I know about hash slices !!, and am using one in the sub...
      I'm trying to slice anonymously without defining the hash explicitly, in order to build up a data structure with the minimum amount of effort..
      looking for { username => 'fred' , @{}{@usual} fancyslice @values };
      which led me to the @_{@ary1}; %_ monstrosity...
[reply]
        You're asking for the impossible, or if it is, it's going to be an ugly mess. Sure, it's nice to get a simple result that doesn't use extra variables, but if it becomes unreadible, then you're going to confuse others as to the meaning of your code. In this case, using a temporary hash is not going to increase your memory usage save for maybe an extra byte if you create a reference to the hash, and the code will be much easier to read.

        But here's another solution that doesn't use any extra variables beyond $_: 

        use Data::Dumper;
my @names = qw ( web email stuff );
my @values = qw( 33 44 55 );
my $ref = { map { $names[$_] => $values[$_] } (0..$#names) };
print Dumper $ref;

        [download]
        (It's still not as clean as using the hash slice, IMO, but if that's what you want...)

        -----------------------------------------------------
        Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
        "I can see my house from here!"
        It's not what you know, but knowing how to find it if you don't know that's important

[reply]
[d/l]
Re (tilly) 1: mapping two arrays into anon hash
by tilly (Archbishop) on Jan 08, 2002 at 19:24 UTC
[reply]
[d/l]
Re: mapping two arrays into anon hash
by jmcnamara (Monsignor) on Jan 08, 2002 at 17:22 UTC

    You could use an array slice:     { username => 'slice', ( @usual, 33, 44, 55 )[0, 3, 1, 4, 2, 5] },I don't know if you could classify that as legible however.

    Personally, I'd prefer the subroutine approach for maintainability.

    --
    John.

[reply]
[d/l]

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