Transforming hash keys to an array

Question

I have a hash(%hash) with the following values

test0  something1
test1  something
test2  something

I need to build an array from the keys with the following elements

@test_array = part0_0 part1_0 part2_0

Basically, I have to take testx (key) and replace it as partx_0

Of course, I can easily create the array like the following

my @test_array;

foreach my $keys (keys %hash) {
    push(@test_array,$keys);
}

and I will get

@test_array = test0 test1 test2

but what I would like is to get part0_0 instead of test0, part1_0 instead of test1 and part2_0 instead of test2

Solution 1

Looks like a good time to use the non-destructive /r option for substitutions.

my @array = map s/^test(\d+)/part${1}_0/r, keys %a;

For perl versions that do not support /r:

my @array = map { s/^test(\d+)/part${1}_0/; $_ } keys %a:

Solution 2

why not do easier

my @array = ( keys %hash )

Solution 3

my @a;
for (keys %hash) {
   push @a, 'part' . ( /^test([0-9]+)/ )[0] . '_0';
}

But that just begs for map to be used.

my @a =
   map { 'part' . ( /^test([0-9]+)/ )[0] . '_0' }
    keys %hash;

Comments

[ikegami]

Note: Only available in 5.14+

[TLP]

@ikegami Where do you look that up?

[Zaid]

@TLP : perldoc perl5140delta

[TLP]

@Zaid That's only good if you already know which version it came with, though... Like a phonebook that's sorted in numerical order. =P

[Zaid]

@TLP : I sense a question coming along ;) ... go ahead and ask it before I do :)

[TLP]

@Zaid What, you want me to ask a Question-question? Nah, you go ahead.

[Zaid]

@TLP : Looks like it been asked before: stackoverflow.com/q/2500892/133939

[TLP]

@Zaid Brian d foy and at least 5 others seem to think it's limited though.. I'm testing it now, but ppm doesn't seem to like downloading Perl::MinimumVersion.

[Jacob]

perl -MPerl::MinimumVersion -E'say Perl::MinimumVersion->new(\"s///r")->minimum_version' prints 5.004. Obviously it hasn't been updated to know about /r yet.

[Ricky Levi]

in some versions of Perl you'll receive a scalar ( saying how many keys you have )

[Chris]

is this an older or newer feature? That is, in "current" versions of Perl, which way does it work?