CODEWITHSUNDEEP
perl
joe
joe

Reputation: 35107

How to find all Keys in a hash have a value in Perl

How do you determine if all hash keys have some value ?

Upvotes: 2

Views: 3071

Answers (6)

J.J.
J.J.

Reputation: 4872

Here's one more way, using each. TIMTOWDI

 while (my($key, $value) = each(%hash)) {
      say "$key has no value!" if ( not defined $value);
 }

Upvotes: 0

Brad Gilbert
Brad Gilbert

Reputation: 34130

If all you want is to know if all values are defined, or any undefined this will do that:

sub all_defined{
  my( $hash ) = @_;
  for my $value ( values %$hash ){
    return '' unless defined $value; # false but defined
  }
  return 1; #true
}

Upvotes: 0

Hynek -Pichi- Vychodil
Hynek -Pichi- Vychodil

Reputation: 26141

Your question is incomplete thus this code can be answer ;-)

my %hash = (
    a => 'any value',
    b => 'some value',
    c => 'other value',
    d => 'some value'
);
my @keys_with_some_value = grep $hash{$_} eq 'some value', keys %hash;

EDIT: I had reread question again and decided that answer can be:

sub all (&@) {
  my $pred = shift();
  $pred->() or return for @_;
  return 1;
}

my $all_keys_has_some_value = all {$_ eq 'some value'} values %hash;

Upvotes: 1

Chas. Owens
Chas. Owens

Reputation: 64939

Feed the result of keys into grep with defined 

my @keys_with_values = grep { defined $hash{$_} } keys %hash;

Rereading your question, it seems like you are trying to find out if any of the values in your hash are undefined, in which case you could say something like

my @keys_without_values = grep { not defined $hash{$_} }, keys %hash;
if (@keys_without_values) {
    print "the following keys do not have a value: ",
        join(", ", @keys_without_values), "\n";
}

Upvotes: 7

Quentin
Quentin

Reputation: 944443

If the key exists, it has a value (even if that value is undef) so:

my @keys_with_values = keys %some_hash;

Upvotes: 3

Alan Haggai Alavi
Alan Haggai Alavi

Reputation: 74272

From perldoc -f exists:

               print "Exists\n"    if exists $hash{$key};
               print "Defined\n"   if defined $hash{$key};
               print "True\n"      if $hash{$key};

               print "Exists\n"    if exists $array[$index];
               print "Defined\n"   if defined $array[$index];
               print "True\n"      if $array[$index];

A hash or array element can be true only if it's defined, and defined if it exists, but the reverse doesn't necessarily hold true.

Upvotes: 10

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