Perl Hash of Arrays

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A Perl Hash of Arrays is a Perl Hash Data Structure that represents a Hash of Arrays Data Structure.

Example(s):
- %HoA = (A ⇒ ["v17", "v23"], B ⇒ ["v34", "v46"] )
Counter-Example(s):
- a Perl Array of Hashes.
- a Perl Hash of Hashes.
See: Perl Coding Example.

References

2001

(Cross, 2001) ⇒ David Cross. (2001). "Data Munging with Perl." Manning Publications. ISBN:1930110006

2010

(Melli, 2010) ⇒ Gabor Melli. (2010). "Perl Hash of Arrays - Examples".
- Composition of a hash of arrays
  Quotes are customarily omitted when keys are identifiers

 %HoA = (
 flintstones ⇒ ["fred", "barney" ],
 jetsons ⇒ ["george", "jane", "elroy" ],
 simpsons ⇒ ["homer", "marge", "bart" ],
 );

Generation of a hash of arrays

Reading from file with the following format: flintstones: fred barney wilma dino

 while (<> ) {
 next unless s/^(.*?):\s*'' ;
 $HoA{1ドル} = [split ];
 }

Reading from file, with more temporary variables.

 while ($line = <> ) {
 ($who, $rest) = split /:\s*/, $line, 2;
 @fields = split ' ', $rest;
 $HoA{$who} = [@fields ];
 }

calling a function that returns an array

 for $group ("simpsons", "jetsons", "flintstones" ) {
 $HoA{$group} = [get_family($group) ];
 }

likewise, but using temporary variables

for $group ("simpsons", "jetsons", "flintstones" ) {
 @members = get_family($group);
 $HoA{$group} = [@members ];
}

append new members to an existing family

push @{ $HoA{flintstones} }, "wilma", "betty";

Access and printing of a hash of arrays

one element

$HoA{flintstones}[0] = "Fred";

another element

$HoA{simpsons}[1] =~ s/(\w)/\u1ドル/;

print the wHoAe thing

foreach $family (keys %HoA ) {
 print "$family: @{ $HoA{$family} }\n";;
}

print the wHoAe thing with indices

foreach $family (keys %HoA ) {
 print "$family: ";
 foreach $i (0 .. $#{ $HoA{$family} } ) {
 print " $i = $HoA{$family}[$i]";
 }
}
print "\n";

print the wHoAe thing sorted by number of members

foreach $family (sort { @{$HoA{$b}} <=> @{$HoA{$a}} } keys %HoA ) {
 print "$family: @{ $HoA{$family} }\n";
}

print the wHoAe thing sorted by number of members and name

foreach $family (sort { @{$HoA{$b}} <=> @{$HoA{$a}} } keys %HoA ) {
 print "$family: ", join(", ", sort @{ $HoA{$family} }), "\n";
}

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