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Programming-Idioms

  • PHP

Idiom #313 Test for map equality

Set b to true if the maps m and n have the same key/value entries, false otherwise.

sub hcmp_numeric {
    my ($h, $g) = @_;

    my $hc = keys %$h;
    my $gc = keys %$g;

    return 0 unless $hc == $gc;
    return 0 unless $hc == grep { exists $g->{$_} } keys %$h;
    die 'non-scalar value detected' 
        if 0 < grep { ref $h->{$_} or ref $g->{$_} } keys %$h;
    return 0 unless $hc == grep { $h->{$_} == $g->{$_} } keys %$h;
    return 1;
}

Returns false if the key count differs; or if the keys don't match; or if the numeric values don't match. For string values, substitute operator eq for ==. Dies if a value is not a scalar (e.g. a hash or list).
use Data::Compare;
$b = Compare( \%hash1, \%hash2 );

Comparison of hash keys is easy. Comparison of values is not, because perl hash values can be hashes or lists and nested arbitrarily. The best solution is to use CPAN Data::Compare unless the values are only strings or numbers.
#include <map>
b = m == n;
New implementation...
< > ⌨
programming-idioms.org 
sub hcmp_numeric {
    my ($h, $g) = @_;

    my $hc = keys %$h;
    my $gc = keys %$g;

    return 0 unless $hc == $gc;
    return 0 unless $hc == grep { exists $g->{$_} } keys %$h;
    die 'non-scalar value detected' 
        if 0 < grep { ref $h->{$_} or ref $g->{$_} } keys %$h;
    return 0 unless $hc == grep { $h->{$_} == $g->{$_} } keys %$h;
    return 1;
}

$b = Compare( \%hash1, \%hash2 );
b = m == n;
b := maps.Equal(m, n)
boolean b = m.equals(n);
type
  TMap = specialize TFPGMap<TKey, TData>;

function ContentEquals(m,n : TMap): Boolean;
var
  key: TKey;
  data, data2: TData;
  idx: integer;
begin
  Result := False;
  if m.count <> n.count then
    Exit;
  for idx := 0 to m.count-1 do
  begin
    key := m.keys[idx];
    Result := n.TryGetData(key, data2);
    if Result then
    begin
      data := m.data[idx];
      Result := data2 = data;
    end;
    if not Result then
      Exit;
  end;
end;

begin  
  ...
  b := ContentEquals(m,n);
b = m == n
b = m == n