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  1. #!/usr/bin/perl
  2.  
  3. # Idiom #281 Use a Point as a map key
  4.  
  5. package Point {
  6.     sub new { my $class = shift; bless { @_ }, $class }    
  7.  
  8.     sub x { shift->{x} };
  9.     sub y { shift->{y} };
  10.  
  11.     use overload '""' => sub { shift->_stringify() };   
  12.  
  13.     sub _stringify {
  14.         my $self = shift;
  15.         return sprintf "(%s, %s)", $self->x, $self->y; 
  16.     }
  17. }
  18.  
  19. my %m;
  20. my @points;
  21. foreach my $x (1..3) {
  22.     foreach my $y (10..12) {
  23.         my $p = Point->new(x => $x, y => $y);               
  24.         push @points, $p;
  25.         $m{$p} = $p;
  26.     }
  27. } 
  28.  
  29. for (1..5) {
  30.     my $r = $points[ int rand @points ];
  31.     printf "picked point %s got point %s\n", $r, $m{$r};
  32. }
  33.  
  34.  
  35. # for the posted idiom
  36.  
  37. my %m;
  38. my $p = Point->new(x => 42, y => 5);
  39. $m{$p} = 'Hello';
  40.  
  41. print "$p = $m{$p}";
Success #stdin #stdout 0.01s 5532KB
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Standard input is empty
stdout
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picked point (2, 11) got point (2, 11)
picked point (1, 11) got point (1, 11)
picked point (3, 11) got point (3, 11)
picked point (3, 10) got point (3, 10)
picked point (3, 12) got point (3, 12)
(42, 5) = Hello
https://ideone.com/LVdjzz
Idiom #281 Use a Point as a map key
language:
Perl (perl 5.28.1)
created:
2 years ago
visibility:
public

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