Language: C C++ D Haskell Lua OCaml PHP Perl Plain Text Python Ruby Scheme Tcl package Set::NoReplace; sub new { bless {}, shift; } sub add { $_[0]{$_[1]} = 1 unless exists $_[0]{$_[1]}; } sub del { $_[0]{$_[1]} = 0 if exists $_[0]{$_[1]}; } use overload '""' => sub { return join ', ', sort grep { $_[0]{$_} } keys %{$_[0]}; }; my $x = Set::NoReplace->new; $x->add( 3 ); $x->add( 5 ); $x->add( 1 ); print $x, "\n"; $x->del( 3 ); print $x, "\n"; $x->add( 3 ); $x->add( 7 ); print $x, "\n"; Private [?] Run code Submit