Rosetta Example: Polymorphic copy

For details see http://rosettacode.org/wiki/Polymorphic_copy

package req nx

nx::Class create T {
  :public method name {} {return T}
}
nx::Class create S -superclass T {
  :public method name {} {return S}
}

Demonstrating the behavior in a shell:

o1 and o2 are instances of T and S. $o1 name returns the same value as its copy, same for $o2

% set o1 [T new]
% set o2 [S new]

% $o1 name
T
% $o2 name
S

% [$o1 copy] name
T
% [$o2 copy] name
S