Question

class Tree   def initialize*d;@d,=d;end   def to_s;@l||@r?',>':@d;end   def total;(@d.is_a?(Numeric)?@d:0)+(@l?@l.total: 0)+(@r?@r.total: 0);end   def insert d     alias g instance_variable_get     p=lambda{|s,o|d.to_s.send(o,@d.to_s)&&       (g(s).nil??instance_variable_set(s,Tree.new(d)):g(s).insert(d))}     @d?p[:@l,:]:@d=d   end end 

Would anyone like to take a stab at explaining what this does? It appeared as an answer in a question I asked about code that is too clever. But it’s too clever for me to tell whether it’s simply a joke. If it’s not, I’d be interested to know how it works, should anyone care to explain.

Answer 1

EDIT: The person who posted the original obfuscated example gave the actual source code in his answer. He also posted a corrected version of the obfuscated code, because as I noted, some of it didn’t make sense even when you removed the funky syntax.

That is some nicely obfuscated code. As with most obfuscated code, it’s mostly a lot of ternary operators and a stubborn refusal to put in whitespace where a normal person would. Here is basically the same thing written more normally:

class Tree   def initialize(*d)     @d,  = d # the comma is for multiple return values,              # but since there's nothing after it,              # all but the first are discarded.   end   def to_s     @l || @r ? ',>' : @d   end   def total     total = @d.is_a?(Numeric) ? @d : 0     total += @l.total if @l     total += @r.total if @r   end   def insert(arg)     if @d       if @l         @l.insert(arg)       else         @l = Tree.new(arg)       end     else       @d = arg     end   end end 

The insert method is not syntactically valid (it’s missing a method name at one part), but that’s essentially what it does as far as I can tell. The obfuscation in that method is pretty thick:

1. Instead of just doing @l = whatever, it uses instance_variable_get() and instance_variable_set(). Even worse, it aliases instance_variable_get() to just be g().

2. It wraps most of the functionality in a lambda function, to which it passes the name of the @l. Then it calls this function with the lesser-known syntax of func[arg1, arg2], which is equivalent to func.call(arg1, arg2).