What is recursion and how does it work?

Question

Could someone please explain what exactly recursion is (and how it works in Ruby, if that\'s not too much to ask for). I came across a lengthy code snippet relying on recurs

Answer 1

Typically recursion is about method calling themselves, but maybe what you encountered were recursive structures, i.e. objects referring to themselves. Ruby 1.9 handles these really well:

h = {foo: 42, bar: 666}
parent = {child: {foo: 42, bar: 666}}
h[:parent] = parent
h.inspect # => {:foo=>42, :bar=>666, :parent=>{:child=>{...}}}

x = []
y = [x]
x << y
x.inspect # => [[[...]]]
x == [x]  # => true

I find that last line is quite wicked; I blogged about this kind of issues with comparison of recursive structures a couple of years ago.