Self-referential hashes

Explanation

hash = {a: 1}
hash[:b] = hash

hash[:b][:b][:b][:a] # => 1

Explanation

1. Initialization: We start by creating a hash with a single key-value pair:

hash = {a: 1}

At this point, the hash looks like this:

{a: 1}

1. Self-Referencing Assignment: We then assign the :b key to point to the hash itself:

hash[:b] = hash

Now the hash references itself under the key :b, making it recursive:

{a: 1, b: {a: 1, b: {...}}}

The :b key holds a reference to the original hash, which includes itself.

1. Chained Access: Finally, we access the :b key repeatedly:

hash[:b][:b][:b][:a]

Here’s how Ruby interprets this:

• hash[:b] gives us the original hash.
• hash[:b][:b] gives us the original hash again.
• hash[:b][:b][:b] continues to return the original hash.

So, every time we access :b, we're just retrieving the original hash, which is {a: 1, b: {a: 1, b: {...}}}.

1. Final Access: After resolving all the :b keys, we access the :a key of the final hash:

hash[:b][:b][:b][:a]

Since :a was originally set to 1, this entire chain of access ultimately returns:

hash[:b][:b][:b][:a] # => 1