Ruby array example

ruby-array-example.rb

array = [ :zero, :one, :two, :three, :four ]
print array.length # 5
print :four == array[4] # true — zero-indexed, so array[4] is the 5th item.
print array[5].nil? # true
print array[6].nil? #true

print [] # nil
print array[5, 0] # nil
print [] == array[5, 0] # true b/c both are nil

print nil # nil
print array[6, 0] # nil
print bil == array[5, 0] # true b/c both are nil

Ahh - there's the curvebal.

print [] == nil # returns false.

Yep. array[6,0] does not equal array[5,0]

The only thing I can think is that there's something special about the first out-of-range element (which 5 is). Like the 0 length somehow brings it back in range, or something.

In an irb session, here's what I just got:
ruby-1.8.7-p334 :004 > print array[5, 0] => nil # the return value (left) is just empty, not nil ruby-1.8.7-p334 :005 > print array[6, 0] nil => nil #the return value IS nil, not empty.

Hmm. That's interesting. I'll look into it and let you know.

Answer: http://stackoverflow.com/questions/3219229/why-does-array-slice-behave-differently-for-length-n

Consider array = [0,1,2,3]

When you specify array[4,0], you're putting the pointer where the asterisk is here: [0,1,2,3*] and then you're counting for zero length. You're still within the array. But array[4] would be nil because that is equivalent to starting at the asterisk and then going one forward, which busts you out of the array.

Ah, that makes sense. Thanks for pointing that out! Sorry I wasn't more of a concrete answer, but I'm glad you found it!