Ruby and Chef Syntax - Learning Chef - page 57

The results of those expressions can also be negated using the not keyword or the bang ( ! )
operand:

! true #=> false

not not true #=> false

not not false #=> true

!! true

#=> true

not not nil #=> true

Arrays

Ruby's native array support allows you to create lists of items. Ruby's arrays use the bracket
notation as shown in the following example. Arrays are zero-indexed and the Ruby interpret-
er automatically allocates memory as new items are added; there is no need to worry about
dynamically resizing arrays:

types = [ 'crispy' , 'raw' , 'crunchy' , 'grilled' ]
types . length #=> 4
types . size #=> 4
types . push 'smoked' #=> ["crispy", "raw", "crunchy", "grilled", "smoked"]
types << 'deep fried' #=> ["crispy", "raw", "crunchy", "grilled",
"smoked" , "deep fried" ]

types [ 0 ] #=> "crispy"
types . first #=> "crispy"
types . last #=> "deep fried"
types [ 0 . . 1 ] #=> ["crispy", "raw"]

The length method tells us how many items are in the array.

Yo u'll sometimes see size used as a synonym for length ; Ruby offers the choice to use
either.

Ad d one or more items to the end of the array with push .

<< is a helpful alias for push when you want to add just one item to the end.

Ar rays are zero-indexed, so we can access the first element using 0 as the index.