What does a comma followed by an equals sign mean in Ruby?

Question

Just saw something like this in some Ruby code:

def getis;gets.split.map(&:to_i);end

k,=getis # What is this line doing?
di=Array::new(k){Array::new(k)}

Answer 1

It assigns the array's first element using Ruby's multiple assignment:

a, = [1, 2, 3]
a #=> 1

Or:

a, b = [1, 2, 3]
a #=> 1
b #=> 2

You can use * to fetch the remaining elements:

a, *b = [1, 2, 3]
a #=> 1
b #=> [2, 3]

Or:

*a, b = [1, 2, 3]
a #=> [1, 2]
b #=> 3