How to make sequence from specific number?

Question

How to make sequence from the beginning of square number and then adding it to the previous result?

7 => 49, 56, 63, ...

def make_sequence(number)
  lambda { number*number ??? }
end

num = make_sequence(7)
num.call #=> 49
num.call #=> 56
...

Answer 1

Following your initial idea using closures I'd write:

def make_sequence(n)
  x = n**2 - n
  lambda { x += n }
end

num = make_sequence(7)
p num.call #=> 49
p num.call #=> 56

Answer 2

use Enumerator

def make_sequence(start)
  pos = start**2
  Enumerator.new do |y|
    loop do
      y.yield(pos)
      pos += start
    end
  end
end

seq = make_sequence(7)
seq.next   #=> 49
seq.next   #=> 56

...