Pascal's triangle

# title: Pascal's triangle
# source: https://rosettacode.org/wiki/Pascal%27s_triangle
# category: Rosetta Code
# difficulty: Intro
# summary: Generate the opening rows of Pascal's triangle iteratively.
# tags: popular, math, arrays, iteration
# vibe: 0.2

def next_row(previous)
  if previous.empty?
    return [1]
  end

  row = [1]
  index = 1
  while index < previous.size
    row = row.push(previous[index - 1] + previous[index])
    index = index + 1
  end
  row = row.push(1)
  row
end

def build_triangle(rows_count)
  rows = []
  current = []
  produced = 0

  while produced < rows_count
    current = next_row(current)
    rows = rows.push(current)
    produced = produced + 1
  end

  rows
end

def run
  build_triangle(7)
end