gistfile1.rb

params = {
  :font_size => 10
}

# 1 
defaults = {
  :font => "Times-Roman",
  :font_size => 11,
  :stroke => false
}
defaults.each do |key, value|
  if not params.include? key
    params[key] = value
  end
end

# 2 
defaults = {
  :font => "Times-Roman",
  :font_size => 11,
  :stroke => false
}
params = defaults.merge params

# 3
params = {
  :font => "Times-Roman",
  :font_size => 11,
  :stroke => false
}.merge params