def sum(*numbers)
  puts "I'm about to sum the array #{numbers.inspect}"
  numbers.inject(0) { |sum, x| sum += x }
end
sum(1, 2, 10)              

I'm about to sum the array [1, 2, 10]

I'm about to sum the array [1, 2, 10]

sum(2, -2, 2, -2, 2, -2, 2, -2, 2)

I'm about to sum the array [2, -2, 2, -2, 2, -2, 2, -2, 2]

I'm about to sum the array [2, -2, 2, -2, 2, -2, 2, -2, 2]

sum  

I'm about to sum the array []

I'm about to sum the array []

to_sum = []
1.upto(10) { |x| to_sum << x }
sum(*to_sum)

I'm about to sum the array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

I'm about to sum the array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

sum(to_sum)

I'm about to sum the array [[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]
TypeError: Array can't be coerced into Fixnum
...

I'm about to sum the array [[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]
TypeError: Array can't be coerced into Fixnum
	from (irb):3:in `+'
	from (irb):3:in `sum'
	from (irb):11:in `inject'
	from (irb):3:in `sum'
	from (irb):11

printf('%s | %s', 'left', 'right')

left | right

left | right

inputs = ['left', 'right']
printf('%s | %s', *inputs) 

left | right

left | right

def format_list(header, footer='', *data)
  puts header
  puts (line = '-' * header.size)
  puts data.join("\n")
  puts line
  puts footer
end
cozies = 21
gaskets = 10
format_list("Yesterday's productivity numbers:", 'Congratulations!', 
            "#{cozies} slime mold cozies", "#{gaskets} Sierpinski gaskets")

Yesterday's productivity numbers:
---------------------------------
21 slime mold cozies
10 Sierpinski gaskets
---------------------------------
Congratulations!

Yesterday's productivity numbers:
---------------------------------
21 slime mold cozies
10 Sierpinski gaskets
---------------------------------
Congratulations!

ranges = [[1, 10], [1, 6, true], [25, 100, false], [6, 9]]
ranges.collect { |l| Range.new(*l) }