# parameter passing example in Ruby

def test1 a
  a = 10
  print "in test1 -- a = "
  print a
end

def test2 a
  a[0] = 100
  print "in test2 -- a = "
  print a
end

def test3 a
  a = [200]
  print "in test3 -- a = "
  print a
end

# try these examples

# first a simple example of passing an integer
# j = 5
# test1 j
# afterwards j is still 5

# x = [1,2,3]
# When we call test2, we pass the argument by value, but the value is 
# a reference to the array x.  test2 assigns something to the 0th element 
# of its argument, and so x is changed.
# test2 x
# x


# test3 on the other hand assigns a new array to its formal parameter, so
# is unchanged
# test3 x
# x