Anonymous functions get called with a period, versus named functions that do not:
sum = fn (a, b) -> a + b end
iex> sum.(1, 2)if the function has no arguments, still need parens to call it:
greet = fn -> IO.puts "Hello" end
# iex> greet.()parens can be omitted in a function definition:
f1 = fn a, b -> a * b end
# iex> f1.(4, 5)
f2 = fn -> 99 end
# iex> f2.()