Elixir: Tail Recursive Factorial - Avoids growing stack space linearly. This is related to dynamic programming: http://stackoverflow.com/q/12649970/582917

dynamic_factorial.exs

// factorial tail recursive (Elixir style)

// 4! means 1*2*3*4, we can ignore 1, which makes it 2*3*4 = 24

def factorial(number) do
    factorial(number, 1)
end

def factorial(number, product) do
    factorial(number - 1, product * number)
end

def factorial(1, product) do
    product
end

Something may have changed in recent versions of elixir. I get warning: this clause cannot match because a previous clause at line 9 always matches on line 13 and this causes an infinite loop now.

Sounds like the pattern matching system changed?

Just change the order between the last and second definitions.