Macro/Metaprogramming approaches are possible, though my approach usually just takes an ordered list of conversions and iterates over them.
My take inside, it might spoil you!`
defmodule Roman do
@arab_to_roman [
{1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, "C"}, {90, "XC"},
{50, "L"}, {40, "XL"}, {10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"}
]
@doc """
Convert the number to a roman number.
"""
@spec numerals(1..3999) :: String.t
def numerals(number) do
Enum.reduce(@arab_to_roman, {"", number}, fn ({ar, rm}, {acc, n}) ->
{acc <> String.duplicate(rm, div(n, ar)), rem(n, ar)}
end) |> elem(0)
end
end
PS: This was created when mix format did not yet exist.
