18 lines
686 B
Plaintext
18 lines
686 B
Plaintext
defmodule Roman_numeral do
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def encode(0), do: ''
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def encode(x) when x >= 1000, do: [?M | encode(x - 1000)]
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def encode(x) when x >= 100, do: digit(div(x,100), ?C, ?D, ?M) ++ encode(rem(x,100))
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def encode(x) when x >= 10, do: digit(div(x,10), ?X, ?L, ?C) ++ encode(rem(x,10))
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def encode(x) when x >= 1, do: digit(x, ?I, ?V, ?X)
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defp digit(1, x, _, _), do: [x]
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defp digit(2, x, _, _), do: [x, x]
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defp digit(3, x, _, _), do: [x, x, x]
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defp digit(4, x, y, _), do: [x, y]
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defp digit(5, _, y, _), do: [y]
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defp digit(6, x, y, _), do: [y, x]
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defp digit(7, x, y, _), do: [y, x, x]
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defp digit(8, x, y, _), do: [y, x, x, x]
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defp digit(9, x, _, z), do: [x, z]
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end
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