14 lines
639 B
Elixir
14 lines
639 B
Elixir
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defmodule Triangle do
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@type kind :: :equilateral | :isosceles | :scalene
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@doc """
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Return the kind of triangle of a triangle with 'a', 'b' and 'c' as lengths.
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"""
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@spec kind(number, number, number) :: {:ok, kind} | {:error, String.t()}
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def kind(a, b, c) when a <= 0 or b <= 0 or c <= 0, do: {:error, "all side lengths must be positive"}
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def kind(a, b, c) when a + b <= c or a + c <= b or b + c <= a, do: {:error, "side lengths violate triangle inequality"}
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def kind(a, a, a), do: {:ok, :equilateral}
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def kind(a, b, c) when a == b or b == c or c == a, do: {:ok, :isosceles}
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def kind(_a, _b, _c), do: {:ok, :scalene}
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end
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