29 lines
698 B
Elixir
29 lines
698 B
Elixir
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
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{:error, "all side lengths must be positive"}
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end
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def kind(a, b, c) when a + b <= c or b + c <= a or c + a <= b do
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{:error, "side lengths violate triangle inequality"}
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end
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def kind(a, b, c) do
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cond do
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a == b && b == c ->
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{:ok, :equilateral}
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a == b || b == c || a == c ->
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{:ok, :isosceles}
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true ->
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{:ok, :scalene}
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end
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end
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end
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