43 lines
1.4 KiB
Elixir
43 lines
1.4 KiB
Elixir
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defmodule TakeANumberDeluxe.Queue do
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# You don't need to read this module to solve this exercise.
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# We would have used Erlang's queue module instead
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# (https://www.erlang.org/doc/man/queue.html),
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# but it lacks a `delete` function before OTP 24,
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# and we want this exercise to work on older versions too.
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defstruct in: [], out: []
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@type t :: %__MODULE__{}
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@spec new() :: t()
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def new(), do: %__MODULE__{}
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@spec push(t(), any()) :: t()
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def push(%__MODULE__{in: in_q} = q, a), do: %__MODULE__{q | in: [a | in_q]}
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@spec out(t()) :: {{:value, any()}, t()} | {:empty, t()}
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def out(%__MODULE__{in: [], out: []} = q), do: {:empty, q}
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def out(%__MODULE__{out: [head | tail]} = q), do: {{:value, head}, %__MODULE__{q | out: tail}}
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def out(%__MODULE__{in: in_q}), do: out(%__MODULE__{out: Enum.reverse(in_q)})
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@spec empty?(t()) :: boolean()
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def empty?(%__MODULE__{in: [], out: []}), do: true
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def empty?(%__MODULE__{}), do: false
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@spec member?(t(), any()) :: boolean()
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def member?(%__MODULE__{in: in_q, out: out}, a), do: a in in_q or a in out
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@spec delete(t(), any()) :: t()
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def delete(%__MODULE__{in: in_q, out: out}, a) do
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out = out ++ Enum.reverse(in_q)
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out = List.delete(out, a)
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%__MODULE__{out: out}
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end
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@spec from_list([any()]) :: t()
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def from_list(list), do: %__MODULE__{out: list}
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@spec to_list(t()) :: [any()]
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def to_list(%__MODULE__{in: in_q, out: out}), do: out ++ Enum.reverse(in_q)
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end
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