71 lines
1.5 KiB
Elixir
71 lines
1.5 KiB
Elixir
defmodule Integer do
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@moduledoc """
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Functions for working with integers.
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"""
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import Bitwise
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@doc """
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Determines if an integer is odd.
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Returns `true` if `n` is an odd number, otherwise `false`.
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Implemented as a macro so it is allowed in guard clauses.
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"""
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defmacro odd?(n) do
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quote do: (unquote(n) &&& 1) == 1
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end
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@doc """
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Determines if an integer is even.
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Returns `true` if `n` is an even number, otherwise `false`.
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Implemented as a macro so it is allowed in guard clauses.
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"""
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defmacro even?(n) do
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quote do: (unquote(n) &&& 1) == 0
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end
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@doc """
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Converts a binary to an integer.
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If successful, returns a tuple of the form `{ integer, remainder_of_binary }`.
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Otherwise `:error`.
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## Examples
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iex> Integer.parse("34")
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{34,""}
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iex> Integer.parse("34.5")
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{34,".5"}
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iex> Integer.parse("three")
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:error
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"""
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@spec parse(binary) :: { integer, binary } | :error
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def parse(<< ?-, bin :: binary >>) do
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case do_parse(bin) do
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:error -> :error
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{ number, remainder } -> { -number, remainder }
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end
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end
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def parse(<< ?+, bin :: binary >>) do
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do_parse(bin)
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end
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def parse(bin) when is_binary(bin) do
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do_parse(bin)
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end
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defp do_parse(<< char, bin :: binary >>) when char in ?0..?9, do: do_parse(bin, char - ?0)
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defp do_parse(_), do: :error
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defp do_parse(<< char, rest :: binary >>, acc) when char in ?0..?9 do
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do_parse rest, 10 * acc + (char - ?0)
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end
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defp do_parse(bitstring, acc) do
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{ acc, bitstring }
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end
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end
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