Integer.parse/1 followed this pattern:
defp do_parse(<<char, rest :: binary>>, ...) do
...
# instead of re-using the original binary, we do this
{..., <<char, rest :: binary>>}
end
This causes a new binary to be created instead of `rest` just being a
sub-binary.
Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
265 lines
5.5 KiB
Elixir
265 lines
5.5 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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Allowed in guard clauses.
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## Examples
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iex> Integer.is_odd(3)
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true
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iex> Integer.is_odd(4)
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false
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"""
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defmacro is_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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Allowed in guard clauses.
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## Examples
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iex> Integer.is_even(10)
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true
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iex> Integer.is_even(5)
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false
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"""
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defmacro is_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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Returns the ordered digits for the given non-negative integer.
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An optional base value may be provided representing the radix for the returned
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digits.
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## Examples
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iex> Integer.digits(101)
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[1, 0, 1]
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iex> Integer.digits(58127, 2)
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[1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1]
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"""
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@spec digits(non_neg_integer, pos_integer) :: [non_neg_integer]
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def digits(n, base \\ 10) when is_integer(n) and n >= 0
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and is_integer(base) and base >= 2 do
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do_digits(n, base, [])
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end
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defp do_digits(0, _base, []), do: [0]
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defp do_digits(0, _base, acc), do: acc
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defp do_digits(n, base, acc) do
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do_digits div(n, base), base, [rem(n, base) | acc]
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end
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@doc """
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Returns the integer represented by the ordered digits.
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An optional base value may be provided representing the radix for the digits.
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## Examples
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iex> Integer.undigits([1, 0, 1])
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101
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iex> Integer.undigits([1, 4], 16)
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20
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"""
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@spec undigits([integer], integer) :: integer
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def undigits(digits, base \\ 10) when is_integer(base) do
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do_undigits(digits, base, 0)
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end
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defp do_undigits([], _base, acc), do: acc
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defp do_undigits([digit | tail], base, acc) do
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do_undigits(tail, base, acc * base + digit)
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end
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@doc """
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Converts a binary from a text representation of an integer
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in an optional base `base` to the corresponding integer.
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If the base `base` is not given, base 10 will be used.
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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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Raises an error if `base` is less than 2 or more than 36.
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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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iex> Integer.parse("34", 10)
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{34, ""}
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iex> Integer.parse("f4", 16)
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{244, ""}
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iex> Integer.parse("Awww++", 36)
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{509216, "++"}
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iex> Integer.parse("fab", 10)
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:error
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iex> Integer.parse("a2", 38)
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** (ArgumentError) invalid base 38
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"""
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@spec parse(binary, 2..36) :: {integer, binary} | :error | no_return
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def parse(binary, base \\ 10)
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def parse(binary, base) when is_integer(base) and base in 2..36 do
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parse_in_base(binary, base)
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end
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def parse(_, base) do
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raise ArgumentError, "invalid base #{base}"
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end
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defp parse_in_base("-" <> bin, base) do
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case do_parse(bin, base) 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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defp parse_in_base("+" <> bin, base) do
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do_parse(bin, base)
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end
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defp parse_in_base(bin, base) when is_binary(bin) do
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do_parse(bin, base)
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end
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defp do_parse(<<char, rest::binary>>, base) do
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if valid_digit_in_base?(char, base) do
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do_parse(rest, base, parse_digit(char, base))
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else
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:error
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end
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end
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defp do_parse(_, _), do: :error
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defp do_parse(<<char, rest::binary>> = bin, base, acc) do
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if valid_digit_in_base?(char, base) do
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do_parse(rest, base, base * acc + parse_digit(char, base))
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else
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{acc, bin}
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end
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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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defp parse_digit(char, _) do
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cond do
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char in ?0..?9 -> char - ?0
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char in ?A..?Z -> char - ?A + 10
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true -> char - ?a + 10
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end
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end
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defp valid_digit_in_base?(char, base) do
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if base <= 10 do
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char in ?0..(?0 + base - 1)
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else
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char in ?0..?9 or char in ?A..(?A + base - 11) or char in ?a..(?a + base - 11)
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end
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end
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@doc """
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Returns a binary which corresponds to the text representation
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of `some_integer`.
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Inlined by the compiler.
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## Examples
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iex> Integer.to_string(123)
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"123"
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"""
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@spec to_string(integer) :: String.t
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def to_string(some_integer) do
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:erlang.integer_to_binary(some_integer)
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end
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@doc """
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Returns a binary which corresponds to the text representation
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of `some_integer` in base `base`.
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Inlined by the compiler.
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## Examples
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iex> Integer.to_string(100, 16)
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"64"
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"""
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@spec to_string(integer, 2..36) :: String.t
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def to_string(some_integer, base) do
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:erlang.integer_to_binary(some_integer, base)
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end
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@doc """
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Returns a char list which corresponds to the text representation of the given integer.
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Inlined by the compiler.
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## Examples
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iex> Integer.to_char_list(7)
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'7'
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"""
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@spec to_char_list(integer) :: char_list
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def to_char_list(number) do
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:erlang.integer_to_list(number)
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end
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@doc """
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Returns a char list which corresponds to the text representation of the
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given integer in the given base.
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Inlined by the compiler.
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## Examples
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iex> Integer.to_char_list(1023, 16)
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'3FF'
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"""
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@spec to_char_list(integer, 2..36) :: char_list
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def to_char_list(number, base) do
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:erlang.integer_to_list(number, base)
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end
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end
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