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Simplify Integer.digits/2 and Integer.undigits/2 #13899

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Merged
merged 3 commits into from
Oct 13, 2024
Merged

Simplify Integer.digits/2 and Integer.undigits/2 #13899

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d6b9c49
Simplify digits
MikaelFangel Oct 13, 2024
1a97884
Simplify undigits
MikaelFangel Oct 13, 2024
b25e35b
Check for base case in digits/2 instead of digits/3
MikaelFangel Oct 13, 2024
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21 changes: 12 additions & 9 deletions lib/elixir/lib/integer.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -189,13 +189,16 @@ defmodule Integer do
@spec digits(integer, pos_integer) :: [integer, ...]
def digits(integer, base \\ 10)
when is_integer(integer) and is_integer(base) and base >= 2 do
do_digits(integer, base, [])
case integer do
0 -> [0]
_integer -> digits(integer, base, [])
end
end

defp do_digits(integer, base, acc) when abs(integer) < base, do: [integer | acc]
defp digits(0, _base, acc), do: acc

defp do_digits(integer, base, acc),
do: do_digits(div(integer, base), base, [rem(integer, base) | acc])
defp digits(integer, base, acc),
do: digits(div(integer, base), base, [rem(integer, base) | acc])

@doc """
Returns the integer represented by the ordered `digits`.
Expand All @@ -217,16 +220,16 @@ defmodule Integer do
"""
@spec undigits([integer], pos_integer) :: integer
def undigits(digits, base \\ 10) when is_list(digits) and is_integer(base) and base >= 2 do
do_undigits(digits, base, 0)
undigits(digits, base, 0)
end

defp do_undigits([], _base, acc), do: acc
defp undigits([], _base, acc), do: acc

defp do_undigits([digit | _], base, _) when is_integer(digit) and digit >= base,
defp undigits([digit | _], base, _) when is_integer(digit) and digit >= base,
do: raise(ArgumentError, "invalid digit #{digit} in base #{base}")

defp do_undigits([digit | tail], base, acc) when is_integer(digit),
do: do_undigits(tail, base, acc * base + digit)
defp undigits([digit | tail], base, acc) when is_integer(digit),
do: undigits(tail, base, acc * base + digit)

@doc """
Parses a text representation of an integer.
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