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Merged
merged 2 commits into from
Jan 9, 2025
Merged

Optimize Float.parse/1 #14159

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d3ef0bb
dk_optimize_float_parsing
dkuku Jan 8, 2025
587625e
typo
dkuku Jan 8, 2025
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28 changes: 19 additions & 9 deletions lib/elixir/lib/float.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -164,40 +164,50 @@ defmodule Float do
end

defp parse_unsigned(<<digit, rest::binary>>) when digit in ?0..?9,
do: parse_unsigned(rest, false, false, <<digit>>)
do: parse_unsigned(rest, false, false, [digit])

defp parse_unsigned(binary) when is_binary(binary), do: :error

defp parse_unsigned(<<digit, rest::binary>>, dot?, e?, acc) when digit in ?0..?9,
do: parse_unsigned(rest, dot?, e?, <<acc::binary, digit>>)
do: parse_unsigned(rest, dot?, e?, [digit | acc])

defp parse_unsigned(<<?., digit, rest::binary>>, false, false, acc) when digit in ?0..?9,
do: parse_unsigned(rest, true, false, <<acc::binary, ?., digit>>)
do: parse_unsigned(rest, true, false, [digit, ?. | acc])

defp parse_unsigned(<<exp_marker, digit, rest::binary>>, dot?, false, acc)
when exp_marker in ~c"eE" and digit in ?0..?9,
do: parse_unsigned(rest, true, true, <<add_dot(acc, dot?)::binary, ?e, digit>>)
do: parse_unsigned(rest, true, true, [digit, ?e | add_dot(acc, dot?)])

defp parse_unsigned(<<exp_marker, sign, digit, rest::binary>>, dot?, false, acc)
when exp_marker in ~c"eE" and sign in ~c"-+" and digit in ?0..?9,
do: parse_unsigned(rest, true, true, <<add_dot(acc, dot?)::binary, ?e, sign, digit>>)
do: parse_unsigned(rest, true, true, [digit, sign, ?e | add_dot(acc, dot?)])

# When floats are expressed in scientific notation, :erlang.binary_to_float/1 can raise an
# ArgumentError if the e exponent is too big. For example, "1.0e400". Because of this, we
# rescue the ArgumentError here and return an error.
defp parse_unsigned(rest, dot?, true = _e?, acc) do
:erlang.binary_to_float(add_dot(acc, dot?))
acc
|> add_dot(dot?)
|> :lists.reverse()
|> :erlang.list_to_float()
rescue
ArgumentError -> :error
else
float -> {float, rest}
end

defp parse_unsigned(rest, dot?, false = _e?, acc),
do: {:erlang.binary_to_float(add_dot(acc, dot?)), rest}
defp parse_unsigned(rest, dot?, false = _e?, acc) do
float =
acc
|> add_dot(dot?)
|> :lists.reverse()
|> :erlang.list_to_float()

{float, rest}
end

defp add_dot(acc, true), do: acc
defp add_dot(acc, false), do: acc <> ".0"
defp add_dot(acc, false), do: [?0, ?. | acc]

@doc """
Rounds a float to the largest float less than or equal to `number`.
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