Fix Float.parse to handle numbers of the form "-0.x"

Since Float.parse uses Integer.parse, the -0 would be
parsed independently of what came after the decimal
point and would become 0

Author: justinj

lib/elixir/lib/float.ex

@@ -22,6 +22,15 @@ defmodule Float do
 
   """
   @spec parse(binary) :: { float, binary } | :error
+
+  # Integer.parse will parse "-0" as 0, so it needs to be handled separately
+  def parse(<< "-0.", rest :: binary >>) do
+    case parse(<< ?., rest :: binary >>, 0) do
+      :error -> :error
+      { parsed, remainder } -> { -parsed, remainder }
+    end
+  end
+
   def parse(binary) when is_binary(binary) do
     case Integer.parse binary do
       :error -> :error

lib/elixir/test/elixir/float_test.exs

@@ -6,6 +6,7 @@ defmodule FloatTest do
   test :parse do
     assert Float.parse("12") === {12.0, ""}
     assert Float.parse("-12") === {-12.0, ""}
+    assert Float.parse("-0.1") === {-0.1, ""}
     assert Float.parse("123456789") === {123456789.0, ""}
     assert Float.parse("12.5") === {12.5, ""}
     assert Float.parse("12.524235") === {12.524235, ""}