String.to_integer and String.to_float

lib/elixir/lib/string.ex

@@ -670,4 +670,64 @@ defmodule String do
  _ -> acc
  end
  end
+
+ @doc """
+ Converts a string to an integer. If successful, returns a
+ tuple of form {integer, remainder of string}. If unsuccessful,
+ returns :error.
+
+ ## Examples
+
+ iex> String.to_integer("34")
+ {34,""}
+ iex> String.to_integer("34.5")
+ {34,".5"}
+ iex> String.to_integer("three")
+ :error
+
+ """
+ @spec to_integer(t) :: {integer, t} | :error
+
+ def to_integer(string) do
+ {result, remainder} = :string.to_integer(binary_to_list(string))
+ case result do
+ :error -> :error
+ _ -> {result, list_to_binary(remainder)}
+ end
+ end
+
+ @doc """
+ Converts a string to a float. If successful, returns a
+ tuple of form {float, remainder of string}. If unsuccessful,
+ returns :error. If given an integer value, will return
+ same as to_integer/1.
+
+ ## Examples
+
+ iex> String.to_float("34")
+ {34.0,""}
+ iex> String.to_float("34.25")
+ {34.25,""}
+ iex> String.to_float("56.5xyz")
+ {56.5,"xyz"}
+ iex> String.to_float("pi")
+ :error
+
+ """
+ @spec to_float(t) :: {integer, t} | :error
+
+ def to_float(string) do
+ charlist = binary_to_list(string)
+ {result, remainder} = :string.to_float(charlist)
+ case result do
+ :error -> 
+ {int_result, int_remainder} = :string.to_integer(charlist)
+ case int_result do
+ :error -> :error
+ _ -> {float(int_result), list_to_binary(int_remainder)}
+ end
+ _ -> {result, list_to_binary(remainder)}
+ end
+ end
+
 end

lib/elixir/test/elixir/string_test.exs

@@ -237,4 +237,30 @@ defmodule StringTest do
  refute String.valid_codepoint?("ab")
  end
 
+ test :to_integer do
+ assert String.to_integer("12") == {12,""}
+ assert String.to_integer("-12") == {-12,""}
+ assert String.to_integer("123456789") == {123456789,""}
+ assert String.to_integer("12.5") == {12,".5"}
+ assert String.to_integer("7.5e-3") == {7,".5e-3"}
+ assert String.to_integer("12x") == {12,"x"}
+ assert String.to_integer("three") == :error
+ end
+
+ test :to_float do
+ assert String.to_float("12") == {12.0,""}
+ assert String.to_float("-12") == {-12.0,""}
+ {value, _remdr} = String.to_float("12");
+ refute value === 12
+ assert String.to_float("123456789") == {123456789.0,""}
+ assert String.to_float("12.5") == {12.5,""}
+ assert String.to_float("-12.5") == {-12.5,""}
+ assert String.to_float("7.5e3") == {7.5e3,""}
+ assert String.to_float("7.5e-3") == {7.5e-3,""}
+ assert String.to_float("12x") == {12.0,"x"}
+ assert String.to_float("12.5x") == {12.5,"x"}
+ assert String.to_float("pi") == :error
+ end
+
+
 end