Implement parse_float

2 files changed, 38 insertions, 1 deletions

diff --git a/src/gleam__stdlib.erl b/src/gleam__stdlib.erl
index 7ee4ba8..05623c6 100644
--- a/src/gleam__stdlib.erl
+++ b/src/gleam__stdlib.erl
@@ -6,7 +6,7 @@
          atom_create_from_string/1, atom_to_string/1, map_fetch/2,
          iodata_append/2, iodata_prepend/2, identity/1, decode_int/1,
          decode_string/1, decode_bool/1, decode_float/1, decode_thunk/1,
-         decode_tuple/1, decode_list/1, decode_field/2, parse_int/1]).
+         decode_tuple/1, decode_list/1, decode_field/2, parse_int/1, parse_float/1]).
 
 expect_equal(Actual, Expected) -> ?assertEqual(Expected, Actual).
 expect_not_equal(Actual, Expected) -> ?assertNotEqual(Expected, Actual).
@@ -78,3 +78,12 @@ parse_int(String) ->
     _ ->
       {error, parse_error}
   end.
+
+parse_float(String) ->
+  case string:to_float(binary:bin_to_list(String)) of
+    {Float, []} ->
+      {ok, Float};
+
+    _ ->
+      {error, parse_error}
+  end.
diff --git a/src/str.gleam b/src/str.gleam
index 6ee8235..bd027a1 100644
--- a/src/str.gleam
+++ b/src/str.gleam
@@ -121,6 +121,34 @@ test parse_int {
   |> expect:equal(_, Error(ParseError))
 }
 
+pub external fn parse_float(String) -> Result(Float, ParseError) = "gleam__stdlib" "parse_float";
+
+test parse_float {
+  "1.23"
+  |> parse_float
+  |> expect:equal(_, Ok(1.23))
+
+  "5.0"
+  |> parse_float
+  |> expect:equal(_, Ok(5.0))
+
+  "0.123456789"
+  |> parse_float
+  |> expect:equal(_, Ok(0.123456789))
+
+  ""
+  |> parse_float
+  |> expect:equal(_, Error(ParseError))
+
+  "what"
+  |> parse_float
+  |> expect:equal(_, Error(ParseError))
+
+  "1"
+  |> parse_float
+  |> expect:equal(_, Error(ParseError))
+}
+
 pub external fn base_from_int(Int, Int) -> String = "erlang" "integer_to_binary"
 
 test base_from_int {