Implement parse_int

2 files changed, 41 insertions, 1 deletions

diff --git a/src/gleam__stdlib.erl b/src/gleam__stdlib.erl
index 8e288c0..7ee4ba8 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]).
+         decode_tuple/1, decode_list/1, decode_field/2, parse_int/1]).
 
 expect_equal(Actual, Expected) -> ?assertEqual(Expected, Actual).
 expect_not_equal(Actual, Expected) -> ?assertNotEqual(Expected, Actual).
@@ -69,3 +69,12 @@ decode_field(Data, Key) ->
     _ ->
       decode_error_msg(io_lib:format("a map with key `~p`", [Key]), Data)
   end.
+
+parse_int(String) ->
+  case string:to_integer(binary:bin_to_list(String)) of
+    {Integer, []} ->
+      {ok, Integer};
+
+    _ ->
+      {error, parse_error}
+  end.
diff --git a/src/str.gleam b/src/str.gleam
index b09b8dc..6ee8235 100644
--- a/src/str.gleam
+++ b/src/str.gleam
@@ -7,6 +7,9 @@ import list
 
 pub external fn length(String) -> Int = "string" "length"
 
+pub enum ParseError =
+  | ParseError
+
 test length {
   length("ß↑e̊")
   |> expect:equal(_, 3)
@@ -90,6 +93,34 @@ test from_int {
   |> expect:equal(_, "123")
 }
 
+pub external fn parse_int(String) -> Result(Int, ParseError) = "gleam__stdlib" "parse_int";
+
+test parse_int {
+  "123"
+  |> parse_int
+  |> expect:equal(_, Ok(123))
+
+  "-123"
+  |> parse_int
+  |> expect:equal(_, Ok(-123))
+
+  "0123"
+  |> parse_int
+  |> expect:equal(_, Ok(123))
+
+  ""
+  |> parse_int
+  |> expect:equal(_, Error(ParseError))
+
+  "what"
+  |> parse_int
+  |> expect:equal(_, Error(ParseError))
+
+  "1.23"
+  |> parse_int
+  |> expect:equal(_, Error(ParseError))
+}
+
 pub external fn base_from_int(Int, Int) -> String = "erlang" "integer_to_binary"
 
 test base_from_int {