result.Option type alias

8 files changed, 45 insertions, 31 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 94080c7..615aff8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,6 +17,6 @@ jobs:
           otp-version: 22.2
       - uses: gleam-lang/setup-gleam@v1.0.1
         with:
-          gleam-version: 0.6.0
+          gleam-version: 0.7.0-rc1
       - run: rebar3 install_deps
       - run: rebar3 eunit
diff --git a/gen/src/gleam@list.erl b/gen/src/gleam@list.erl
index c33dab2..3e6d01d 100644
--- a/gen/src/gleam@list.erl
+++ b/gen/src/gleam@list.erl
@@ -24,7 +24,7 @@ contains(List, Elem) ->
 head(List) ->
     case List of
         [] ->
-            {error, nil};
+            gleam@result:none();
 
         [X | _] ->
             {ok, X}
@@ -33,7 +33,7 @@ head(List) ->
 tail(List) ->
     case List of
         [] ->
-            {error, nil};
+            gleam@result:none();
 
         [_ | Xs] ->
             {ok, Xs}
@@ -172,7 +172,7 @@ fold_right(List, Initial, Fun) ->
 find(Haystack, IsDesired) ->
     case Haystack of
         [] ->
-            {error, nil};
+            gleam@result:none();
 
         [X | Rest] ->
             case IsDesired(X) of
@@ -187,7 +187,7 @@ find(Haystack, IsDesired) ->
 find_map(Haystack, Fun) ->
     case Haystack of
         [] ->
-            {error, nil};
+            gleam@result:none();
 
         [X | Rest] ->
             case Fun(X) of
@@ -258,19 +258,19 @@ intersperse(List, Elem) ->
         [X] ->
             [X];
 
-        [X | Rest] ->
-            [X, Elem | intersperse(Rest, Elem)]
+        [X1 | Rest] ->
+            [X1, Elem | intersperse(Rest, Elem)]
     end.
 
 at(List, Index) ->
     case Index < 0 of
         true ->
-            {error, nil};
+            gleam@result:none();
 
         false ->
             case List of
                 [] ->
-                    {error, nil};
+                    gleam@result:none();
 
                 [X | Rest] ->
                     case Index =:= 0 of
@@ -396,5 +396,5 @@ key_find(KeywordList, DesiredKey) ->
                     {ok, Value};
 
                 false ->
-                    {error, nil}
+                    gleam@result:none()
             end end).
diff --git a/gen/src/gleam@result.erl b/gen/src/gleam@result.erl
index 3aeae12..2484f56 100644
--- a/gen/src/gleam@result.erl
+++ b/gen/src/gleam@result.erl
@@ -1,7 +1,7 @@
 -module(gleam@result).
 -compile(no_auto_import).
 
--export([is_ok/1, is_error/1, map/2, map_error/2, flatten/1, then/2, unwrap/2]).
+-export([is_ok/1, is_error/1, map/2, map_error/2, flatten/1, then/2, unwrap/2, none/0]).
 
 is_ok(Result) ->
     case Result of
@@ -65,3 +65,6 @@ unwrap(Result, Default) ->
         {error, _} ->
             Default
     end.
+
+none() ->
+    {error, nil}.
diff --git a/src/gleam/float.gleam b/src/gleam/float.gleam
index 117467e..653a4d6 100644
--- a/src/gleam/float.gleam
+++ b/src/gleam/float.gleam
@@ -1,7 +1,8 @@
 import gleam/iodata
 import gleam/order.{Order}
+import gleam/result.{Option}
 
-pub external fn parse(String) -> Result(Float, Nil)
+pub external fn parse(String) -> Option(Float)
   = "gleam_stdlib" "parse_float";
 
 pub fn to_string(f: Float) -> String {
diff --git a/src/gleam/int.gleam b/src/gleam/int.gleam
index c152be4..7fd7fa6 100644
--- a/src/gleam/int.gleam
+++ b/src/gleam/int.gleam
@@ -1,6 +1,7 @@
 import gleam/order.{Order}
+import gleam/result.{Option}
 
-pub external fn parse(String) -> Result(Int, Nil) = "gleam_stdlib" "parse_int";
+pub external fn parse(String) -> Option(Int) = "gleam_stdlib" "parse_int";
 
 pub external fn to_string(Int) -> String = "erlang" "integer_to_binary"
 
diff --git a/src/gleam/list.gleam b/src/gleam/list.gleam
index 527c1c8..eaa0b23 100644
--- a/src/gleam/list.gleam
+++ b/src/gleam/list.gleam
@@ -1,6 +1,7 @@
 import gleam/int
-import gleam/order.{Order}
 import gleam/pair
+import gleam/order.{Order}
+import gleam/result.{Option}
 
 pub type LengthMismatch {
   LengthMismatch
@@ -25,16 +26,16 @@ pub fn contains(list: List(a), has elem: a) -> Bool {
   }
 }
 
-pub fn head(list: List(a)) -> Result(a, Nil) {
+pub fn head(list: List(a)) -> Option(a) {
   case list {
-    [] -> Error(Nil)
+    [] -> result.none()
     [x | _] -> Ok(x)
   }
 }
 
-pub fn tail(list: List(a)) -> Result(List(a), Nil) {
+pub fn tail(list: List(a)) -> Option(List(a)) {
   case list {
-    [] -> Error(Nil)
+    [] -> result.none()
     [_ | xs] -> Ok(xs)
   }
 }
@@ -83,7 +84,6 @@ pub fn index_map(list: List(a), with fun: fn(Int, a) -> b) -> List(b) {
   do_index_map(list, fun, 0, [])
 }
 
-// fn do_traverse(list: List(a), fun: fn(a) -> Result(b, e), acc: List(b)) -> Result(List(b), e) {
 fn do_traverse(
   list: List(a),
   fun: fn(a) -> Result(b, e),
@@ -171,9 +171,9 @@ pub fn fold_right(
 pub fn find(
   in haystack: List(a),
   one_that is_desired: fn(a) -> Bool,
-) -> Result(a, Nil) {
+) -> Option(a) {
   case haystack {
-    [] -> Error(Nil)
+    [] -> result.none()
     [x | rest] ->
       case is_desired(x) {
         True -> Ok(x)
@@ -184,10 +184,10 @@ pub fn find(
 
 pub fn find_map(
   in haystack: List(a),
-  with fun: fn(a) -> Result(b, Nil),
-) -> Result(b, Nil) {
+  with fun: fn(a) -> Option(b),
+) -> Option(b) {
   case haystack {
-    [] -> Error(Nil)
+    [] -> result.none()
     [x | rest] ->
       case fun(x) {
         Ok(x) -> Ok(x)
@@ -241,12 +241,12 @@ pub fn intersperse(list: List(a), with elem: a) -> List(a) {
   }
 }
 
-pub fn at(in list: List(a), get index: Int) -> Result(a, Nil) {
+pub fn at(in list: List(a), get index: Int) -> Option(a) {
   case index < 0 {
-    True -> Error(Nil)
+    True -> result.none()
     False ->
     case list {
-      [] -> Error(Nil)
+      [] -> result.none()
       [x | rest] ->
       case index == 0 {
         True -> Ok(x)
@@ -354,12 +354,12 @@ pub fn split_while(
 pub fn key_find(
   in keyword_list: List(tuple(k, v)),
   find desired_key: k,
-) -> Result(v, Nil) {
+) -> Option(v) {
   find_map(keyword_list, fn(keyword) {
     let tuple(key, value) = keyword
     case key == desired_key {
       True -> Ok(value)
-      False -> Error(Nil)
+      False -> result.none()
     }
   })
 }
diff --git a/src/gleam/map.gleam b/src/gleam/map.gleam
index a57605a..848d5a6 100644
--- a/src/gleam/map.gleam
+++ b/src/gleam/map.gleam
@@ -1,5 +1,6 @@
 import gleam/result
 import gleam/list
+import gleam/result.{Option}
 
 pub external type Map(key, value);
 
@@ -22,7 +23,7 @@ pub fn has_key(map: Map(k, v), key: k) -> Bool {
 pub external fn new() -> Map(key, value)
   = "maps" "new"
 
-pub external fn get(from: Map(key, value), get: key) -> Result(value, Nil)
+pub external fn get(from: Map(key, value), get: key) -> Option(value)
   = "gleam_stdlib" "map_get";
 
 external fn erl_insert(key, value, Map(key, value)) -> Map(key, value)
@@ -80,7 +81,7 @@ pub fn drop(from map: Map(k, v), drop disallowed_keys: List(k)) -> Map(k, v) {
 pub fn update(
   in map: Map(k, v),
   update key: k,
-  with fun: fn(Result(v, Nil)) -> v,
+  with fun: fn(Option(v)) -> v,
 ) -> Map(k, v) {
   map |> get(_, key) |> fun |> insert(map, key, _)
 }
diff --git a/src/gleam/result.gleam b/src/gleam/result.gleam
index 28b7d96..9abbaea 100644
--- a/src/gleam/result.gleam
+++ b/src/gleam/result.gleam
@@ -58,3 +58,11 @@ pub fn unwrap(result: Result(a, e), or default: a) -> a {
     Error(_) -> default
   }
 }
+
+// A value that is either there or not there
+pub type Option(value) =
+  Result(value, Nil)
+
+pub fn none() -> Option(a) {
+  Error(Nil)
+}