From 5ad9c72b7fb720492e1e0311f6a5147311aab97c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gabriel=20V=C3=A9rit=C3=A9?= <gabriel.lara.verite@gmail.com>
Date: Wed, 7 Aug 2024 16:43:59 +0200
Subject: [PATCH 1/2] Adds builtin functions Tree/reverse and Tree/to_list

---
 src/fun/builtins.bend                         | 33 ++++++++++++++++---
 tests/golden_tests/run_file/tree_to_list.bend |  4 +++
 .../run_file__tree_to_list.bend.snap          |  9 +++++
 3 files changed, 42 insertions(+), 4 deletions(-)
 create mode 100644 tests/golden_tests/run_file/tree_to_list.bend
 create mode 100644 tests/snapshots/run_file__tree_to_list.bend.snap

diff --git a/src/fun/builtins.bend b/src/fun/builtins.bend
index 89c04fd15..d426b5774 100644
--- a/src/fun/builtins.bend
+++ b/src/fun/builtins.bend
@@ -76,10 +76,20 @@ String/split s delim = (String/split.go s delim (List/Cons String/Nil List/Nil))
 # Create a new difference list
 DiffList/new = λx x
 
+# DiffList/wrap(head: T) -> (List(T) -> List(T)
+# Creates a new difference list with just the given value.
+def DiffList/wrap(head):
+  return lambda tail: List/Cons(head, tail)
+
 # DiffList/append(diff: List(T) -> List(T), val: T) -> (List(T) -> List(T))
 # Append a value to the end of the difference list
 DiffList/append diff val = λx (diff (List/Cons val x))
 
+# DiffList/append(left: List(T) -> List(T), right: List(T) -> List(T)) -> (List(T) -> List(T))
+# Concatenates two difference lists.
+def DiffList/concat(left, right):
+  return lambda x: left(right(x))
+
 # DiffList/cons(diff: List(T) -> List(T), val: T) -> (List(T) -> List(T))
 # Append a value to the beginning of the difference list
 DiffList/cons diff val = λx (List/Cons val (diff x))
@@ -96,7 +106,22 @@ type Tree:
   Node { ~left, ~right }
   Leaf { value }
 
-
+# Returns a List converted from a Tree.
+def Tree/to_list(tree):
+  fold tree:
+    case Tree/Leaf:
+      list = DiffList/wrap(tree.value)
+    case Tree/Node:
+      list = DiffList/concat(tree.left, tree.right)
+  return DiffList/to_list(list)
+
+# Reverses a tree swapping right and left leaves.
+def Tree/reverse(tree):
+  fold tree:
+    case Tree/Leaf:
+      return !tree.value
+    case Tree/Node:
+      return ![tree.right, tree.left]
 # MAP Impl
 
 type Map = (Node value ~left ~right) | (Leaf)
@@ -217,11 +242,11 @@ IO/FS/STDOUT = 1
 IO/FS/STDERR = 2
 
 ### Seek modes
-# Seek from start of file
+# Seek from start of file.
 IO/FS/SEEK_SET = +0
-# Seek from current position
+# Seek from current position.
 IO/FS/SEEK_CUR = +1
-# Seek from end of file
+# Seek from end of file.
 IO/FS/SEEK_END = +2
 
 ### File utilities
diff --git a/tests/golden_tests/run_file/tree_to_list.bend b/tests/golden_tests/run_file/tree_to_list.bend
new file mode 100644
index 000000000..afcd27eec
--- /dev/null
+++ b/tests/golden_tests/run_file/tree_to_list.bend
@@ -0,0 +1,4 @@
+def main:
+  var = Tree/reverse(![![!1, !2],![!3, !4]])
+  return Tree/to_list(var)
+ 
\ No newline at end of file
diff --git a/tests/snapshots/run_file__tree_to_list.bend.snap b/tests/snapshots/run_file__tree_to_list.bend.snap
new file mode 100644
index 000000000..9da109da0
--- /dev/null
+++ b/tests/snapshots/run_file__tree_to_list.bend.snap
@@ -0,0 +1,9 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/run_file/tree_to_list.bend
+---
+NumScott:
+[4, 3, 2, 1]
+
+Scott:
+[4, 3, 2, 1]

From 63ba5d22755e85f715651be18d2a8fd0f66035e2 Mon Sep 17 00:00:00 2001
From: Nicolas Abril <y906846m@anonaddy.me>
Date: Wed, 7 Aug 2024 17:24:30 +0200
Subject: [PATCH 2/2] Fix spacing in builtins file

---
 src/fun/builtins.bend | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/fun/builtins.bend b/src/fun/builtins.bend
index d426b5774..2a5f90cc1 100644
--- a/src/fun/builtins.bend
+++ b/src/fun/builtins.bend
@@ -122,6 +122,7 @@ def Tree/reverse(tree):
       return !tree.value
     case Tree/Node:
       return ![tree.right, tree.left]
+
 # MAP Impl
 
 type Map = (Node value ~left ~right) | (Leaf)