From 8df0cc41c95e6c01d9c4c0fd1f57fbe96f40bbe7 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Tue, 31 Dec 2024 15:57:13 -0500
Subject: [PATCH] Array:heap_pop() now returns an optional value

---
 compile.c       |  3 ++-
 docs/arrays.md  |  8 ++++----
 stdlib/arrays.h | 10 +++++++---
 typecheck.c     |  2 +-
 4 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/compile.c b/compile.c
index 2cc3284..373762c 100644
--- a/compile.c
+++ b/compile.c
@@ -2963,7 +2963,8 @@ CORD compile(env_t *env, ast_t *ast)
                                              .type=Type(ClosureType, .fn=fn_t));
                 arg_t *arg_spec = new(arg_t, .name="by", .type=Type(ClosureType, .fn=fn_t), .default_val=default_cmp);
                 CORD arg_code = compile_arguments(env, ast, arg_spec, call->args);
-                return CORD_all("Array$heap_pop_value(", self, ", ", arg_code, ", ", padded_item_size, ", ", compile_type(item_t), ")");
+                return CORD_all("Array$heap_pop_value(", self, ", ", arg_code, ", ", compile_type(item_t), ", _, ",
+                                promote_to_optional(item_t, "_"), ", ", compile_none(item_t), ", ", padded_item_size, ")");
             } else if (streq(call->name, "binary_search")) {
                 self = compile_to_pointer_depth(env, call->self, 0, call->args != NULL);
                 type_t *item_ptr = Type(PointerType, .pointed=item_t, .is_stack=true);
diff --git a/docs/arrays.md b/docs/arrays.md
index 3bb15bd..7cae399 100644
--- a/docs/arrays.md
+++ b/docs/arrays.md
@@ -456,12 +456,12 @@ func has(arr: [T] -> Bool)
 ### `heap_pop`
 
 **Description:**  
-Removes and returns the top element of a heap. By default, this is the
-*minimum* value in the heap.
+Removes and returns the top element of a heap or `none` if the array is empty.
+By default, this is the *minimum* value in the heap.
 
 **Signature:**  
 ```tomo
-func heap_pop(arr: @[T], by: func(x,y:&T->Int32) = T.compare -> T)
+func heap_pop(arr: @[T], by: func(x,y:&T->Int32) = T.compare -> T?)
 ```
 
 **Parameters:**
@@ -471,7 +471,7 @@ func heap_pop(arr: @[T], by: func(x,y:&T->Int32) = T.compare -> T)
   default comparison function for the item type will be used.
 
 **Returns:**  
-The removed top element of the heap.
+The removed top element of the heap or `none` if the array is empty.
 
 **Example:**  
 ```tomo
diff --git a/stdlib/arrays.h b/stdlib/arrays.h
index f8921e0..cf1f088 100644
--- a/stdlib/arrays.h
+++ b/stdlib/arrays.h
@@ -107,9 +107,13 @@ void Array$heapify(Array_t *heap, Closure_t comparison, int64_t padded_item_size
 void Array$heap_push(Array_t *heap, const void *item, Closure_t comparison, int64_t padded_item_size);
 #define Array$heap_push_value(heap, _value, comparison, padded_item_size) ({ __typeof(_value) value = _value; Array$heap_push(heap, &value, comparison, padded_item_size); })
 void Array$heap_pop(Array_t *heap, Closure_t comparison, int64_t padded_item_size);
-#define Array$heap_pop_value(heap, comparison, padded_item_size, type) \
-    ({ Array_t *_heap = heap; if (_heap->length == 0) fail("Attempt to pop from an empty array"); \
-     type value = *(type*)_heap->data; Array$heap_pop(_heap, comparison, padded_item_size); value; })
+#define Array$heap_pop_value(heap, comparison, type, nonnone_var, nonnone_expr, none_expr, padded_item_size) \
+    ({ Array_t *_heap = heap; \
+     (_heap->length > 0) ? ({ \
+         type nonnone_var = *(type*)_heap->data; \
+         Array$heap_pop(_heap, comparison, padded_item_size); \
+         nonnone_expr; \
+     }) : none_expr; })
 Int_t Array$binary_search(Array_t array, void *target, Closure_t comparison);
 #define Array$binary_search_value(array, target, comparison) \
     ({ __typeof(target) _target = target; Array$binary_search(array, &_target, comparison); })
diff --git a/typecheck.c b/typecheck.c
index afbc8df..f6a75ac 100644
--- a/typecheck.c
+++ b/typecheck.c
@@ -824,7 +824,7 @@ type_t *get_type(env_t *env, ast_t *ast)
             else if (streq(call->name, "first")) return Type(OptionalType, .type=INT_TYPE);
             else if (streq(call->name, "from")) return self_value_t;
             else if (streq(call->name, "has")) return Type(BoolType);
-            else if (streq(call->name, "heap_pop")) return item_type;
+            else if (streq(call->name, "heap_pop")) return Type(OptionalType, .type=item_type);
             else if (streq(call->name, "heap_push")) return Type(VoidType);
             else if (streq(call->name, "heapify")) return Type(VoidType);
             else if (streq(call->name, "insert")) return Type(VoidType);