Tweak list C API:

- Rename "size" -> "count" to be consistent with other usage.
- Remove "Slot" from the function names, since that's implicit.
- Make the getListElement() just move the element to another slot. This
  matches other APIs where we distinguish accessing a value and
  converting it to some specific type.

src/include/wren.h

@@ -359,12 +359,6 @@ double wrenGetSlotDouble(WrenVM* vm, int slot);
 // foreign class.
 void* wrenGetSlotForeign(WrenVM* vm, int slot);
 
-// Returns the size of the list stored in [slot].
-int wrenGetSlotListSize(WrenVM* vm, int slot);
-
-// Reads a value from the list in [slot].
-WrenValue* wrenGetSlotListValue(WrenVM* vm, int slot, int index);
-
 // Reads a string from [slot].
 //
 // The memory for the returned string is owned by Wren. You can inspect it
@@ -431,6 +425,13 @@ void wrenSetSlotString(WrenVM* vm, int slot, const char* text);
 // This does not release the handle for the value.
 void wrenSetSlotHandle(WrenVM* vm, int slot, WrenHandle* handle);
 
+// Returns the number of elements in the list stored in [slot].
+int wrenGetListCount(WrenVM* vm, int slot);
+
+// Reads element [index] from the list in [listSlot] and stores it in
+// [elementSlot].
+void wrenGetListElement(WrenVM* vm, int listSlot, int index, int elementSlot);
+
 // Takes the value stored at [elementSlot] and inserts it into the list stored
 // at [listSlot] at [index].
 //

src/vm/wren_vm.c

@@ -1553,26 +1553,6 @@ void* wrenGetSlotForeign(WrenVM* vm, int slot)
   return AS_FOREIGN(vm->apiStack[slot])->data;
 }
 
-int wrenGetSlotListSize(WrenVM* vm, int slot)
-{
-  validateApiSlot(vm, slot);
-  ASSERT(IS_LIST(vm->apiStack[slot]),
-         "Slot must hold a list instance.");
-
-  ValueBuffer elements = AS_LIST(vm->apiStack[slot])->elements;
-  return elements.count;
-}
-
-WrenValue* wrenGetSlotListValue(WrenVM* vm, int slot, int index)
-{
-  validateApiSlot(vm, slot);
-  ASSERT(IS_LIST(vm->apiStack[slot]),
-         "Slot must hold a list instance.");
-
-  ValueBuffer elements = AS_LIST(vm->apiStack[slot])->elements;
-  return wrenCaptureValue(vm, elements.data[index]);
-}
-
 const char* wrenGetSlotString(WrenVM* vm, int slot)
 {
   validateApiSlot(vm, slot);
@@ -1649,6 +1629,25 @@ void wrenSetSlotHandle(WrenVM* vm, int slot, WrenHandle* handle)
   setSlot(vm, slot, handle->value);
 }
 
+int wrenGetListCount(WrenVM* vm, int slot)
+{
+  validateApiSlot(vm, slot);
+  ASSERT(IS_LIST(vm->apiStack[slot]), "Slot must hold a list.");
+  
+  ValueBuffer elements = AS_LIST(vm->apiStack[slot])->elements;
+  return elements.count;
+}
+
+void wrenGetListElement(WrenVM* vm, int listSlot, int index, int elementSlot)
+{
+  validateApiSlot(vm, listSlot);
+  validateApiSlot(vm, elementSlot);
+  ASSERT(IS_LIST(vm->apiStack[listSlot]), "Slot must hold a list.");
+  
+  ValueBuffer elements = AS_LIST(vm->apiStack[listSlot])->elements;
+  vm->apiStack[elementSlot] = elements.data[index];
+}
+
 void wrenInsertInList(WrenVM* vm, int listSlot, int index, int elementSlot)
 {
   validateApiSlot(vm, listSlot);

test/api/slots.c

@@ -153,17 +153,15 @@ static void foreignClassAllocate(WrenVM* vm)
   wrenSetSlotNewForeign(vm, 0, 0, 4);
 }
 
-static void getListSize(WrenVM* vm)
+static void getListCount(WrenVM* vm)
 {
-  wrenSetSlotDouble(vm, 0, wrenGetSlotListSize(vm, 1));
+  wrenSetSlotDouble(vm, 0, wrenGetListCount(vm, 1));
 }
 
-static void getListValue(WrenVM* vm)
+static void getListElement(WrenVM* vm)
 {
   int index = (int)wrenGetSlotDouble(vm, 2);
-  WrenValue* value = wrenGetSlotListValue(vm, 1, index);
-  wrenSetSlotValue(vm, 0, value);
-  wrenReleaseValue(vm, value);
+  wrenGetListElement(vm, 1, index, 0);
 }
 
 WrenForeignMethodFn slotsBindMethod(const char* signature)
@@ -174,8 +172,8 @@ WrenForeignMethodFn slotsBindMethod(const char* signature)
   if (strcmp(signature, "static Slots.slotTypes(_,_,_,_,_,_,_)") == 0) return slotTypes;
   if (strcmp(signature, "static Slots.ensure()") == 0) return ensure;
   if (strcmp(signature, "static Slots.ensureOutsideForeign()") == 0) return ensureOutsideForeign;
-  if (strcmp(signature, "static Slots.getListSize(_)") == 0) return getListSize;
-  if (strcmp(signature, "static Slots.getListValue(_,_)") == 0) return getListValue;
+  if (strcmp(signature, "static Slots.getListCount(_)") == 0) return getListCount;
+  if (strcmp(signature, "static Slots.getListElement(_,_)") == 0) return getListElement;
 
   return NULL;
 }

test/api/slots.wren

@@ -5,8 +5,8 @@ class Slots {
   foreign static slotTypes(bool, foreignObj, list, nullObj, num, string, unknown)
   foreign static ensure()
   foreign static ensureOutsideForeign()
-  foreign static getListSize(list)
-  foreign static getListValue(list, index)
+  foreign static getListCount(list)
+  foreign static getListElement(list, index)
 }
 
 foreign class ForeignType {
@@ -34,5 +34,6 @@ System.print(Slots.ensureOutsideForeign())
 // expect: 0 -> 20 (190)
 
 var ducks = ["Huey", "Dewey", "Louie"]
-System.print(Slots.getListSize(ducks))     // expect: 3
-System.print(Slots.getListValue(ducks, 1)) // expect: Dewey
+System.print(Slots.getListCount(ducks))      // expect: 3
+System.print(Slots.getListElement(ducks, 0)) // expect: Huey
+System.print(Slots.getListElement(ducks, 1)) // expect: Dewey