monotonically accumulate versions of definitions

One old drawback now has a new look. Before, we loaded definitions in
order, so global definitions had to exist before other global
definitions that used them. See window and grid in life.tlv. Now we load
definitions in reverse order, so initialization needs to change. Worse,
if we update window, we need to edit grid just to fix the order.

This implies that we can't yet optimize away bindings where there are no
new changes.

1 files changed, 137 insertions, 71 deletions

diff --git a/src/lua.c b/src/lua.c
index 1e88b8b..460436d 100644
--- a/src/lua.c
+++ b/src/lua.c
@@ -280,27 +280,64 @@ void stack_dump (lua_State *L) {
 }
 
 
+static int binding_exists (lua_State *L, const char *name) {
+  int result = 0;
+  lua_getglobal(L, name);
+  result = !lua_isnil(L, -1);
+  lua_pop(L, 1);
+  return result;
+}
+
+
+static const char *look_up_definition (lua_State *L, const char *name) {
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  /* iterate over mutations in teliva_program history in reverse order */
+  int history_array_size = luaL_getn(L, history_array);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int table = lua_gettop(L);
+    /* iterate over bindings */
+    /* really we expect only one */
+    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+      const char* key = lua_tostring(L, -2);
+      if (strcmp(key, name) == 0)
+        return lua_tostring(L, -1);
+    }
+  }
+  lua_pop(L, 1);
+  return NULL;
+}
+
+
 char *Image_name = NULL;
 static int handle_image (lua_State *L, char **argv, int n) {
   int status;
   int narg = getargs(L, argv, n);  /* collect arguments */
   lua_setglobal(L, "arg");
-  /* parse and load file contents (teliva_program table) */
+  /* parse and load file contents (teliva_program array) */
   Image_name = argv[n];
   status = luaL_loadfile(L, Image_name);
   lua_insert(L, -(narg+1));
-  if (status != 0) {
-    return status;
-  }
+  if (status != 0) return status;
   status = docall(L, narg, 0);
   lua_getglobal(L, "teliva_program");
-  int table = lua_gettop(L);
-  /* parse and load each binding in teliva_program */
-  for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
-    const char* key = lua_tostring(L, -2);
-    const char* value = lua_tostring(L, -1);
-    status = dostring(L, value, key);
-    if (status != 0) return report(L, status);
+  int history_array = lua_gettop(L);
+  /* iterate over mutations in teliva_program history in reverse order */
+  int history_array_size = luaL_getn(L, history_array);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int table = lua_gettop(L);
+    /* iterate over bindings */
+    /* really we expect only one */
+    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+      const char* key = lua_tostring(L, -2);
+      if (binding_exists(L, key))
+        continue;  // most recent binding trumps older ones
+      const char* value = lua_tostring(L, -1);
+      status = dostring(L, value, key);
+      if (status != 0) return report(L, status);
+    }
   }
   /* call main() */
   lua_getglobal(L, "main");
@@ -314,10 +351,7 @@ static int handle_image (lua_State *L, char **argv, int n) {
 char Current_definition[CURRENT_DEFINITION_LEN+1] = {0};
 void save_to_current_definition_and_editor_buffer (lua_State *L, const char *definition) {
   strncpy(Current_definition, definition, CURRENT_DEFINITION_LEN);
-  lua_getglobal(L, "teliva_program");
-  lua_getfield(L, -1, Current_definition);
-  const char *contents = lua_tostring(L, -1);
-  lua_pop(L, 1);
+  const char *contents = look_up_definition(L, Current_definition);
   FILE *out = fopen("teliva_editbuffer", "w");
   if (contents != NULL)
     fprintf(out, "%s", contents);
@@ -333,27 +367,42 @@ static void read_editor_buffer (char *out) {
 }
 
 
-/* table to update is at top of stack */
-static void update_definition (lua_State *L, const char *name, char *out) {
+static void update_definition (lua_State *L, const char *name, char *new_contents) {
+  assert(lua_gettop(L) == 0);
   lua_getglobal(L, "teliva_program");
-  lua_pushstring(L, out);
+  int history_array = 1;
+  /* create a new table containing a single binding */
+  lua_createtable(L, /*number of fields per mutation*/2, 0);
+  lua_pushstring(L, new_contents);
   assert(strlen(name) > 0);
   lua_setfield(L, -2, name);
+  /* append the new table to the history of mutations */
+  int history_array_size = luaL_getn(L, history_array);
+  ++history_array_size;
+  lua_rawseti(L, history_array, history_array_size);
   lua_settop(L, 0);
 }
 
 
 static void save_image (lua_State *L) {
   lua_getglobal(L, "teliva_program");
-  int table = lua_gettop(L);
-  FILE *out = fopen(Image_name, "w");
+  int history_array = lua_gettop(L);
+  int history_array_size = luaL_getn(L, history_array);
+  FILE* out = fopen(Image_name, "w");
   fprintf(out, "teliva_program = {\n");
-  for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
-    const char *key = lua_tostring(L, -2);
-    const char *value = lua_tostring(L, -1);
-    fprintf(out, "  %s = [==[", key);
-    fprintf(out, "%s", value);
-    fprintf(out, "]==],\n");
+  for (int i = 1;  i <= history_array_size; ++i) {
+    lua_rawgeti(L, history_array, i);
+    int table = lua_gettop(L);
+    fprintf(out, "  {\n");
+    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+      const char* key = lua_tostring(L, -2);
+      const char* value = lua_tostring(L, -1);
+      fprintf(out, "    %s = [==[\n", key);
+      fprintf(out, "%s", value);
+      fprintf(out, "]==],\n");
+    }
+    fprintf(out, "  },\n");
+    lua_pop(L, 1);
   }
   fprintf(out, "}\n");
   fclose(out);
@@ -434,46 +483,55 @@ int browse_image (lua_State *L) {
   clear();
   luaL_newmetatable(L, "__teliva_call_graph_depth");
   int cgt = lua_gettop(L);
-  // special-case: we don't instrument the call to main, but it's always 1
+  // special-case: we don't instrument the call to main, but it's always at depth 1
   lua_pushinteger(L, 1);
   lua_setfield(L, cgt, "main");
   // segment definitions by depth
   lua_getglobal(L, "teliva_program");
-  int t = lua_gettop(L);
+  int history_array = lua_gettop(L);
+  int history_array_size = luaL_getn(L, history_array);
 
   int y = 2;
   mvaddstr(y, 0, "data:           ");
   // first: data (non-functions) that's not the Teliva menu or curses variables
-  for (lua_pushnil(L); lua_next(L, t) != 0;) {
-    const char *definition_name = lua_tostring(L, -2);
-    lua_getglobal(L, definition_name);
-    int is_userdata = lua_isuserdata(L, -1);
-    int is_function = lua_isfunction(L, -1);
-    lua_pop(L, 1);
-    if (strcmp(definition_name, "menu") != 0  // required by all Teliva programs
-        && !is_function  // functions are not data
-        && !is_userdata  // including curses window objects
-                         // (unlikely to have an interesting definition)
-    ) {
-      browse_definition(definition_name);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0;) {
+      const char *definition_name = lua_tostring(L, -2);
+      lua_getglobal(L, definition_name);
+      int is_userdata = lua_isuserdata(L, -1);
+      int is_function = lua_isfunction(L, -1);
+      lua_pop(L, 1);
+      if (strcmp(definition_name, "menu") != 0  // required by all Teliva programs
+          && !is_function  // functions are not data
+          && !is_userdata  // including curses window objects
+                           // (unlikely to have an interesting definition)
+      ) {
+        browse_definition(definition_name);
+      }
+      lua_pop(L, 1);  // value
+      // leave key on stack for next iteration
     }
-    lua_pop(L, 1);  // value
-    // leave key on stack for next iteration
   }
 
   // second: menu and other userdata
-  for (lua_pushnil(L); lua_next(L, t) != 0;) {
-    const char* definition_name = lua_tostring(L, -2);
-    lua_getglobal(L, definition_name);
-    int is_userdata = lua_isuserdata(L, -1);
-    lua_pop(L, 1);
-    if (strcmp(definition_name, "menu") == 0
-        || is_userdata  // including curses window objects
-    ) {
-      browse_definition(definition_name);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0;) {
+      const char* definition_name = lua_tostring(L, -2);
+      lua_getglobal(L, definition_name);
+      int is_userdata = lua_isuserdata(L, -1);
+      lua_pop(L, 1);
+      if (strcmp(definition_name, "menu") == 0
+          || is_userdata  // including curses window objects
+      ) {
+        browse_definition(definition_name);
+      }
+      lua_pop(L, 1);  // value
+      // leave key on stack for next iteration
     }
-    lua_pop(L, 1);  // value
-    // leave key on stack for next iteration
   }
 
   // functions by level
@@ -482,32 +540,40 @@ int browse_image (lua_State *L) {
   y++;
   for (int level = 1; level < 5; ++level) {
     mvaddstr(y, 0, "                ");
+    for (int i = history_array_size; i > 0; --i) {
+      lua_rawgeti(L, history_array, i);
+      int t = lua_gettop(L);
+      for (lua_pushnil(L); lua_next(L, t) != 0;) {
+        const char* definition_name = lua_tostring(L, -2);
+        lua_getfield(L, cgt, definition_name);
+        int depth = lua_tointeger(L, -1);
+        if (depth == level)
+          browse_definition(definition_name);
+        lua_pop(L, 1);  // depth of value
+        lua_pop(L, 1);  // value
+        // leave key on stack for next iteration
+      }
+    }
+    y += 2;
+  }
+
+  // unused functions
+  mvaddstr(y, 0, "                ");
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
     for (lua_pushnil(L); lua_next(L, t) != 0;) {
       const char* definition_name = lua_tostring(L, -2);
+      lua_getglobal(L, definition_name);
+      int is_function = lua_isfunction(L, -1);
+      lua_pop(L, 1);
       lua_getfield(L, cgt, definition_name);
-      int depth = lua_tointeger(L, -1);
-      if (depth == level)
+      if (is_function && lua_isnoneornil(L, -1))
         browse_definition(definition_name);
       lua_pop(L, 1);  // depth of value
       lua_pop(L, 1);  // value
       // leave key on stack for next iteration
     }
-    y += 2;
-  }
-
-  // unused functions
-  mvaddstr(y, 0, "                ");
-  for (lua_pushnil(L); lua_next(L, t) != 0;) {
-    const char* definition_name = lua_tostring(L, -2);
-    lua_getglobal(L, definition_name);
-    int is_function = lua_isfunction(L, -1);
-    lua_pop(L, 1);
-    lua_getfield(L, cgt, definition_name);
-    if (is_function && lua_isnoneornil(L, -1))
-      browse_definition(definition_name);
-    lua_pop(L, 1);  // depth of value
-    lua_pop(L, 1);  // value
-    // leave key on stack for next iteration
   }
 
   lua_settop(L, 0);