Re: use of gettop to change functionality

[Tony Finch <dot@...>]

On Tue, 1 Mar 2011, Gunnar Zötl wrote:
>
> > foo(nil,nil,nil) should be the same as foo(nil,nil) and foo() etc
>
> Nope, it should not. Passing three nils is not the same as passing
> nothing at all.

Lua works much more consistently when nil is treated the same as the
absence of a value.

table.insert() should have its two-argument form separated out into a
table.append() function - which could quite nicely append multiple values.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
Fisher: Variable 3 or 4, becoming southwesterly 4 or 5 in north. Mainly
slight. Fair. Moderate or good.


diff --git a/src/ltablib.c b/src/ltablib.c
index faabfe5..a425b39 100644
--- a/src/ltablib.c
+++ b/src/ltablib.c
@@ -45,27 +45,25 @@ static int maxn (lua_State *L) {
 #endif


+static int tappend (lua_State *L) {
+  int n = aux_getn(L, 1);  /* length of array */
+  int i = n + lua_gettop(L) - 1;  /* plus number of args excluding array */
+  while (i > n)
+    lua_rawseti(L, 1, i--);  /* t[i] = v */
+  return 0;
+}
+
+
 static int tinsert (lua_State *L) {
   int e = aux_getn(L, 1) + 1;  /* first empty element */
-  int pos;  /* where to insert new element */
-  switch (lua_gettop(L)) {
-    case 2: {  /* called with only 2 arguments */
-      pos = e;  /* insert new element at the end */
-      break;
-    }
-    case 3: {
-      int i;
-      pos = luaL_checkint(L, 2);  /* 2nd argument is the position */
-      if (pos > e) e = pos;  /* `grow' array if necessary */
-      for (i = e; i > pos; i--) {  /* move up elements */
-        lua_rawgeti(L, 1, i-1);
-        lua_rawseti(L, 1, i);  /* t[i] = t[i-1] */
-      }
-      break;
-    }
-    default: {
-      return luaL_error(L, "wrong number of arguments to " LUA_QL("insert"));
-    }
+  int i;
+  int pos = luaL_checkint(L, 2);  /* where to insert new element */
+  if (lua_gettop(L) != 3)
+    return luaL_error(L, "wrong number of arguments to " LUA_QL("insert"));
+  if (e < pos) e = pos;  /* `grow' array if necessary */
+  for (i = e; i > pos; i--) {  /* move up elements */
+    lua_rawgeti(L, 1, i-1);
+    lua_rawseti(L, 1, i);  /* t[i] = t[i-1] */
   }
   lua_rawseti(L, 1, pos);  /* t[pos] = v */
   return 0;
@@ -264,6 +262,7 @@ static int sort (lua_State *L) {


 static const luaL_Reg tab_funcs[] = {
+  {"append", tappend},
   {"concat", tconcat},
   {"foreach", deprecatedfunc},
   {"foreachi", deprecatedfunc},