Differences

This shows you the differences between two versions of the page.

--- lua:lua [2008/09/01 15:41] – deva
+++ lua:lua [2012/04/20 11:57] – deva
@@ Line 1: / Line 1: @@
 =====LUA=====
-====c/c++====
+====C/C++====
+===Arrays===
 <code lua>
 myarray = {1,2,3};
@@ Line 8: / Line 9: @@
 <code c>
 lua_createtable(L, 0, 3);
-int top = gettop(L);
+int top = lua_gettop(L);
 // add '1' to the list
 lua_pushinteger(L, 1);
@@ Line 20: / Line 21: @@
 // and then some code to bind it to "myarray"
+</code>
+===Array of arrays===
+An array with 10 entries each containing 2 entries:
+<code>
+  int num = 10;
+  int sz = 2;
+  lua_createtable(L, num * sz, 0);
+  int toptop = lua_gettop(L);
+  for(int i = 1; i <= num; i++) {
+    lua_createtable(L, 0, sz);
+    int top = lua_gettop(L);
+    for(int j = 1; j <= sz; j++) {
+      char buf[10];
+      sprintf(buf, "%d-%d", i, j);
+      lua_pushstring(L, buf);
+      lua_rawseti(L, top, j);
+    }
+    lua_rawseti(L, toptop, i);
+  }
+  return 1;
+</code>
+===Fields (maps)===
+<code lua>
+foo = {}
+foo.hello = 'world'
+foo.bar = {}
+foo.bar.ping = 'pong'
+foo.bar.bas = {}
+foo.bar.bas.ding = 'ring'
+</code>
+Corresponds to:
+<code c>
+int foo, bar, bas;
+// Create global 'foo'
+lua_newtable(L);
+lua_setglobal(L, "foo");
+// Set foo.hello = 'world'
+lua_getglobal(L, "foo");
+foo = lua_gettop(L);
+lua_pushstring(L, "world");
+lua_setfield(L, foo, "hello");
+// Create 'bar' in 'foo'
+lua_getglobal(L, "foo");
+foo = lua_gettop(L);
+lua_newtable(L);
+lua_setfield(L, foo, "bar");
+// Set foo.bar.ping = 'pong'
+lua_getglobal(L, "foo");
+foo = lua_gettop(L);
+lua_getfield(L, foo, "bar");
+bar = lua_gettop(L);
+lua_pushstring(L, "pong");
+lua_setfield(L, bar, "ping");
+// Create 'bas' in 'foo.bar'
+lua_getglobal(L, "foo");
+foo = lua_gettop(L);
+lua_getfield(L, foo, "bar");
+bar = lua_gettop(L);
+lua_newtable(L);
+lua_setfield(L, bar, "bas");
+// Set foo.bar.bas.ding = 'ring'
+lua_getglobal(L, "foo");
+foo = lua_gettop(L);
+lua_getfield(L, foo, "bar");
+bar = lua_gettop(L);
+lua_getfield(L, bar, "bas");
+bas = lua_gettop(L);
+lua_pushstring(L, "ding");
+lua_setfield(L, bas, "ring");
+lua_pop(L, 1); // pop 'foo' off the stack.
 </code>