Lua C++ Table Iteration -

i having slight confusion of how lua_next works. user defines table:

a={["a1"]=20,["a2"]=30} 

i want print table c++ code:

inline int lua_print(lua_state* l) { wxstring wxreturnstr=wxemptystring; wxstring tempstring=wxemptystring; int nargs = lua_gettop(l);  (int i=1; <= nargs; i++) {     int type = lua_type(l, i);     switch (type)     {      case lua_tnil:         break;      case lua_tboolean:         tempstring<<(lua_toboolean(l, i) ? "true" : "false");         break;      case lua_tnumber:         tempstring<<lua_tonumber(l, i);         break;        case lua_tstring:           tempstring<<lua_tostring(l, i);         break;       case lua_ttable:       {           lua_pushnil(l);           while(lua_next(l,-2))           {                 const char* key=lua_tostring(l,-2);                 double val=lua_tonumber(l,-1);                 lua_pop(l,1);                 tempstring<<key<<"="<<val<<"\t";           }            break;       }        default:           tempstring<<lua_typename(l, type);         break;     }      wxreturnstr=wxreturnstr+tempstring+"\n";     tempstring=wxemptystring;  }  lua_pop(l,nargs); 

this code works when call lua:

print(a) -- works 

however, imagine have table in lua as:

b={["b1"]=10, ["b2"]=15} 

if call code as:

print(a,b) -- twice prints contents of b  

my understanding how lua_next work in following figure: [edition #1]

where bug?

the bug in lua_next(l, -2) line, because -2 refers stack top minus one, happens here last argument print.

use lua_next(l, i) instead.

upd: lua stack indexes subject float when moving code around @ development stage, general advice pin indexes sml int t = lua_gettop(l) after getting/pushing/considering values , use t instead of -n (though specific case appears sort of keystroke bug.)