Re: tostring

Thank you very much, Nigel.  I missed the first line of section 8.4 of
the manual every time I read it which mentions that header file.

   With gratitude,
   Ken

On Thu, Jul 8, 2010 at 3:44 PM, Nigel Atkinson <[email protected]> wrote:
> Hi Ken,
>
> Add #include "luabind/operator.hpp"
>
> after you include the main luabind header, in your case line 4.
>
> That makes your program work - I tested it out on Linux (gcc 4.4.3).
>
> In the past I found that I needed to prototype the operator << function
> before including operator.hpp, but now that seems to be not needed now.
>
> Nigel
>
> On Thu, 2010-07-08 at 09:59 -0700, Ken Smith wrote:
>
> I'm having a problem mapping an operator<< to tostring for my class.
> My environment is GCC 4.0 on Mac OS X 10.4+.  Here is the code.
>
>  1 #include <iostream>
>  2
>  3 #include "lua.hpp"
>  4 #include "luabind/luabind.hpp"
>  5
>  6 struct test_t
>  7 {
>  8     test_t(const std::string& name)
>  9         :
>  10             name_(name)
>  11     {
>  12     }
>  13     friend std::ostream& operator<<(
>  14         std::ostream& os, const test_t& test
>  15     );
>  16
>  17 private:
>  18     std::string name_;
>  19 };
>  20
>  21 std::ostream& operator<<(std::ostream& os, const test_t& test)
>  22 {
>  23     os
>  24         << "test_t: "
>  25         << test.name_;
>  26
>  27     return os;
>  28 }
>  29
>  30 int main()
>  31 {
>  32     lua_State* L = luaL_newstate();
>  33     luaL_openlibs(L);
>  34     using namespace luabind;
>  35     open(L);
>  36     module(L)
>  37     [
>  38         class_<test_t>("test_t")
>  39             .def(constructor<const std::string&>())
>  40             .def(tostring(self))
>  41     ];
>  42     if (luaL_dostring(L, "t = test_t('hi') print(t)") == 1)
>  43     {
>  44         std::cout
>  45             << "Couldn't run Lua program: "
>  46             << lua_tostring(L, -1)
>  47             << std::endl;
>  48     }
>  49
>  50 }
>
> Compiling this yields the following error.
>
> src/main.cpp:40: error: 'self' was not declared in this scope
> src/main.cpp:40: error: 'tostring' was not declared in this scope
>
> Commenting out line 40 causes the sample to compile but of course, the
> call to print(t) fails with:
>
> Couldn't run Lua program: No such operator defined
>
> How should I change this example to map test_t's operator<< to its
> __tostring metamethod in Lua?
>
>   Regards,
>   Ken
>
> ps. Apologies if you receive two copies of this mail.  I was not
> subscribed to the list when I sent it the first time.
>
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