Re: _call me, please

["Mauro Iazzi" <mauro.iazzi@...>]

Call lua_setmetatable and everything should work.

On 20/03/2008, Foreman, Bill <billf@akelainc.com> wrote:
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> Need help,
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> I have a built-in module for complex numbers defined as follows:
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>
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> int complex_number_new(lua_State* L)
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> {
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>       // make a complex number and put it on the stack
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>       return 1;
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> }
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> static const struct luaL_Reg s_complex_f[] =
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> {
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>       // constructor
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>       { "new", complex_number_new },
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>
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>       // many more functions …
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>       { 0, 0 }
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> };
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> static const struct luaL_Reg s_complex_m[] =
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> {
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>       { "__call", complex_number_new },
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>
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>       // many more operators …
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>       { 0, 0 }
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> };
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> int luaopen_complex_number(lua_State* L)
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> {
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>       //
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>       luaL_newmetatable(L, "ak_complex");
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>
>
>       //
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>       luaL_register(L, 0, s_complex_m);
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>       luaL_register(L, "complex", s_complex_f);
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>       return 1;
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> }
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> Question:  Why do I get the error "attempt to call global 'complex' (a table
> value)" when I attempt x = complex (1, 2), which should return the same
> thing as complex.new(1, 2)?
>
>
>
> I see this question in the forum, but I (for the life of me) don't
> understand the responses.  What is special about __call, and why isn't it
> better documented?  I am so thick that it is going to take a concrete
> example in c or c++ to breach the wall.
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>
>
> What does work is
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> setmetatable(complex, { __call = function( _, ... ) return complex.new( ...
> ) end })
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> but I want to do this internally, not in Lua.
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>
>
> --BillF