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[theman515]

Hello everyone, I have sort of an odd question. Is there any way in C++ to make a string into a keyword through pre-processor macros? For example I know this is possible

Code:

#define str(x) #x

and that makes x a string, even though it's a keyword into a string. I was wondering if the reverse is possible. thanks in advance 

[eigenbom]

I'm pretty sure that's impossible. What's the use case for this?

[increpare]

That only works if x is a constant string that's known at compile time.  If you want to turn string in general into language keywords at runtime, then you're asking for a full language interpreter/compiler (basically not practical if you want to use c++). If you want to access variables by name, then you're looking for some sort of reflection or rtti (probably the more useful search word for c++).   Enabling this in the compiler may slow some things down, can't remember, but it allows you to access things about classes from strings.

If you're just interested in compile-time stuff, I ... don't think it's possible.

I'll second eigenbom's request that you give us a hint what you want this for

[theman515]

hmm that reflection or rtti thing sounds like what I need.

What I need it for is that I want a developers console for my game and the ability to change class members through string commands. I could just do however many if statements but that seems like a lot of work for something so procedure like.

[increpare]

hmm that reflection or rtti thing sounds like what I need.

What I need it for is that I want a developers console for my game and the ability to change class members through string commands. I could just do however many if statements but that seems like a lot of work for something so procedure like.

yep, rtti to the rescue   (or, if you wanted to do fancy stuff, a proper scripting language binding, but probably overkill for your purposes...)

[theman515]

alright, thanks again guys.  and yeah I tried boost::python for that but bjam was waaayyyy too complex for my purposes.

[eigenbom]

Yeh that's a hard thing to do in a compiled language, because variable names get transformed into addresses. The actual names get thrown away.

I'm not sure you can do what you want to with RTTI. You might be able to automate it by compiling with debugging symbols on, then hooking into a debugger. But that is icky..

Probably the simplest approach for now is just to have a big function that maps from string to variable reference, with a bunch of switches, but eventually you'll want to move to a scripting language, or a component-based approach..

[theman515]

any advice for the scripting language for using classes? python doesnt seem very... simple to integrate classes in to.

[eigenbom]

Lua. best programming investment you'll ever make.

[eigenbom]

+ Luabind

[mcc]

I did this using lua.

In general though if this is the kind of thing you want to do, writing your game in C++ to start with may not be the best approach.

[bateleur]

Another tip: Depending on how many classes you need to do this to, it's often easier to just write yourself debug helper methods for your classes.

[xrabohrok]

I'm taking a 300 level college class about just this right now.  Not easy stuff.  You might want to consider making a static method class, something that doesn't need to be instantiated but collects together recurring useful functions.  Just a thought.