[Boost-users] dynamic modules was Re: [preprocessor]:issues with expansion.

Subject: [Boost-users] dynamic modules was Re: [preprocessor]:issues with expansion.
From: Littlefield, Tyler (tyler_at_[hidden])
Date: 2012-12-20 13:44:14

hello:
Thanks for the info. What you said makes sense, I should've thought more 
before I went with it.
Essentially here's what I'm trying to do--perhaps someone knows a better 
way to do this.
Right now when I install a module in this system I'm working on, I have 
to add a #include to the top, and then something like 
RegisterModule<TileEngine>(); or something similar.
I wanted a way to do something like call REGISTER_MODULE from the 
TileEngine.h so that it would be dynamically added in at compile-time, 
rather than having to hard-code the includes and registrations into the 
system.
If there's a way with boost to do this at compile-time so that there is 
no need to hard-code it (excluding shared libraries), I'd apreciate any 
information.
Thanks,
On 12/19/2012 11:47 PM, Nathan Ridge wrote:
>> Date: Wed, 19 Dec 2012 20:13:23 -0800
>> From: jeffrey.hellrung_at_[hidden]
>> To: boost-users_at_[hidden]
>> Subject: Re: [Boost-users] [preprocessor]:issues with expansion.
>>   
>> On Wed, Dec 19, 2012 at 3:58 PM, Littlefield, Tyler
>> <tyler_at_[hidden]<mailto:tyler_at_[hidden]>> wrote:
>> hello all:
>> I have the following code:
>> #define REGISTER_MODULE(module)(\
>> #ifdef BOOST_PP_EQUAL(BOOST_PP_LIST_SIZE(MODULES), 0)\
>> //there are currently no modules in the list.
>> #define MODULES((module), BOOST_PP_NIL)
>> #else
>> BOOST_PP_LIST_APPEND(MODULES, module)\
>> #endif
>> )
>>   
>> I am somewhat of a newb at preprocessor magic, so any advice would be
>> useful. For whatever reason this translates out to 'module)' when I try
>> to compile it with -E -P.
>> The idea is that it will add to the modules list (assuming the modules
>> list exists) the module to be registered, which should just be a type.
>> Thanks,
>>   
>> Someone can correct me here, but I believe you can't use preprocessor
>> directives (#define, #if, etc.) within a macro definition, and, well,
>> who knows what'll happen if you try :/
>>   
>> - Jeff
> Right, and to address your desired use case a little more specifically,
> I don't think you can store state in the preprocessor in between macro
> invocations (if I'm wrong, please correct me, I would find such an
> ability very useful as well).
>
> Regards,
> Nate
>   		 	   		
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-- 
Take care,
Ty
http://tds-solutions.net
The aspen project: a barebones light-weight mud engine:
http://code.google.com/p/aspenmud
He that will not reason is a bigot; he that cannot reason is a fool; he that dares not reason is a slave.