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i've just been reading some various documentation and forums and what not for interesting ways of doing things, and i've stumbled upon a syntax i've straight up never seen before. can someone tell me what the heck this means?

C++
std::vector <base *(*)()>  vectorArray;


i've been using vectors in many of my programs, but i've never seen something like this done before. apparently it allows you store a function call in it, and then, based on whatever iterator that function call is at, you just go:

C++
vectorArray[0] ();


and it calls whatever function you put there. This seems like an excellent way to call constructors for various derived classes, so you can just make an iterator synonymous with a certain class, shoot use a map even :P, but use it to call the constructor for a derived class and store it an a pointer to the base class, but the syntax is so foreign to me, i'm tentative as to whether it's safe to use it or not. i'd really like to :P so, in summary, my question is, what is this doing, how is it doing it, is this operation specific to vectors or general to c and c++ arrays, and is it safe to use it?
Posted
Updated 10-Oct-11 15:00pm
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Stefan_Lang 11-Oct-11 6:13am     CRLF
an excellent way to call constructors Nope. Constructors are class methods and method function pointers require a different syntax. The syntax you posted only works for global functions.
FatalCatharsis 11-Oct-11 10:06am     CRLF
oh sorry, i didn't explain fully, i meant something like this :P. template < class T> base * createT() {return new T;} vector<base*(*) () > functionStore; and then you just store the template function with the template argument of a specific derived class like: functionStore.push_back(&createT<derived1>); functionStore.push_back(&createT<derived2>); etc, and then call them at runtime based on some argument that would be the corresponding indice, like if input is 0 then call functionStore[0] (); and create that specific object and store it in a pointer of the base class. polymorphic awesomeness! :P. i was stepping ahead of myself when stating all that :P
Ali Fakoor 12-Oct-11 7:10am     CRLF
If you want it more safe (i.e: peaceful), better to typedef the input type for vector template as <pre> typedef base *(*BaseCreatorFuncType)() std::vector <BaseCreatorFuncType> vectorArray; </pre> See also the points 33.5 and 33.6 in http://www.parashift.com/c++-faq-lite/pointers-to-members.html#faq-33.5 and http://www.parashift.com/c++-faq-lite/pointers-to-members.html#faq-33.6 They are described for c++ and pointer to methods but they well apply to function pointers as well.
Philippe Mori 12-Oct-11 23:32pm    
There is no new syntax in that... That syntax would work with compiler more than 10 years old.
FatalCatharsis 13-Oct-11 10:10am    
whoa whoa, didn't mean, "new syntax to c++", i meant, "new syntax to me" :\ . I'm relatively new to programming, and i've never seen anything like this, i didn't really know what to google to find information on it. Shoot, when i first saw it, i didn't even know that a function was involved with it, i thought it was just trying to dereference a pointer to a pointer in a weird way or something stupid like that. now, after reading this, i google pointer to a function, and it's all over the place :P . So, uh, sorry if this was a stupid question.

base *(*)() - pointer to a function which returns a type 'base*'. So, vectorArray can take functions of type base* Fun() as its elements.
 
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FatalCatharsis 11-Oct-11 9:32am    
and this is just something that i coulda been doing forever ago, pointers to functions?!? god, that seems so incredibly useful. Mkay, i know what i'm gonna be experimenting with for awhile :P. thanks
C++
base *(*)()

is the syntax for a pointer to a function which returns a pointer to base; so your vector will contain pointers to functions.
 
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