std::list::remove_if Problem.

[Ptlomej]

I got a little problem with using std::list::remove_if in a Class the problem is I need the function in the class. If the function are not in the class its works but i cant Destroy the Body and I need it in there to get the world.

The code.

Code: [Select]


bool Map::RemoveStructure(Structure *TheStructure){
if(TheStructure->ThisType == 2){
ThisWorld->DestroyBody(TheStructure->StructureBody);
}
return TheStructure->Remove;
}
void Map::RenderMap(sf::RenderWindow* Window){
if(sMapName.length() > 0){
for(list<Structure*>::iterator IT = StructureList.begin(); IT != StructureList.end(); IT++){
Window->Draw((*(*IT)->StructureShape));
}
StructureList.remove_if(&Map::RemoveStructure);
}
}


The error.

Code: [Select]


1>C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\list(1218): error C2064: Ausdruck ergibt keine Funktion, die 1 Argumente übernimmt


I hope you can help my
Your,
Jason

[Laurent]

A member function needs an instance of the class to be called, remove_if won't be able to call Map::RemoveStructure all alone

You should have a look at boost/std::bind if you can. Or std::bind1st / std::memfun (don't remember if you need both) if you can't use boost or C++11.

[Ptlomej]

memfun and bin1st dont work :S the same error
i dont use boost only Box2D and SFML

or how to use this functions ? it can be that i use it wrong

[Laurent]

Code: [Select]

remove_if(std::bind1st(std::mem_fun(&Map::RemoveStructure), this));
Not tested

the same error

An english translation would be welcome.

[Ptlomej]

Code: [Select]

Ausdruck ergibt keine Funktion, die 1 Argumente übernimmt

hmm google translator say

Code: [Select]

Expression is not a function that takes an argument

Code: [Select]

remove_if(std::bind1st(std::mem_fun(&Map::RemoveStructure), this));
Not tested

I think "this" is not the variable waht i want to give with ? its the Pointer to Structure or not ?

[Ptlomej]

With using this in Boost

Code: [Select]

StructureList.remove_if(boost::bind(boost::mem_fn(&Map::RemoveStructure)));

I get again a Error

1>C:\....\.....\.....\Include\boost/bind/bind.hpp(182): error C2064: Ausdruck ergibt keine Funktion, die 0 Argumente übernimmt

[Laurent]

I think "this" is not the variable waht i want to give with ? its the Pointer to Structure or not ?

In the end the function to call is:

Code: [Select]

bool b = this->RemoveStructure(item);
std::memfun transforms it to a regular (non-member) function call:

Code: [Select]

bool b = RemoveStructure(this, item);
And you need to fix the first argument with std::bind1st so that the final call is:

Code: [Select]

bool b = RemoveStructure(item);
... and this one is compatible with what std::list::remove_if expects.

With boost:

Code: [Select]

StructureList.remove_if(boost::bind(&Map::RemoveStructure, this, _1));

By the way, are you actually destroying the structure in your function? It should only be a predicate, ie. return a boolean indicating whether the item should be removed or not. It must not have any side-effect.

[Ptlomej]

Thank you

is BOOST_FOREACH faster as a std for with iterator ?
or waht is the fastest way to run trough a list?

[Laurent]

is BOOST_FOREACH faster as a std for with iterator ?

BOOST_FOREACH is a convenience macro, it just hides the iterator-based loop.

waht is the fastest way to run trough a list?

There's only one way, with iterators.

[Ptlomej]

Okay thank you for all

and.. Nice Library SFML 2 is very nice

when i find any that could be change or add
i will take up a request

Closed!