pointer to member function

[sarmadys]

Hello,

I am trying to use "remove_if" with a predicate function inside a class. The code intends to remove the grid cells which an agent cannot move into (from among all possible cells).

void classname::function1()
{
vector<MoorePoint> neighbors;
....
neighbors.erase(std::remove_if(neighbors.begin(),neighbors.end(),&classname::cannotMoveIn), neighbors.end()); 
...
}

bool classname::cannotMoveIn(MoorePoint mp)
{
    return !mp.inGridNotOccupied;
}

That code would work if it was not in a class and the predicate was not a member function. However, now I receive long error messages which I guess refer to incompatibility of remove_if template with the predicate parameter (one error includes : error C2064: term does not evaluate to a function taking 1 arguments).

Does anyone have any idea what is wrong?

Thanks.

[MrViggy]

Use one of the std :: mem_fun adaptors:

http://www.sgi.com/tech/stl/mem_fun_t.html
http://www.sgi.com/tech/stl/mem_fun_ref_t.html

Viggy

[D_Drmmr]

That code would work if it was not in a class and the predicate was not a member function. However, now I receive long error messages which I guess refer to incompatibility of remove_if template with the predicate parameter (one error includes : error C2064: term does not evaluate to a function taking 1 arguments).

That's because member functions have an implicit first argument, which is the this pointer. So, to call a member function, you need an instance of the class to call it on.

Given that your function does not use any class members you can also make the function a static member, or use a global function (possibly in an anonymous namespace), or use locally defined function object - see below -, or use a lambda function if your compiler supports it.

void classname::function1()
{
    vector<MoorePoint> neighbors;
    //....
    struct {
        bool operator ()(const MoorePoint& mp) const {
            return !mp.inGridNotOccupied;
        }
    } cannotMoveIn;
    neighbors.erase(std::remove_if(neighbors.begin(), neighbors.end(), cannotMoveIn), neighbors.end()); 
}