function pointer inside class

Question

I need a switch for different functions to circumvent frequent if-directions. It should work similar to the following code, encapsulated in a class:

#include<iostream>
#include<stdlib.h>

using namespace std;

template<class T>
class MaxSwitch
{
public:
typedef T (MaxSwitch::*Max_P)(T,T);
Max_P fooC_P;

MaxSwitch(int Q) {
    if (Q==0)fooC_P=&MaxSwitch::MaxVal1;
    else fooC_P=&MaxSwitch::MaxVal2;
}

inline T MaxVal1(T kx,T MAX)
{
    return kx+1;
}

inline T MaxVal2(T kx,T MAX)
{
    return MAX;
}

};

 int main( int argc, char ** argv )
{
int Q=atoi ( argv[1] );
MaxSwitch<int> MAXSW(Q);


int MAX=5;

for ( int kx=0;kx<MAX;kx++ ) for ( int ky=0;ky<(MAXSW.fooC_P)(kx,MAX);ky++ )
    {
        cout<<"(kx="<<kx<<", ky="<<ky<<endl;
    }

return 0;
 }

I have now the trivial problem that the function call (MAXSW.fooC_P)(ky,MAX) is wrong. How to do it properly?

a quick note: your naming convention for parameters makes the code not that readable.. — Jay D
– Jay D, Commented May 19, 2012 at 8:35
(Jay D is being nice with "not that readable" - I'd have said completely confusing.) — Mat
– Mat, Commented May 19, 2012 at 8:36

Mat · Accepted Answer · 2012-05-19 08:32:01Z

6

MAXSW.fooC_P is the pointer-to-member-function that you need to call, and MAXSW is the object you want to call it on. So you can call that function with:

(MAXSW.*(MAXSW.fooC_P))(ky,MAX);

answered May 19, 2012 at 8:32

Mat

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1 Comment

Mankarse Over a year ago

Note that (MAXSW.*MAXSW.fooC_P)(ky,MAX) will also work (that is - the inner brackets are redundant).

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