CODEWITHSUNDEEP
c++function
FXisME
FXisME

Reputation: 31

Address of bound member function

I have a the following member function:

void GClass::InitFunctions()
{ // Initialize arrays of pointers to functions.

ComputeIntLen[0] = &ComputeILS;
ComputeIntLen[1] = &ComputeILE;
ComputeIntLen[2] = &ComputeILI;
PostStep[0] = &PSS;
PostStep[1] = &PSE;
PostStep[2] = Ψ
gRotation = new Rotation();
}

GClass obviously contains all the relevant members -:

    void ComputeILE(Int_t, Int_t *, Double_t *);
    void ComputeILI(Int_t, Int_t *, Double_t *);
    void PSS(Int_t , Int_t *, Int_t &, Int_t*);
    void PSE(Int_t, Int_t *, Int_t &, Int_t*);
    void PSI(Int_t , Int_t *, Int_t &, Int_t*);
    ComputeIntLenFunc ComputeIntLen[gNproc];
    PostStepFunc      PostStep[gNproc];
... //other members
}

where gNproc is a global const int and ComputeIntLenFunc and PostStepFunc are typedefs like this:

typedef void (*ComputeIntLenFunc)(Int_t ntracks, Int_t *trackin, Double_t *lengths);
typedef void (*PostStepFunc)(Int_t ntracks, Int_t *trackin, Int_t &nout, Int_t* trackout);

When I Compile this I get gcc gives an error: "ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say ‘&GClass::ComputeIntLenScattering’ "

When I replace FunctionNames by GClass::FunctionNames in InitFunctions() I get "cannot convert ‘void (GClass::*)(Int_t, Int_t*, Double_t*)’ to ‘void (*)(Int_t, Int_t*, Double_t*)’ in assignment"

Please help me. What topic of C++ is this ?

Upvotes: 3

Views: 4575

Answers (2)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361482

Non-static member function pointer is different from free function pointer. What you're using is basically free function pointer types, which would not work, as type of &GClass::ComputeILS is incompatible with ComputeIntLenFunc.

Use this:

typedef void (GClass::*ComputeIntLenFunc)(Int_t, Int_t *, Double_t *);
typedef void (GClass::*PostStepFunc)(Int_t, Int_t *, Int_t &, Int_t*);

I omitted the parameter names, as they're not required in the typedefs.

Also, you've to use GClass:: when you get the address of member functions:

ComputeIntLen[0] = &GClass::ComputeILS;
ComputeIntLen[1] = &GClass::ComputeILE;
ComputeIntLen[2] = &GClass::ComputeILI;
PostStep[0] = &GClass::PSS;
PostStep[1] = &GClass::PSE;
PostStep[2] = &GClass::PSI;

The error message says this very clearly:

ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say ‘&GClass::ComputeIntLenScattering

Upvotes: 2

Andre
Andre

Reputation: 1607

You need to prepend the class to your typedefs as well:

typedef void (GClass::*ComputeIntLenFunc)(Int_t ntracks, Int_t *trackin, Double_t *lengths);
typedef void (GClass::*PostStepFunc)(Int_t ntracks, Int_t *trackin, Int_t &nout, Int_t* trackout);

Then your (first) type will mean: this is a pointer to a member function in class GClass which takes an Int_t, an Int_t* and so forth whereas in your version it just referred to a free function with the same parameters.

Upvotes: 1

Related Questions