C++ class member pointer to global function

Question

I want to have a class which has as a member a pointer to a function

here is the function pointer:

typedef double (*Function)(double);

here is a function that fits the function pointer definition:

double f1(double x)
{
    return 0;
}

here is the class definion:

class IntegrFunction
{
public:
    Function* function;
};

and somewhere in the main function i want to do something like this:

IntegrFunction func1;
func1.function = f1;

But, this code does not work.

Is it possible to assign to a class member a function pointer to a global function, declared as above? Or do I have to change something in the function pointer definition?

Thanks,

How does it "not work"? Do you get a compiler error? If so, what is it? — Billy ONeal
– Billy ONeal, Commented May 14, 2011 at 21:58
The answer might be easier for us to find if you would supply a complete example. You are so close, it would only take just a few more lines to make it complete. Also, can you tell us what you mean by "does not work?" Do you get an error from the compiler? Linker? Do you get a run-time behavior different than what you expect? — Robᵩ
– Robᵩ, Commented May 14, 2011 at 21:59

Robᵩ · Accepted Answer · 2011-05-14 22:01:46Z

9

Replace this:

class IntegrFunction
{
public:
    Function* function;
};

with this:

class IntegrFunction
{
public:
    Function function;
};

Your typedef already creates a pointer-to-function. Declaring Function* function creates a pointer-to-pointer-to-function.

answered May 14, 2011 at 22:01

Robᵩ

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1 Comment

Alina Danila Over a year ago

Thanks, I understood my mistake and my code works now. I should be more careful next time.

Slava Semushin · Accepted Answer · 2011-05-14 22:03:12Z

4

Just replace

Function* function;

to

Function function;

answered May 14, 2011 at 22:03

Slava Semushin

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Comments

Christian Rau · Accepted Answer · 2011-05-14 22:04:02Z

2

You declare the variable as Function* function, but the Function typedef is already a typedef for a pointer. So the type of the function pointer is just Function (without the *).

answered May 14, 2011 at 22:04

Christian Rau

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Comments

Johannes Schaub - litb · Accepted Answer · 2011-05-15 11:05:54Z

0

Replace

typedef double (*Function)(double);

by

typedef double Function(double);

to typedef the function-type. You can then write the * when using it.

answered May 15, 2011 at 11:05

Johannes Schaub - litb

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Comments

Puppy · Accepted Answer · 2011-05-14 21:58:16Z

-3

You need to use the address-of operator to obtain a function pointer in Standard C++03.

func1.function = &f1;

answered May 14, 2011 at 21:58

Puppy

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1 Comment

James McNellis Over a year ago

No you don't. The & is necessary for taking the address of a member function but not for a nonmember function.

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