static vs dynamic dispatch

[markww]

Hi,

Can someone explain to me what static and dynamic dispatch are and what
the difference is between the two? Do this even occurr in C++?

Thanks

[Xeranic]

Re: static vs dynamic dispatch

The static and dynamic means the time to dispatch. The static dispatch
be determined at compile time, dynamic at runtime. In C++ dynamic
dispatch is implemented by using virtual function (or pointer to
function as c style).

On Dec 18, 8:13 am, "markww" <mar...@gmail.c omwrote:

Hi,
>
Can someone explain to me what static and dynamic dispatch are and what
the difference is between the two? Do this even occurr in C++?
>
Thanks

[markww]

Re: static vs dynamic dispatch

Hi Xeranic,

But what is 'dispatching'? What is being dispatched?

Thanks

Xeranic wrote:

The static and dynamic means the time to dispatch. The static dispatch
be determined at compile time, dynamic at runtime. In C++ dynamic
dispatch is implemented by using virtual function (or pointer to
function as c style).
>
On Dec 18, 8:13 am, "markww" <mar...@gmail.c omwrote:

Hi,

Can someone explain to me what static and dynamic dispatch are and what
the difference is between the two? Do this even occurr in C++?

Thanks

[Alf P. Steinbach]

Re: static vs dynamic dispatch

* markww:

Hi Xeranic,
>
But what is 'dispatching'? What is being dispatched?
>
Thanks
>
Xeranic wrote:

>The static and dynamic means the time to dispatch. The static dispatch
>be determined at compile time, dynamic at runtime. In C++ dynamic

Please don't top-post.

>dispatch is implemented by using virtual function (or pointer to
>function as c style).
>>
>On Dec 18, 8:13 am, "markww" <mar...@gmail.c omwrote:

>>Hi,
>>>
>>Can someone explain to me what static and dynamic dispatch are and what
>>the difference is between the two? Do this even occurr in C++?
>>>
>>Thanks

>

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Alan Johnson]

Re: static vs dynamic dispatch

markww wrote:

Hi,
>
Can someone explain to me what static and dynamic dispatch are and what
the difference is between the two? Do this even occurr in C++?
>
Thanks
>

In the context of C++, "dispatch" is just a fancy name for calling a
member function. A "static" dispatch is one where all the type
information needed to decide which function to call is known at compile
time. Consider the following example:

#include <iostream>

class A
{
public:
void f() const { std::cout << "A::f()" << std::endl ; }
} ;

class B
{
public:
void f() const { std::cout << "B::f()" << std::endl ; }
} ;

int main()
{
A a ;
B b ;

a.f() ;
b.f() ;
}

Here, the compiler has all the type information needed to figure out
which function "f" to call in each case. In the first call, A::f is
called, and in the second, B::f is called.

Dynamic dispatching is needed when it cannot be determined until runtime
which function to call. In C++, this is implemented using virtual
functions. Consider the following:

#include <iostream>

class base
{
public:
virtual void f() const = 0 ;
virtual ~base() {}
} ;

class A : public base
{
public:
virtual void f() const { std::cout << "A::f()" << std::endl ; }
} ;

class B : public base
{
public:
virtual void f() const { std::cout << "B::f()" << std::endl ; }
} ;

void dispatch(const base & x)
{
x.f() ;
}

int main()
{
A a ;
B b ;

dispatch(a) ;
dispatch(b) ;
}

The line "x.f() ;" gets executed twice, but a different function gets
called each time.

--
Alan Johnson

[markww]

Re: static vs dynamic dispatch


Alan Johnson wrote:

markww wrote:

Hi,

Can someone explain to me what static and dynamic dispatch are and what
the difference is between the two? Do this even occurr in C++?

Thanks

>
In the context of C++, "dispatch" is just a fancy name for calling a
member function. A "static" dispatch is one where all the type
information needed to decide which function to call is known at compile
time. Consider the following example:
>
#include <iostream>
>
class A
{
public:
void f() const { std::cout << "A::f()" << std::endl ; }
} ;
>
class B
{
public:
void f() const { std::cout << "B::f()" << std::endl ; }
} ;
>
int main()
{
A a ;
B b ;
>
a.f() ;
b.f() ;
}
>
Here, the compiler has all the type information needed to figure out
which function "f" to call in each case. In the first call, A::f is
called, and in the second, B::f is called.
>
Dynamic dispatching is needed when it cannot be determined until runtime
which function to call. In C++, this is implemented using virtual
functions. Consider the following:
>
#include <iostream>
>
class base
{
public:
virtual void f() const = 0 ;
virtual ~base() {}
} ;
>
class A : public base
{
public:
virtual void f() const { std::cout << "A::f()" << std::endl ; }
} ;
>
class B : public base
{
public:
virtual void f() const { std::cout << "B::f()" << std::endl ; }
} ;
>
void dispatch(const base & x)
{
x.f() ;
}
>
int main()
{
A a ;
B b ;
>
dispatch(a) ;
dispatch(b) ;
}
>
The line "x.f() ;" gets executed twice, but a different function gets
called each time.
>
--
Alan Johnson

Thanks Alan,

Mark