Hello.
If I was to call a method of class T, M for each element in a collection,
I'd do it like this:
vector<int> vec;
....
for_each(vec.be gin(), vec.end(), mem_fun_ref(&T: :M));
Okay, I can see that mem_fun_REF makes it obvious that I must use a
reference, but why? Is it not possible to pass a function by-reference? As I
see it, T::M is being passed as a pointer here.
void func(int& val); func(12); << reference
void func(int* val); int val = 12; func(&val); << pointer
//Anders
2  3502  Hello.
If I was to call a method of class T, M for each element in a collection,
I'd do it like this:
vector<int> vec;
...
for_each(vec.be gin(), vec.end(), mem_fun_ref(&T: :M));
Okay, I can see that mem_fun_REF makes it obvious that I must use a
reference, but why? Is it not possible to pass a function by-reference?
No, you can only pass the address. As I see it, T::M is being passed as a pointer here.
The REF, in mem_fun_ref, refers to the argument type( of T::M ), which
will be passed to the function call operator.
void func(int& val); func(12); << reference
void func(int* val); int val = 12; func(&val); << pointer
//Anders
On Mon, 30 Jun 2003 22:34:24 +0200, "Anders" <gr*******@adsl home.dk>
wrote: Hello.
If I was to call a method of class T, M for each element in a collection,
I'd do it like this:
vector<int> vec;
...
for_each(vec.b egin(), vec.end(), mem_fun_ref(&T: :M));
That can't be legal - you can't call a T member function on an int
reference.
Okay, I can see that mem_fun_REF makes it obvious that I must use a
reference, but why? Is it not possible to pass a function by-reference? As I
see it, T::M is being passed as a pointer here.
void func(int& val); func(12); << reference
void func(int* val); int val = 12; func(&val); << pointer
The ref refers to the the fact that the object passed as the first
argument of the functor must be a reference. e.g.
T t;
mem_fun_ref(&T: :M)(t); //pass T reference
mem_fun(&T::M)( &t); //pass T pointer
so in practice you use mem_fun_ref for containers like:
vector<T>
and mem_fun for containers like:
vector<T*>
Tom This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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