mem_fun vs mem_fun_ref [英] mem_fun vs mem_fun_ref
问题描述
mem_fun和mem_fun_ref之间的确切区别是什么，因为在
我看过的所有例子中，它们的使用方式完全相同？
-
Ioannis Vranos
http： //www23.brinkster.com/noicys
What is the exact difference between mem_fun and mem_fun_ref, since in
all examples I looked at, they are used in exactly the same way?
--
Ioannis Vranos
http://www23.brinkster.com/noicys
推荐答案
" Ioannis Vranos" < iv*@remove.this.grad.com>写了...
"Ioannis Vranos" <iv*@remove.this.grad.com> wrote...
mem_fun和mem_fun_ref之间的确切区别是什么，因为在我看过的所有示例中，它们的使用方式完全相同？
What is the exact difference between mem_fun and mem_fun_ref, since in all
examples I looked at, they are used in exactly the same way?
他们返回不同类型的对象，mem_fun_t和mem_fun_ref_t，
其成员函数operator（）依次采用不同的参数，
前者需要T *，后者需要T&。 RTFM。
V
They return objects of different types, mem_fun_t and mem_fun_ref_t,
whose member functions operator(), in turn, take different arguments,
the former takes T*, the latter takes T&. RTFM.
V
Ioannis Vranos写道：
Ioannis Vranos wrote:
mem_fun和mem_fun之间的确切区别是什么？ mem_fun_ref，因为在我看过的所有例子中，它们的使用方式完全相同？
What is the exact difference between mem_fun and mem_fun_ref, since in
all examples I looked at, they are used in exactly the same way?
mem_fun返回一个可以用指针调用的对象到一个
对象; mem_fun_ref返回一个可以使用对象
或对象引用调用的对象。像这样：
#include< functional>
#include< iostream>
使用std :: mem_fun;使用std :: mem_fun_ref;
使用std :: cout;
struct S
{
void f（）
{
cout<< 叫做S :: f\ n;
}
};
int main（）
{
S s;
S * sp =& s;
mem_fun（& S :: f） （sp）;
mem_fun_ref（& S :: f）（s）;
返回0;
}
TR1'的mem_fn并不需要这个早期的决定; mem_fn（& S :: f）可以用一个对象，一个对象的引用，一个指向对象的指针，一个指向一个对象的指针，或者一个指向一个对象的智能指针来调用$ b $对象。
-
Pete Becker
Dinkumware，Ltd。（ http://www.dinkumware.com ）
Ioannis Vranos写道：
Ioannis Vranos wrote:
mem_fun和mem_fun_ref之间的确切区别是什么，因为在我看过的所有例子中
，它们的使用方式完全相同？
What is the exact difference between mem_fun and mem_fun_ref, since in all examples I looked at, they are used in exactly the same way?
不同之处在于如何调用成员函数的对象
传递给函子：对于从''mem_fun（）''返回的仿函数a
传递
指向对象的指针。对于从
''mem_fun_ref（）''返回的仿函数，传递对象的引用。虽然
版本都可以折叠成一个函数重载函数
调用运算符，这可能会掩盖某些问题。
-
< mailto：di *********** @ yahoo.com> < http://www.dietmar-kuehl.de/>
< http://www.contendix.com> - 软件开发&咨询
The difference is how the object the member function is called on
is passed to the functor: for a functor returned from ''mem_fun()'' a
pointer to the object is passed. For a functor returned from
''mem_fun_ref()'' a reference to the object is passed. Although both
version could be folded into just one functor overloading the function
call operator, this could obscure certain problems.
--
<mailto:di***********@yahoo.com> <http://www.dietmar-kuehl.de/>
<http://www.contendix.com> - Software Development & Consulting
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