STL排序问题 [英] STL sort question
问题描述
我想用STL排序从std :: vector派生的类：
template< typename T，typename fitParaType，typename fitResType>
class Manipulator {
//我现在不能使用
来访问私人会员//比较？
朋友班比较;
public：
...
void sort（人口< Genome< T，fitParaType>>& pop）;
private：
...
const Functor< fitParaType，fitResType> * _func;
class比较{
public：
比较（）{}
bool operator（）（基因组< T，fitParaType>& arg1，
Genome< T，fitParaType>& arg2）
{
return（_func-> value（arg1.getParams（））
< _func-> value（arg2.getParams（）））;
}
};
};
模板< typename T，typename fitParaType，typename fitResType>
void操纵器< T，适合ParaType，fitResType> :: sort（Population< Genome< T，
fitParaType> >&安培;流行）
{
//人口来自std :: vector
std :: sort（pop.begin（），pop。 end（），Manipulator< T，fitParaType，
fitResType> :: Compare（））;
}
//实例化，所以它编译
模板类操纵器< RealGene< double>，double，double> ;;
我正在尝试比较朋友类的操纵器，所以我可以使用
_func函数。但是，我得到：
/Manipulator.cpp:35：从这里实例化
... / Manipulator.hpp：64：错误：''类操纵器< RealGene< ; double>，double，
double> :: Compare''没有名为''_func'的成员'
如何编写一个Compare类，我可以用来排序吗？有没有比我一直尝试的更好的方式？
谢谢，
Paul Schneider
" Paul Schneider" < PA ******* @ uboot.com>在消息中写道
新闻：c6 ********* @ bird.wu-wien.ac.at ...我想排序一个班级源自STD排序的std :: vector：
模板< typename T，typename fitParaType，typename fitResType>
类操纵器{
//我现在不应该能够访问私人会员
//比较？
朋友类比较;
公开：
...
[snip]
我正在尝试make比较朋友类的Manipulator，所以我可以使用_func函数。但是，我得到了：
/Manipulator.cpp:35：从这里实例化
../Manipulator.hpp:64：错误：''类操纵器< RealGene< double>，double，
double> :: Compare''没有名为''_func'的成员'
如何编写一个可用于排序的Compare类？有没有比我一直尝试的更好的方式？
谢谢，
Paul Schneider
这是一个棘手的领域，我认为最近标准已经改变了关于内部阶级和友谊的标准。但是以下可能更有可能工作
模板< typename T，typename fitParaType，typename fitResType>
类操纵器{
类比较;
朋友类比较;
如果没有前向声明，编译器认为朋友类
比较是指在Manipulator之外声明的类，而不是您稍后声明的内部
类。
john
Paul Schneider写道：我想用STL排序从std :: vector派生的类：
template< typename T， typename fitParaType，typename fitResType>
类操作符{
//我现在不能使用
//比较来访问私有成员吗？
朋友类比较;
我不确定，但我认为那应该是朋友班
Manipulator :: Compare;，以免转发-declare一个类在
名称空间范围内。但这不是你最大的问题。
public：
...
void sort（Population< Genome< T，fitParaType>>& pop）;
私人：
...
const Functor< fitParaType，fitResType> * _func;
类比较{
public：
比较（ ）{}
bool operator（）（Genome< T，fitParaType>& arg1，
Genome< T，fitParaType>& arg2）
{
return（_func-> ; value（arg1.getParams（））
< _func-> value（arg2.getParams（）））;
Manipulator :: Compare对象与Manipulator
对象完全不同。你只能通过Manipulator对象访问Manipulator的非静态成员_func
。
也许Compare对象应该包含自己的_func副本，或者a
对创建Compare对象的Manipulator对象的引用。
我不知道_func的作用。你确定它定义了std :: sort所要求的严格弱的
顺序吗？比较向量的一种常用方法
按字典顺序排列 - 实际上很常见，你可以比较两个
std :: vectors with<或者std :: less。
}
};
};
模板< typename T，typename fitParaType，typename fitResType>
void Manipulator< T，fitParaType，fitResType> :: sort（Population< Genome< T，
fitParaType>>& pop）
//
//群体来源于std :: vector
你可能应该使用委托而不是继承，但是你的电话是
。
std :: sort（ pop.begin（），pop.end（），Manipulator< T，fitParaType，
fitResType> :: Compare（））;
}
//实例化，所以它编译
模板类操纵器< RealGene< double>，double，double> ;;
你确定这是必要的吗？您可能不应该单独编译
模板定义。在
常见问题解答中有一个关于此的条目。
我正在尝试比较朋友类的操纵器，所以我可以使用
_func函数。但是，我得到了：
/Manipulator.cpp:35：从这里实例化
../Manipulator.hpp:64：错误：''类操纵器< RealGene< double>，double，
double> :: Compare''没有名为''_func'的成员'
如何编写一个可用于排序的Compare类？有没有比我尝试过的方式更好的方法？
-
问候，
巴斯特。
John Harrison写道：" Paul Schneider" < PA ******* @ uboot.com>在消息中写道
新闻：c6 ********* @ bird.wu-wien.ac.at ...
我想排序一个班级源自STD排序的std :: vector：
模板< typename T，typename fitParaType，typename fitResType>
类操纵器{
//我现在不应该能够访问私人会员
//比较？
朋友类比较;
公开：
...
[snip]
我正在尝试比较朋友类的操纵器，所以我可以使用_func函数。但是，我得到了：
/Manipulator.cpp:35：从这里实例化
../Manipulator.hpp:64：错误：''类操纵器< RealGene< double>，double，
double> :: Compare''没有名为''_func'的成员'
如何编写一个可用于排序的Compare类？有没有比我尝试过的方式更好的方式？
谢谢，
Paul Schneider
这个是一个棘手的领域，我认为最近有关内部阶级和友谊的标准已经改变了。但是以下可能更有可能工作
模板< typename T，typename fitParaType，typename fitResType>
类操纵器{
类比较;
朋友类比较;
没有前向声明编译器认为朋友类
比较是指在Manipulator之外声明的类，而不是您稍后声明的内部类。 />
john
谢谢，在尝试了你的建议之后，朋友的声明仍然没有工作。 （指针被排除在外吗？）。现在我尝试了以下比较课程：
class比较{
public：
比较（const Functor< fitParaType，fitResType> * func）：_ func（func）{}
bool operator（）（Genome< T，fitParaType>& arg1，
Genome< T，fitParaType>& arg2 ）
{
return（_func-> value（arg1.getParams（））
< _func-> value（arg2。 getParams（）））;
}
private：
const Functor< fitParaType，fitResType> * _func;
$ b $实现sort函数的
：
模板< typename T，typename fitParaType，typename fitResType>
void Manipulator< T，fitParaType，fitResType> :: sort（Population< Genome< T，
fitParaType>>& pop）
{
std :: sort（pop.begin（），pop.end（），this-> Compare（_func））;
}
这只给我一个错误：
... / Manipulator.cpp：32：错误：调用非函数`类
操纵器< RealGene< double>，double，double> ::比较''
如何摆脱这个？
再次感谢，
Paul
I want to sort a class derived from std::vector with STL sort.:
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
// shouldn''t I now be able to access private members with
// Compare?
friend class Compare;
public:
...
void sort(Population<Genome<T, fitParaType> >& pop);
private:
...
const Functor<fitParaType, fitResType>* _func;
class Compare{
public:
Compare(){}
bool operator () (Genome<T, fitParaType>& arg1,
Genome<T, fitParaType>& arg2)
{
return (_func->value(arg1.getParams())
< _func->value(arg2.getParams()));
}
};
};
template<typename T, typename fitParaType, typename fitResType>
void Manipulator<T, fitParaType, fitResType>::sort(Population<Genome<T,
fitParaType> >& pop)
{
// Population is derived from std::vector
std::sort(pop.begin(), pop.end(), Manipulator<T, fitParaType,
fitResType>::Compare() );
}
// instantiation, so it compiles
template class Manipulator<RealGene<double>, double, double>;
I am trying to make Compare a friend class of Manipulator, so I can use
the _func function. However, I am getting:
/Manipulator.cpp:35: instantiated from here
.../Manipulator.hpp:64: error: ''class Manipulator<RealGene<double>, double,
double>::Compare'' has no member named ''_func''
How can I write a Compare class that I can use for sorting? Is there a
better way than the way I have been trying?
Thanks,
Paul Schneider
"Paul Schneider" <pa*******@uboot.com> wrote in message
news:c6*********@bird.wu-wien.ac.at...I want to sort a class derived from std::vector with STL sort.:
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
// shouldn''t I now be able to access private members with
// Compare?
friend class Compare;
public:
... [snip]
I am trying to make Compare a friend class of Manipulator, so I can use
the _func function. However, I am getting:
/Manipulator.cpp:35: instantiated from here
../Manipulator.hpp:64: error: ''class Manipulator<RealGene<double>, double,
double>::Compare'' has no member named ''_func''
How can I write a Compare class that I can use for sorting? Is there a
better way than the way I have been trying?
Thanks,
Paul Schneider
This is a tricky area, and I think the standard has changed recently
concerning inner classes and friendship. However the following is probably
more likely to work
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
class Compare;
friend class Compare;
Without the forward declaration the compiler thinks that friend class
Compare refers to a class declared outside of Manipulator, not the inner
class you declare later.
john
Paul Schneider wrote:I want to sort a class derived from std::vector with STL sort.:
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
// shouldn''t I now be able to access private members with
// Compare?
friend class Compare;
I''m not sure, but I think that should be "friend class
Manipulator::Compare;", so as not to forward-declare a class at
namespace scope. That''s not your biggest problem, though.
public:
...
void sort(Population<Genome<T, fitParaType> >& pop);
private:
...
const Functor<fitParaType, fitResType>* _func;
class Compare{
public:
Compare(){}
bool operator () (Genome<T, fitParaType>& arg1,
Genome<T, fitParaType>& arg2)
{
return (_func->value(arg1.getParams())
< _func->value(arg2.getParams()));
A Manipulator::Compare object is quite different from a Manipulator
object. You can only access the non-static member _func of Manipulator
through a Manipulator object.
Perhaps the Compare object should contain its own copy of _func, or a
reference to the Manipulator object which created the Compare object.
I don''t know what _func does. Are you sure it defines a strict weak
ordering, as required by std::sort? A common way to compare vectors
is lexicographically -- so common, in fact, that you can compare two
std::vectors with < or std::less.
}
};
};
template<typename T, typename fitParaType, typename fitResType>
void Manipulator<T, fitParaType, fitResType>::sort(Population<Genome<T,
fitParaType> >& pop)
{
// Population is derived from std::vector
You should probably using delegation rather than inheritance, but it''s
your call.
std::sort(pop.begin(), pop.end(), Manipulator<T, fitParaType,
fitResType>::Compare() );
}
// instantiation, so it compiles
template class Manipulator<RealGene<double>, double, double>;
Are you sure that''s necessary? You should probably not be compiling the
template definitions separately. There is an entry about this in the
FAQ.
I am trying to make Compare a friend class of Manipulator, so I can use
the _func function. However, I am getting:
/Manipulator.cpp:35: instantiated from here
../Manipulator.hpp:64: error: ''class Manipulator<RealGene<double>, double,
double>::Compare'' has no member named ''_func''
How can I write a Compare class that I can use for sorting? Is there a
better way than the way I have been trying?
--
Regards,
Buster.
John Harrison wrote:"Paul Schneider" <pa*******@uboot.com> wrote in message
news:c6*********@bird.wu-wien.ac.at...I want to sort a class derived from std::vector with STL sort.:
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
// shouldn''t I now be able to access private members with
// Compare?
friend class Compare;
public:
...
[snip]I am trying to make Compare a friend class of Manipulator, so I can use
the _func function. However, I am getting:
/Manipulator.cpp:35: instantiated from here
../Manipulator.hpp:64: error: ''class Manipulator<RealGene<double>, double,
double>::Compare'' has no member named ''_func''
How can I write a Compare class that I can use for sorting? Is there a
better way than the way I have been trying?
Thanks,
Paul Schneider
This is a tricky area, and I think the standard has changed recently
concerning inner classes and friendship. However the following is probably
more likely to work
template<typename T, typename fitParaType, typename fitResType>
class Manipulator{
class Compare;
friend class Compare;
Without the forward declaration the compiler thinks that friend class
Compare refers to a class declared outside of Manipulator, not the inner
class you declare later.
john
Thanks, after trying your suggestion the friend statement still doesn''t
work. (Are pointers excluded?). Now I tried the following Compare class:
class Compare{
public:
Compare(const Functor<fitParaType, fitResType>* func) : _func(func){}
bool operator () (Genome<T, fitParaType>& arg1,
Genome<T, fitParaType>& arg2)
{
return (_func->value(arg1.getParams())
< _func->value(arg2.getParams()));
}
private:
const Functor<fitParaType, fitResType>* _func;
};
with implementation of the sort function:
template<typename T, typename fitParaType, typename fitResType>
void Manipulator<T, fitParaType, fitResType>::sort(Population<Genome<T,
fitParaType> >& pop)
{
std::sort(pop.begin(), pop.end(), this->Compare(_func) );
}
This gives me only one error:
.../Manipulator.cpp:32: error: call to non-function `class
Manipulator<RealGene<double>, double, double>::Compare''
How can I get rid of this?
Thanks again,
Paul
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