Re: What am I missing? (template magic gone wrong)
On 27 Feb, 11:04, mosw...@gmail.com wrote:
From the following code, what am I doing wrong? (I'm using VS2008,
which is better at templates than I am, so I assume I'm missing
something.)
struct SequenceDelete
{
template<typename ptr_type>
void operator()(const ptr_type *p) const
{
delete p;
}
};
struct AssociativeDelete
{
template<typename pair_type>
void operator()(const pair_type &p) const
{
delete p.second;
}
};
template<template<typename, typename> class container_type, typename
K, typename V>
void ContainerDelete(container_type<K, V> &c)
{
std::for_each(c.begin(), c.end(), AssociativeDelete());
c.clear();
}
template<template<typename> class container_type, typename T>
void ContainerDelete(container_type<T> &c)
{
std::for_each(c.begin(), c.end(), SequenceDelete());
c.clear();
}
void Foo()
{
std::map<int, int *> my_map;
for(int i = 0; i != 10; ++i)
my_map[i] = new int();
std::vector<int *> my_vector;
for(int i = 0; i != 10; ++i)
my_vector[i] = new int();
ContainerDelete(my_vector);
ContainerDelete(my_map); // this line fails to compile -- it
treats it as the second template version
}
I think you are making it more complicated than it has to be. The
ContainerDelete function can be implemented like this:
template<typename Container>
void ContainerDelete(Container& c)
{
std::for_each(c.begin(), c.end(), Deleter<Container::value_type>());
}
This will create a Deleter<int*> for the vector, and a
Deleter<std::pair<int,int*> > for the map
The Deleter functor itself can be implemented like this:
template<typename T>
struct Deleter;
template<typename T>
struct Deleter<T*>
{
typedef T* ptr_type;
void operator()(const ptr_type p) const
{
delete p;
}
};
template<typename T1,typename T2>
struct Deleter<std::pair<T1,T2> >
{
typedef std::pair<T1,T2> pair_type;
void operator()(const pair_type& p) const
{
delete p.second;
}
};
Hope this helps.
DP
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