Re: What am I missing? (template magic gone wrong)

From:
gnuyuva <gnuyuva@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 28 Feb 2008 05:13:20 CST
Message-ID:
<651c4648-4c10-4e66-a823-313665b00c54@i29g2000prf.googlegroups.com>
On Feb 27, 3:04 pm, 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();

This should be my_vector.push_back( new int() );

The declarations of vector and map are:

template <typename VaTy, typename AlTy = std::allocator<VaTy> >
class vector;

template <typename KeyTy, typename VaTy, typename SortTy = ... ,
typename AlTy = ... >
class map;

    ContainerDelete(my_vector);

For me this line failed to compile. The compiler said: ambiguity
between two functions.
And it is because of default value supplied to allocator type (2nd
arg).

    ContainerDelete(my_map); // this line fails to compile -- it
treats it as the second template version

}


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