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

From:
"Antoon" <the-dot-Wizard-at-theJuker-dot-org@news1.news.xs4all.nl>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 27 Feb 2008 19:13:54 CST
Message-ID:
<47c53e55$0$14358$e4fe514c@news.xs4all.nl>
<moswald@gmail.com> schreef in bericht
news:2bca9aad-eccb-4bf4-9adf-371ebdac8e01@f47g2000hsd.googlegroups.com...

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
}


A vector actualy has two template parameters: one for the type and one
for an optional allocator.

Perhaps this works better (untested: I don't have access to a modern
compiler
at the moment).

template<template<typename, typename, typename> class container_type,
typename
K, typename V, typename A>
void ContainerDelete(container_type<K, V> &c)
{
     std::for_each(c.begin(), c.end(), AssociativeDelete());
     c.clear();
}

template<template<typename, typename> class container_type, typename T,
typename A>
void ContainerDelete(container_type<T> &c)
{
     std::for_each(c.begin(), c.end(), SequenceDelete());
     c.clear();
}

Antoon

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