Parameter / argument mismatch in template scenario

Hello all,

I hope the context to my problem shown below is adequate but not
overwhelming. I tried to keep it minimal.

At the line indicated (in comment form) in the source below, the following
error is occurring (VC++ 7.1):
error C2663: 'std::_Tree<_Traits>::find' : 2 overloads have no legal
conversion for 'this' pointer

In Comeau speak:
error: argument of type ... is incompatible with parameter of type ...

If I change part of the line in question to:
((T1 *) &node)

everything works fine (both platforms). However, I may not use the
C++-style casts here - failure still occurs in that case.

Does anybody have nay idea what might be going on?

Thanks,
Dave


// Class declaration:
template <int n>
class repeated_state_checker_t
{
public:
template <typename T1, typename T2>
bool seen_before(
const T1 &node,
const std::set<T1 *, T2> &all_nodes_sorted
) const;
};

// Definition of class full specialization:
template <>
class repeated_state_checker_t<4>
{
public:
template <typename T1, typename T2>
bool seen_before(
const T1 &node,
const std::set<T1 *, T2> &all_nodes_sorted
) const
{
if (all_nodes_sorted.find(&node) != all_nodes_sorted.end()) //
***** ERROR HERE *****
return true;
else
return false;
} // repeated_state_checker_t<4>::seen_before
};

// The class above is a template parameter to my main class; my main class
inherits from the
// template parameter and attempts to invoke the seen_before() method of the
base
// subobject as follows:
REPEATED_STATE_CHECKER::seen_before(
new_node,
all_nodes_sorted
)

// Definition of the type of new_node is shown below. This struct is
embedded in a class template and references
// some of that class template's template parameters.
struct node_t
{
node_t(
const STATE_T &state_p,
int depth_p,
int cost_to_reach_p,
const node_t *parent_p = NULL,
const OP_T &op_p = OP_T()
):
state(state_p),
depth(depth_p),
cost_to_reach(cost_to_reach_p),
parent(parent_p),
op(op_p)
{
}

STATE_T state;
int depth;
int cost_to_reach;
const node_t *parent; // Equals NULL for root node
OP_T op; // Meaningful only if parent !=
NULL
};

// Definition of all_nodes_sorted:
std::set<node_t *, node_sort_t> all_nodes_sorted;

// Definition of node_sort_t:
class node_sort_t
{
public:
bool operator()(const node_t *lhs, const node_t *rhs) const
{
return (lhs->state < rhs->state);
}
};

* "Dave" <better_cs_now@yahoo.com> schriebt:[color=blue]
>
> I hope the context to my problem shown below is adequate but not
> overwhelming. I tried to keep it minimal.[/color]

There's much that's irrelevant, yes. ;-)

[color=blue]
> In Comeau speak:
> error: argument of type ... is incompatible with parameter of type ...
>
> If I change part of the line in question to:
> ((T1 *) &node)
>
> everything works fine (both platforms). However, I may not use the
> C++-style casts here - failure still occurs in that case.[/color]

You may technically use the C++ casts, specifically const_cast.


[color=blue]
> Does anybody have nay idea what might be going on?[/color]

Yes, almost everybody have nay idea what might be going on.

[color=blue]
> // Class declaration:
> template <int n>
> class repeated_state_checker_t
> {
> public:
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2> &all_nodes_sorted[/color]

Make that


std::set<T1 const*, T2>& all_nodes_sorted


or even better use a typedef'ed name.

[color=blue]
> ) const;
> };
>
> // Definition of class full specialization:
> template <>
> class repeated_state_checker_t<4>
> {
> public:
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2> &all_nodes_sorted
> ) const
> {
> if (all_nodes_sorted.find(&node) != all_nodes_sorted.end()) //
> return true;
> else
> return false;[/color]

Make that


return (all_nodes_sorted.find(&node) != all_nodes_sorted.end());


[color=blue]
> } // repeated_state_checker_t<4>::seen_before
> };[/color]

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

* "Dave" <better_cs_now@yahoo.com> schriebt:[color=blue]
>
> I hope the context to my problem shown below is adequate but not
> overwhelming. I tried to keep it minimal.[/color]

There's much that's irrelevant, yes. ;-)

[color=blue]
> In Comeau speak:
> error: argument of type ... is incompatible with parameter of type ...
>
> If I change part of the line in question to:
> ((T1 *) &node)
>
> everything works fine (both platforms). However, I may not use the
> C++-style casts here - failure still occurs in that case.[/color]

You may technically use the C++ casts, specifically const_cast.


[color=blue]
> Does anybody have nay idea what might be going on?[/color]

Yes, almost everybody have nay idea what might be going on.

[color=blue]
> // Class declaration:
> template <int n>
> class repeated_state_checker_t
> {
> public:
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2> &all_nodes_sorted[/color]

Make that


std::set<T1 const*, T2>& all_nodes_sorted


or even better use a typedef'ed name.

[color=blue]
> ) const;
> };
>
> // Definition of class full specialization:
> template <>
> class repeated_state_checker_t<4>
> {
> public:
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2> &all_nodes_sorted
> ) const
> {
> if (all_nodes_sorted.find(&node) != all_nodes_sorted.end()) //
> return true;
> else
> return false;[/color]

Make that


return (all_nodes_sorted.find(&node) != all_nodes_sorted.end());


[color=blue]
> } // repeated_state_checker_t<4>::seen_before
> };[/color]

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Dave wrote:
[color=blue]
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2>
> &all_nodes_sorted
> ) const
> {
> if (all_nodes_sorted.find(&node) !=
> all_nodes_sorted.end()) // ***** ERROR HERE *****
> return true;
> else
> return false;
> }[/color]

The problem is that &node is const T1*
while find expects a non-const pointer.


Martin

--
Quidquid latine dictum sit, altum viditur.

Dave wrote:
[color=blue]
> template <typename T1, typename T2>
> bool seen_before(
> const T1 &node,
> const std::set<T1 *, T2>
> &all_nodes_sorted
> ) const
> {
> if (all_nodes_sorted.find(&node) !=
> all_nodes_sorted.end()) // ***** ERROR HERE *****
> return true;
> else
> return false;
> }[/color]

The problem is that &node is const T1*
while find expects a non-const pointer.


Martin

--
Quidquid latine dictum sit, altum viditur.