Thread: ambiguous call to overloaded function

This code is an example from a C++ book, using overloaded template function. One template is for normal arrays and another one is for arrays to pointers. According to the book the compiler will find out which template to use, but I get two fault codes:

error C2667: 'ShowArray' : none of 2 overload have a best conversion
error C2668: 'ShowArray' : ambiguous call to overloaded function

Code:

#include <iostream>
using namespace std;

template <typename T>				//template A
void	ShowArray(T arr[], int n);

template <typename T>				//template B
void	ShowArray(T *arr[], int n);

struct	debts {
	char	name[50];
	double	amount;
};

int		main(void)
{
	int		things[6] = {13, 31, 103, 301, 310, 130};
	debts mr_E[3] = {
		{"Ima Wolfe", 2400.0},
		{"Ura Foxe", 1300.0},
		{"Iby Stout", 1800.0}
	};
	double	*pd[3];

	for (int i = 0; i < 3; ++i)
		pd[i] = &mr_E[i].amount;

	cout << "Showing Mr. E's things:\n";
	ShowArray(things, 6);
	cout << "Showing Mr. E's debts:\n";
	ShowArray(pd, 3);
	return 0;
}

template <typename T>
void	ShowArray(T arr[], int n)
{
	cout << "template A\n";
	for (int i = 0; i < n; ++i)
		cout << arr[i] << ' ';
	cout << endl;
}

template <typename T>
void	ShowArray(T *arr[], int n)
{
	cout << "template B\n";
	for (int i = 0; i < n; ++i)
		cout << *arr[i] << ' ';
	cout << endl;
}

I'm using MSVC 6.
Why isn't this working?
Please, someone who can explain this?

Ok, it works with the template parameter, but I still don't get it.

I don't use template parameter when calling the function with int data ( ShowArray(things, 6); ) and this works anyway.

According to the book the compiler will find out which instance to make from the type of data used in the arguments. The ShowArray(pd, 3); call will fit both templates but template B is more specialized so the compiler will choose it, it says.

Why will the <double> parameter make the compiler to choose template B and not A? This confuses me.