Вычислить количество цифр среди элементов списка

#include <iostream>
#include <cctype>
using namespace std;
 
struct elem
{
char inf;
elem *link;
};
elem *head, *last, *current;
char ch;
 
//elem* Read(elem *e)
 
void Creating()
{
current = new elem;
cout << "Enter element" << endl;
cin >> current->inf;
current->link = NULL;
if (head == NULL)
 
{
head = current;
last = current;
}
else
{
last->link = current;
last = current;
}
}
 
void Summa(elem *e)
{
int sum = 0;
while (e!=NULL)
{
if (std::isdigit(e->inf))
sum++;
e=e->link;
}
cout << "summa = " << sum << endl;
}
 
void PrintS()
{
cout << "Output list" << endl;
current = head;
while (current != NULL) {
cout << current->inf << endl;
current = current->link;
}
}
 
 
int main()
{
head = NULL;
last = NULL;
do
{
cout<<"Enter command i-input; q-quit" << endl;
cin >> ch;
if (ch == 'i')Creating();
} while (ch != 'q');
PrintS();
cout << endl;
Summa(????);
cout << endl;
system("pause");
return 0;
}

void Kolichestvo(elem *e)
{
int count= 0;
while (e!=NULL)
{
if (std::isdigit(e->inf))
count++;
e=e->link;
}
cout << "Kolichestvo= " << count<< endl;
}