C++ Tutorial/template/template pointer parameter
template function for reference parameters
<source lang="cpp">/* The following code example is taken from the book
* "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <string>
// note: reference parameters template <typename T> inline T const& max (T const& a, T const& b) {
return a < b ? b : a;
} int main() {
std::string s;
::max("apple","peach"); // OK: same type
//::max("apple","tomato"); // ERROR: different types
//::max("apple",s); // ERROR: different types
}</source>
template function to get maximum of two pointers
<source lang="cpp">/* The following code example is taken from the book
* "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
- include <cstring>
- include <string>
// maximum of two values of any type template <typename T> inline T const& max (T const& a, T const& b) {
return a < b ? b : a;
} // maximum of two pointers template <typename T> inline T* const& max (T* const& a, T* const& b) {
return *a < *b ? b : a;
} // maximum of two C-strings inline char const* const& max (char const* const& a,
char const* const& b)
{
return std::strcmp(a,b) < 0 ? b : a;
} int main () {
int a=7; int b=42; std::cout<<"\n\n" << ::max(a,b); // max() for two values of type int std::string s="hey"; std::string t="you"; std::cout<<"\n\n" << ::max(s,t); // max() for two values of type std::string int* p1 = &b; int* p2 = &a; std::cout<<"\n\n" << ::max(p1,p2); // max() for two pointers char const* s1 = "David"; char const* s2 = "Nico"; std::cout<<"\n\n" << ::max(s1,s2); // max() for two C-strings
}</source>
42 you 0x22ff58 Nico"
template function with pointer parameter
<source lang="cpp">/* The following code example is taken from the book
* "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
template <typename T> inline T accum (T const* beg, T const* end) {
T total = T(); // assume T() actually creates a zero value
while (beg != end) {
total += *beg;
++beg;
}
return total;
}
int main() {
// create array of 5 integer values
int num[] = { 1, 2, 3, 4, 5 };
// print average value
std::cout << "the average value of the integer values is "
<< accum(&num[0], &num[5]) / 5
<< "\n";
// create array of character values
char name[] = "templates";
int length = sizeof(name)-1;
// (try to) print average character value
std::cout << "the average value of the characters in \""
<< name << "\" is "
<< accum(&name[0], &name[length]) / length
<< "\n";
}</source>
the average value of the integer values is 3 the average value of the characters in "templates" is -5
