C++ Tutorial/template/template pointer parameter

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template function for reference parameters

/* 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
}

template function to get maximum of two pointers

/* 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
}
42
you
0x22ff58
Nico"

template function with pointer parameter

/* 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";
}
the average value of the integer values is 3
the average value of the characters in "templates" is -5