Mega Code Archive
Template class Demo
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/* 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>
class AccumulationTraits;
template<>
class AccumulationTraits<char> {
public:
typedef int AccT;
};
template<>
class AccumulationTraits<short> {
public:
typedef int AccT;
};
template<>
class AccumulationTraits<int> {
public:
typedef long AccT;
};
template<>
class AccumulationTraits<unsigned int> {
public:
typedef unsigned long AccT;
};
template<>
class AccumulationTraits<float> {
public:
typedef double AccT;
};
template <typename T>
inline
typename AccumulationTraits<T>::AccT accum (T const* beg,
T const* end)
{
// return type is traits of the element type
typedef typename AccumulationTraits<T>::AccT AccT;
AccT total = AccT(); // assume AccT() 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 108
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