Chapter 17
Templates
Generic Algorithms
Algorithms in which the actions or steps are
defined, but the data types of the items
being manipulated are not.
Examples Of Generic Algorithm
• Swap the values of two variables of the same
data types
• Find the index of the smallest value in an
array.
• Pair up 2 values
• Linked list
Overloading functions for Generic
Algorithms
void swap (char& v1, char& v2)
{
char temp = v1;
v1 = v2;
v2 = v3;
}
void swap (int& v1, int& v2)
{
int temp = v1;
v1 = v2;
v2 = v3;
}
void double (double & v1, double & v2)
{
double temp = v1;
v1 = v2;
v2 = v3;
}
void swap (CAny& v1, CAny& v2)
{
CAny temp = v1;
v1 = v2;
v2 = v3;
}
Template for Functions
template <class T>
void swap (T& v1, T& v2)
{
T temp = v1;
v1 = v2;
v2 = temp;
}
int main ()
{
int i1=1, i2=2;
swap (i1, i2);
char c1=‘a’, c2=‘A’;
swap (c1, c2);
}
Template Function Notes
• The words template <class T> tell the compiler
this is a template for a generic data type T and
that T is the parametized type which can be
replaced by a defined data type.
• T must have all of the operations used in the
template function.
int a[5], b[5];
… // Some code to fill up arrays
swap (a, b); // NO! There is no assignment operator for arrays
Class Template
//Class template for a pair of values of type T
template <class T>
class Pair
{
public:
Pair();
Pair(T f, T s);
void setElement (int pos, T val);
T getElement (int pos);
private:
T first;
T second;
};
Class Template (cont.)
template <class T>
Pair<T>::Pair() {}
template <class T>
Pair<T>::Pair(T f, T s) {
first = f;
second = s;
}
template <class T>
void Pair<T>::setElement (int pos, T val) {
if (pos == 1)
first = val;
else
second = val;
}
template <class T>
T Pair<T>::getElement (int pos) {
if (pos == 1)
return first;
else
return second;
}
void main ()
{
Pair<int> scores;
Pair<char>seats(‘A’, ‘B’);
score.setElement(1, 3);
score.setElement(2, 5);
char mySeat;
mySeat=seats.getElement(1);
}
Class Template Notes
• The words template <class T> tell the compiler this is
a template for a generic data type T and that T is the
parametized type which can be replaced by a defined
data type.
• T is used as a type in all function definitions or
parameters of the class template.
• You can use typedef to improve readability.
typedef Pairs<int> PairsOfInt;
then declare PairsOfInt score;
• Type T is specialized by giving a type argument to the
class name in place of the T.