C++ for Scientists - Technische Universität Dresden

96 CHAPTER 4. GENERIC PROGRAMMING
vector( const vector& that )
: my size(that.my size), data( new T[my size] )
{
for (int i= 0; i < my size; ++i)
data[i]= that.data[i];
}
∼vector() { if (data) delete [] data ; }
vector& operator=( const vector& that )
{
check size(that.my size);
for (int i= 0; i < my size; ++i)
data[i]= that.data[i];
}
int size() const { return my size ; }
const T& operator[]( int i ) const
{
check index(i);
return data[i];
}
T& operator[]( int i )
{
check index(i);
return data[i] ;
}
vector operator+( const vector& that ) const
{
check size(that.my size);
vector sum(my size);
for (int i= 0; i < my size; ++i)
sum[i]= data[i] + that[i];
return sum ;
}
private:
int my size ;
T∗ data ;
};
Listing 4.1: Template vector class
The template class is not essentially different to a non-template class. There is only the extra
parameter T as placeholder for the type that the class is used with.
We have member variables like my size and member functions size() that are not affected by
the template parameter. Other functions like the access operator or the first constructor are
parametrized. However the difference is minimal, whereever we had double (or another type)
before we put now the type parameter T, e.g. for return types or within new. Likewise our
member variables and constants can be parametrized by T as for data. Even program parts
that use generic functions or data can be often implemented without explicitly stating the