C++ for Scientists - Technische Universität Dresden

4.11. EXERCISES 131
double operator() ( double x ) const {
return std::exp( 3.0 ∗ x ) ;
}
} ;
• f = sin(x) if x < 1 and f = cos(x) if x ≥ 1 for x ∈ [0, 4].
• Can we use trapezoid( std::sin, 0.0, 2.0 ); ?
As a second exercise, develop a functor for computing the finite difference. Then integrate the
finite difference to verify that you get the function value back.
4.11.11 STL and functor
Write a generic function that copies the values of a container to another container after transformation
using a functor:
struct double functor {
int operator() ( int v ) const {
if (v my input vec ; ...
std::vector< int > my output vec ;
transform( my input vec.begin(), my input vec.end(), my output vec.begin(), double functor() ) ;
Write code for the function transform and test it.