C++ for Scientists - Technische Universität Dresden

2.9. ARRAYS 49
• : Complex numbers
• , , , , ...: STL, see Section 4.9
Inline keyword
Instead of creating a library as described at the beginning of this section, we can also store the
implementation in the header file. We then have to add the keyword inline for two reasons. The
code will not be stored in a library but inlined in the calling functions: this may lead to more
efficient code when the functions are small. If we do not use the inline keyword, we may end
up with multiple defined functions, since the compiler will create the methods in every source
file they are used.
Consider for example the following header file sqr.hpp:
#ifndef athens sqr hpp
#define athens sqr hpp
inline double sqr(double a)
{ return a∗a;}
#endif
2.9 Arrays
C based programming languages are not very good at working with arrays. In this section, we
discuss the language concepts for arrays. In Section 4.9, we will present more practical software
for arrays and other complicated mass data structures.
An array is created as follow
int x[10];
The variable x is a constant size array. It allows for fast creation (it is typically stored on the
stack).
Arrays are accessed by square brackets: x[i] is a reference to the ith element. The first element
is x[0], the last one is x[9]. Arrays can be initialized at the definition
float v[]= {1.0, 2.0, 3.0}, w[]= {7.0, 8.0, 9.0};
In this case, the array size is deduced.
Operations on arrays are typically performed in loops, e.g. to compute x = v − 3w as vector
operation is realized by
float x[3];
for (int i= 0; i < 3; i++)
x[i]= v[i] − 3.0 ∗ w[i];
One can also define arrays of higher dimension