This class attempts to compute a Fourier integral of the function f over the semiinfinite interval [a,+Infinity).

                        +Infinity                           +Infinity
             I = Integral dx f(x) sin(wt)   or   I = Integral dx f(x) cos(wx)
                        a                                   a

The parameter w and choice of sin or cos is taken from the table wf (the length L can take any value, since it is overridden by this function to a value appropriate for the fourier integration). The integral is computed using the QAWO algorithm over each of the subintervals,

             C1 = [a, a + c]
             C2 = [a + c, a + 2c]
             . . . = . . .
             Ck = [a + (k - 1)c, a + kc]

where c = (2floor(|w|) + 1)Pi/|w|. The width c is chosen to cover an odd number of periods so that the contributions from the intervals alternate in sign and are monotonically decreasing when f is positive and monotonically decreasing. The sum of this sequence of contributions is accelerated using the epsilon-algorithm.

Ref.: Gnu Scientific library reference manual ()