dsinqb.f90 Source File

      subroutine dsinqb(n, x, wsave)
         use fftpack_kind, only: dp => rk
         implicit none
         integer, intent(in) :: n
         real(dp), intent(inout) :: x(*)
         real(dp), intent(in) :: wsave(*)
         integer :: k, kc, ns2
         real(dp) :: xhold
         if (n > 1) then
            ns2 = n/2
            do k = 2, n, 2
               x(k) = -x(k)
            end do
            call dcosqb(n, x, wsave)
            do k = 1, ns2
               kc = n - k
               xhold = x(k)
               x(k) = x(kc + 1)
               x(kc + 1) = xhold
            end do
            return
         end if
         x(1) = 4.0_dp*x(1)
         return
      end subroutine dsinqb