cyl_to_cart Subroutine

  subroutine cyl_to_cart(Xcyl,X)
    !! @note  Subroutine that converts the position of simulated particles
    !! from cylindrical \((R,\phi,Z)\) to Cartesian \((x,y,z)\ coordinates.
    !! @endnote
    !! Here, the coordinate transformation is:
    !!
    !! $$x=R\cos(\phi),$$
    !! $$y=R\sin(\phi),,$$
    !! $$Z = z.$$
    implicit none
    REAL(rp), DIMENSION(:,:), ALLOCATABLE, INTENT(INOUT):: X
    !! Particles' position in Cartesian coordinates. X(1,:) = \(x\), X(2,:)
    !! = \(y\), X(3,:) = \(z\)
    REAL(rp), DIMENSION(:,:), ALLOCATABLE, INTENT(IN)   :: Xcyl
    !! Particles' position in cylindrical coordinates. Xcyl(1,:) = \(R\),
    !! Xcyl(2,:) = \(\phi\), Xcyl(3,:) = \(Z\)
    INTEGER                                                :: pp
    !! Iterator.
    INTEGER                                                :: ss
    !! Iterator.
    
    if (size(Xcyl,1).eq.1) then
       ss = size(Xcyl,1)
    else
       if (Xcyl(2,1).eq.0) then
          ss=1_idef
       else
          ss = size(Xcyl,1)
       end if
    endif
    

    !$OMP PARALLEL DO FIRSTPRIVATE(ss) PRIVATE(pp) SHARED(X,Xcyl)
    do pp=1_idef,ss
       X(pp,1) = Xcyl(pp,1)*cos(Xcyl(pp,2))
       X(pp,2) = Xcyl(pp,1)*sin(Xcyl(pp,2))
       X(pp,3) = Xcyl(pp,3)
    end do
    !$OMP END PARALLEL DO
  end subroutine cyl_to_cart