text: #---------- PRODUCING EQUATIONS OF SCALAR FIELD ----------#
  
  from objects.fields.scalarfield import ScalarField
  from sympy import latex
  
  
  def cd_scalarfield_ep(coord_sys, scalar_field, index_symbol):
      """
      Producing equations of covariant derivative for a scalar field
  
      Args:
          coord_sys [list]: The coordinate system given as a list (e.g., [t,x,y,z])
          scalar_field [sympy.symbol]: The scalar field, provided by the user
          index_symbol [sympy.symbol]: The index of the coordinate system given as a symbol (e.g., t, r, theta or phi)
      """
      sf = ScalarField(coord_sys, scalar_field)
      index_int = coord_sys.index(index_symbol)
      cd_component = latex(index_symbol)
      cd_eqn = latex(sf.cal_covariant_derivative(index_int))
      return '$$\\nabla_{{{0}}}\phi = {1}$$'.format(cd_component, cd_eqn)
  
  
  def ld_scalarfield_ep(coord_sys, scalar_field, X):
      """
      Producing equations of lie derivative of a scalar field with respect to a vector field, X
  
      Args:
          coord_sys [list]: The coordinate system given as a list (e.g., [t,x,y,z])
          scalar_field [sympy.symbol]: The scalar field, provided by the user
          X [list]: Given vector field that the lie derivative is taken w.r.t
      """
      sf = ScalarField(coord_sys, scalar_field)
      ld_eqn = latex(sf.cal_lie_derivative(X))
      return '$$\mathcal{{L}}_X\phi = {0}$$'.format(ld_eqn)
  