constructor Function

  function constructor(domain, resolution, thickness, velocity, &
                       viscosity_law, lambda, chi) result(this)
    !* Author: Christopher MacMackin
    !  Date: April 2016
    !
    ! Creates a new [[ice_sheet]] object with initial conditions provided
    ! by the arguments. At present only a 1D model is supported. If
    ! information is provided for higher dimensions then it will be ignored.
    !
    real(r8), dimension(:,:), intent(in)            :: domain
      !! An array containing the upper and lower limits of the domain for
      !! the ice sheet. The first index represents the dimension for which
      !! the boundaries apply. If the second index is 1 then it corresponds
      !! to the lower bound. If the second index is 2 then it corresponds to
      !! the upper bound.
    integer, dimension(:), intent(in)               :: resolution
      !! The number of data points in each dimension
    procedure(thickness_func)                       :: thickness
      !! A function which calculates the initial value of the thickness of 
      !! the ice sheet at a given location.
    procedure(velocity_func)                        :: velocity
      !! A function which calculates the initial value of the velocity 
      !! (vector) of the ice at a given location in an ice sheet.
    class(abstract_viscosity), intent(in), optional :: viscosity_law
      !! An object which calculates the viscosity of the ice.
    real(r8), intent(in), optional                  :: lambda
      !! The dimensionless ratio 
      !! $\lambda \equiv \frac{\rho_0m_0x_0}{\rho_iH-0u_0}$
    real(r8), intent(in), optional                  :: chi
      !! The dimensionless ratio
      !! $\chi \equiv \frac{\rho_igh_0x_x}{2\eta_0u_0}$
    type(ice_sheet)                                 :: this
      !! An ice sheet object with its domain and initial conditions set
      !! according to the arguments of the constructor function.
  end function constructor