The main documentation of the Valid_State_Monomial Procedure contains additional explanation of this code listing.
function Valid_State_Monomial (Monomial) result(Valid)
! Input variables.
! Variable to be checked.
type(Monomial_type), intent(in) :: Monomial
! Output variables.
type(logical) :: Valid ! Logical state.
!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
! Start out true.
Valid = .true.
! Check for association of pointered internals.
Valid = Valid .and. ASSOCIATED(Monomial%Mesh)
Valid = Valid .and. ASSOCIATED(Monomial%Structure)
if (.not.Valid) return
! Check for validity of internals.
Valid = Valid .and. Initialized(Monomial)
Valid = Valid .and. Valid_State(Monomial%Coefficient)
Valid = Valid .and. Valid_State(Monomial%Exponent)
Valid = Valid .and. Valid_State(Monomial%Locus)
Valid = Valid .and. Valid_State(Monomial%Name)
Valid = Valid .and. Valid_State(Monomial%Phi)
if (.not.Valid) return
! Checks on the validity of Monomial -- none.
! Valid = Valid .and. test1
return
end function Valid_State_Monomial