Declaritive Programming

local X1 in
     local X2 in
          X1 = 1
          Ans=X1+X2
     end
end


How do you tell the difference between bound and free occurrences?  Also how do you tell between bound stored variables and undetermined variables?

If there's a var/local associated with the name in one of them enclosing scopes, then the variable is bound to that scope. Otherwise, it usually goes in the mythical "global environment".