function apply( fn, ap :Value ):Value; { apply a function fn to param ap }
   { apply : (Value->Value) -> Value -> Value }
begin if fn^.e^.fparam^.tag = emptycon then { (L().e)ap }
      begin force(ap);
            if ap^.tag = emptyval then apply := eval(fn^.e^.body, fn^.r)
            else error('L().e exp ')
      end
      else apply := eval(fn^.e^.body, bind(fn^.e^.fparam^.id, ap, fn^.r))
end {apply};

{\fB Apply a Function to a Parameter. \fP}