declare
Key = ["local" "in" "if" "then" "else" "end"]
Op = ["-" "+" "*" "/" "=" "=="]

fun {Tokenize Xs}
   case Xs of H|T then
      Token =
      if {Member H Key} then
     key({String.toAtom H})
      elseif {Member H Op} then
     op({String.toAtom H})
      elseif {List.length H} > 1 then
     feil({String.toAtom H})
      else case H of F|L then
          if F >= &A andthen F =< &Z then
         id({String.toAtom H})
          elseif F >= &a andthen F =< &z then
         atom({String.toAtom H})
          else
         feil({String.toAtom H})
          end
       end
      end in
      Token|{Tokenize T}
   else nil
   end
end

{Browse {Tokenize ["local" "x" "A" "==" "wdawdew" "(" "end"]}}