Write a lexical analyzer which uses above types to generate sequence of tokens from the input string. You will tokenize strings composed of integer numbers and arithmetic operations. Let's define...

Write a lexical analyzer which uses above types to generate sequence of tokens from the input string. You will tokenize strings composed of integer numbers and arithmetic operations. Let's define these tokens.

//

// RUN THIS CELL BEFORE CONTINUE

//

type TOKEN =

| INT of int // integer number

| ADD_OP   // addition operation

| SUB_OP   // subtraction operation

| MUL_OP   // multiplication operation

| UNKNOWN  // uknown symbol

| EOF      // end of input

// helper functions

let charsToInt (cs:char list) :int =

List.fold (fun a c -> a + string c) "" cs |> int