type token =
  | TIntKw
  | TBoolKw
  | TVoidKw
  | TStructKw
  | TIf
  | TElse
  | TFor
  | TEach
  | TForEach
  | TIn
  | TReturn
  | TTrue
  | TFalse
  | TFn
  | TLet
  | TMut
  | TIdent of string
  | TIntLit of int
  | TLParen
  | TRParen
  | TLBrace
  | TRBrace
  | TLBracket
  | TRBracket
  | TSemicolon
  | TComma
  | TDot
  | TAssign
  | TPlus
  | TMinus
  | TStar
  | TSlash
  | TPercent
  | TAndAnd
  | TOrOr
  | TBang
  | TEqEq
  | TNe
  | TLt
  | TLe
  | TGt
  | TGe
  | TEOF
  | TArrow
  | TColon
  | THash

exception Lex_error of string

val lex : string -> token list