class Pos private(val prog: String, val offs: Int, val line: Int, val col: Int) {
  def this(prog: String) = this(prog, 0, 1, 1)

  def ch = if (offs == prog.length) -1 else prog(offs)

  def inc = ch match {
    case '\n' => new Pos(prog, offs+1, line+1, 1)
    case -1   => this
    case _    => new Pos(prog, offs+1, line, col+1)
  }

  override def toString = "(" + line + ", " + col + ")"
}

object DomainTags extends Enumeration {
  type Tag = Value
  val WHITESPACE, IDENT, NUMBER, OPER, ERROR, END_OF_PROGRAM = Value
}
import DomainTags._

class Scanner {
  def scan(start: Pos, errs: List[String]): (Tag, Pos, List[String]) =
  {   
    (ERROR, start.inc, ("unexpected symbol " + start)::errs)
    }
}

class Token(val start: Pos, scanner: Scanner, errs: List[String]) {
  val (tag, follow, errsl) = start.ch match {
    case -1 => (END_OF_PROGRAM, start, errs)
    case _  => scanner.scan(start, errs)
  }

  def image = start.prog.substring(start.offs, follow.offs)

  def next = new Token(follow, scanner, errsl)

  def listacc = errs
}

trait Oper extends Scanner {
  private def findoper(pos: Pos, fstate: Boolean, sstate: Boolean, tstate: Boolean): (Pos, Boolean, Boolean, Boolean) = pos.ch match {
    case a if (( a == '<' ) && !fstate && !sstate && !tstate ) => 
    findoper(pos.inc, true, false, false)
    case a if ((a == '=') && fstate && !sstate && !tstate ) => 
    (pos.inc, true, true, false)
    case a if ((a == '=') && !fstate && !sstate && !tstate ) => 
    findoper(pos.inc, false, true, false)
    case a if ((a == '=') && !fstate && sstate && !tstate ) => 
    (pos.inc, false, true, true)
    case a if ((a != '=') && !fstate && sstate && !tstate ) => 
    (pos, false, true, true)
    case _    => 
    (pos, false, false, false)
  }

  override def scan(start: Pos, errs: List[String]) = {
    val (follow, flag1, flag2, flag3) = findoper(start, false, false, false)
    if ((start != follow) && ((flag1 && flag2) | (flag2) | (flag2 && flag3)) ) (OPER, follow, errs)
    else super.scan(start, errs)   
  } 
}

trait Number extends Scanner {
  private def findnumber(pos: Pos, fstate: Boolean, sstate: Boolean, tstate: Boolean, errstate: Boolean): (Pos, Boolean, Boolean, Boolean, Boolean) = pos.ch match {
    case a if ( (a == '<') && (!tstate) ) => 
    findnumber(pos.inc, true, sstate, tstate, false)
    case a if ( (a >= '0') && (a <= '9') ) => 
    findnumber(pos.inc, fstate, true, tstate, errstate)
    case a if ( (a == '>') && (fstate) ) => 
    (pos.inc, fstate, sstate, true, errstate)
    case a if ( ( ( (a >= 'a') && (a <= 'z') ) || (a == ' ')) && (fstate) && (!tstate) && (a != '=') ) =>
    findnumber(pos.inc, fstate, false, tstate, true)
    case _    => 
    (pos, fstate, sstate, tstate, fstate)
  }

  override def scan(start: Pos, errs: List[String]) = {
    val (follow, flag1, flag2, flag3, flag4) = findnumber(start, false, false, false, false)

    if ((start != follow)&& flag1 && flag2  && flag3 && (!flag2 || !flag4)) (NUMBER, follow, errs)
    else if ((start != follow) && flag1 &&  flag3 && (!flag2 || flag4)) {
      //println("error in digit part")
      //(ERROR, follow)
      (NUMBER, follow, ("error in digit part" + follow)::errs)

    }
     else super.scan(start, errs)   
  } 
}

trait Ident extends Scanner {
  private def findident(pos: Pos, fstate: Boolean, sstate: Boolean): (Pos, Boolean, Boolean) = pos.ch match {
    case a if ((a >= 'a') && (a <= 'z'))  => 
    findident(pos.inc, true, false)
    case a if ((a >= '0') && (a <= '9'))  => 
    findident(pos.inc, fstate, true)
    case _    => 
    (pos, fstate, sstate)
  }

  override def scan(start: Pos, errs: List[String]) = {
    val (follow, flag1, flag2) = findident(start, false, false)

    if ((start != follow) && flag2) (IDENT, follow, errs)
    else if ((start != follow) && flag1 && !flag2) {
      //println("digit expected")
      //(ERROR, follow)
      (IDENT, follow, ("digit expected" + follow)::errs)
    } else super.scan(start, errs)   
  } 
}

trait Whitespaces extends Scanner {
  private def missWhitespace(pos: Pos): Pos = pos.ch match {
    case ' '  => missWhitespace(pos.inc)
    case '\t' => missWhitespace(pos.inc)
    case '\n' => missWhitespace(pos.inc)
    case _    => pos
  }

  override def scan(start: Pos, errs: List[String]) = {
    val follow = missWhitespace(start)
    if (start != follow) (WHITESPACE, follow, errs)
    else super.scan(start, errs)
  }
}

val str = "<1 2>= q1q 1q1 \n w1w1 <2><==== <2q> 11 &"
println(str)
var t = new Token(
  new Pos(str),
  new Scanner with Oper  with Number with Ident with Whitespaces,
  Nil
)

while (t.tag != END_OF_PROGRAM) {
  if (t.tag != ERROR && t.tag != WHITESPACE) println(t.tag.toString + " " + t.start + "-" + t.follow + ": " + t.image)
  t = t.next
}

def printerrs(errs: List[String]): List[String] = errs match {
  case Nil => Nil
  case x::l => {println("err:" + x)
                printerrs(l)} 
}

printerrs(t.listacc)