20 case class RECD(x: String, r: Rexp) extends Rexp

    23 case class RECD(x: String, r: Rexp) extends Rexp {

    24   override def toString = "[" + r.toString +"]"

    25 }

    26 

    27 

    28 abstract class Val

    29 case object Empty extends Val

    30 case class Chr(c: Char) extends Val

    31 case class Sequ(v1: Val, v2: Val) extends Val

    32 case class Left(v: Val) extends Val

    33 case class Right(v: Val) extends Val

    34 case class Stars(vs: List[Val]) extends Val

    35    

    36 // nullable function: tests whether the regular 

    37 // expression can recognise the empty string

    38 def nullable (r: Rexp) : Boolean = r match {

    39   case ZERO => false

    40   case ONE => true

    41   case CHAR(_) => false

    42   case ANYCHAR => false

    43   case ALT(r1, r2) => nullable(r1) || nullable(r2)

    44   case SEQ(r1, r2) => nullable(r1) && nullable(r2)

    45   case STAR(_) => true

    46   case RECD(_, r1) => nullable(r1)

    47 }

    48 

    49 // derivative of a regular expression w.r.t. a character

    50 def der (c: Char, r: Rexp) : Rexp = r match {

    51   case ZERO => ZERO

    52   case ONE => ZERO

    53   case CHAR(d) => if (c == d) ONE else ZERO

    54   case ANYCHAR => ONE

    55   case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))

    56   case SEQ(r1, r2) => 

    57     if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))

    58     else SEQ(der(c, r1), r2)

    59   case STAR(r) => SEQ(der(c, r), STAR(r))

    60   case RECD(_, r1) => der(c, r1)

    61 }

    62 

    63 // derivative w.r.t. a string (iterates der)

    64 def ders (s: List[Char], r: Rexp) : Rexp = s match {

    65   case Nil => r

    66   case c::s => ders(s, der(c, r))

    67 }

    68 

    69 // extracts a string from value

    70 def flatten(v: Val) : String = v match {

    71   case Empty => ""

    72   case Chr(c) => c.toString

    73   case Left(v) => flatten(v)

    74   case Right(v) => flatten(v)

    75   case Sequ(v1, v2) => flatten(v1) + flatten(v2)

    76   case Stars(vs) => vs.map(flatten).mkString

    77 }

    78 

    79 // extracts an environment from a value

    80 def env(v: Val, r: Rexp) : List[(String, String)] = (v, r) match {

    81   case (Empty, ONE) => Nil

    82   case (Chr(c), CHAR(_)) => Nil

    83   case (Chr(c), ANYCHAR) => Nil

    84   case (Left(v), ALT(r1, r2)) => env(v, r1)

    85   case (Right(v), ALT(r1, r2)) => env(v, r2)

    86   case (Sequ(v1, v2), SEQ(r1, r2)) => env(v1, r1) ::: env(v2, r2)

    87   case (Stars(vs), STAR(r)) => vs.flatMap(env(_, r))

    88   case (v, RECD(x, r)) => (x, flatten(v))::env(v, r)

    89 }

    90 

    91 // extracts indices for the underlying strings

    92 def env2(v: Val, r: Rexp, n: Int) : (List[(Int, Int)], Int) = (v, r) match {

    93   case (Empty, ONE) => (Nil, n)

    94   case (Chr(c), CHAR(_)) => (Nil, n + 1)

    95   case (Chr(c), ANYCHAR) => (Nil, n + 1)

    96   case (Left(v), ALT(r1, r2)) => env2(v, r1, n)

    97   case (Right(v), ALT(r1, r2)) => env2(v, r2, n)

    98   case (Sequ(v1, v2), SEQ(r1, r2)) => {

    99    val (e1, n1) = env2(v1, r1, n) 

   100    val (e2, n2) = env2(v2, r2, n1)

   101    (e1 ::: e2, n2)

   102   }

   103   case (Stars(Nil), STAR(r)) => (Nil, n)

   104   case (Stars(v :: vs), STAR(r)) => {

   105    val (e1, n1) = env2(v, r, n) 

   106    val (e2, n2) = env2(Stars(vs), STAR(r), n1)

   107    (e1 ::: e2, n2)

   108   }

   109   case (v, RECD(x, r)) => {

   110     val (e1, n1) = env2(v, r, n)

   111     ((n, n + flatten(v).length) :: e1, n1)

   112   }

   113 }

   114 

   115 // injection part

   116 def mkeps(r: Rexp) : Val = r match {

   117   case ONE => Empty

   118   case ALT(r1, r2) => 

   119     if (nullable(r1)) Left(mkeps(r1)) else Right(mkeps(r2))

   120   case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))

   121   case STAR(r) => Stars(Nil)

   122   case RECD(x, r) => mkeps(r)

   123 }

   124 

   125 def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {

   126   case (STAR(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)

   127   case (SEQ(r1, r2), Sequ(v1, v2)) => Sequ(inj(r1, c, v1), v2)

   128   case (SEQ(r1, r2), Left(Sequ(v1, v2))) => Sequ(inj(r1, c, v1), v2)

   129   case (SEQ(r1, r2), Right(v2)) => Sequ(mkeps(r1), inj(r2, c, v2))

   130   case (ALT(r1, r2), Left(v1)) => Left(inj(r1, c, v1))

   131   case (ALT(r1, r2), Right(v2)) => Right(inj(r2, c, v2))

   132   case (CHAR(d), Empty) => Chr(c) 

   133   case (ANYCHAR, Empty) => Chr(c) 

   134   case (RECD(x, r1), _) => inj(r1, c, v)

   135 }

   136 

   137 

   138 // main lexing function (produces a value)

   139 def lex(r: Rexp, s: List[Char]) : Val = s match {

   140   case Nil => if (nullable(r)) mkeps(r) else throw new Exception("Not matched")

   141   case c::cs => inj(r, c, lex(der(c, r), cs))

   142 }

   143 

   144 def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)

   145 

   146 

   147 

   148 // Regular expression parser

    42       if (more() && peek() != ')' && peek() != '|') Factor() else ZERO;

   170       if (more() && peek() != ')' && peek() != '|') Factor() else ONE;

    56 

   183     while (more() && peek() == '?') {

   184       eat('?') ;

   185       b = ALT(b, ONE) ;

   186     }

   187     while (more() && peek() == '+') {

   188       eat('+') ;

   189       b = SEQ(b, STAR(b)) ;

   190     }

    62       case '(' => { eat('(') ; val r = Regex(); eat(')') ; r }

   196       case '(' => { eat('(') ; val r = Regex(); eat(')') ; RECD("",r) }

   197       case '.' => { eat('.'); ANYCHAR }

    72   val s = line.split("\\t+")(1)

   207   if (line.head == '#') "#" else

    73   s + ":   " + Parser(s).Regex().toString

   208     {

    74 }

   209       val line_split = line.split("\\t+")

    75 

   210       val reg_str = line_split(1)

    76 

   211       val reg = RECD("", Parser(reg_str).Regex())

    77 val filename = "../tests/forced-assoc.txt"

   212       val in_str = if (line_split(2) == "-") "" else line_split(2)

   213       val res_str = line_split(3)

   214       val our_val = lexing(reg, in_str)

   215       val our_result = env2(our_val, reg, 0)._1.mkString("") 

   216       if (our_result != res_str) 

   217         { 

   218           reg_str + ":   " + 

   219           reg.toString + ": " + 

   220           in_str + "   \n " + 

   221           our_result +  

   222           " => \n" + res_str + " ! " +

   223           our_val + ":" + reg + "\n" 

   224         }

   225       else "*"

   226     }

   227 }

   228 

   229 

   230 //val filename = "../tests/forced-assoc.txt"

   231 //val filename = "../tests/left-assoc.txt"

   232 //val filename = "../tests/right-assoc.txt"

   233 //val filename = "../tests/class.txt"

   234 //val filename = "../tests/basic3.txt"

   235 //val filename = "../tests/totest.txt"

   236 //val filename = "../tests/repetition2.txt"

   237 //val filename = "../tests/osx-bsd-critical.txt"

   238 val filename = "../tests/nullsub3.txt"

    81 filelines.foreach((s: String) => println(process(s)))

   242 filelines.foreach((s: String) => print(process(s)))

    82 

   243