1 // A tokeniser for the Fun language

     2 //==================================

     3 //

     4 // call with 

     5 //

     6 //     scala fun_tokens.scala fact.fun

     7 //

     8 //     scala fun_tokens.scala defs.fun

     9 //

    10 // this will generate a .tks file that can be deserialised back

    11 // into a list of tokens

    12 // you can add -Xno-patmat-analysis in order to get rid of the

    13 // match-not-exhaustive warning

    14 

    15 object Fun_Tokens {

    16 

    17 import scala.language.implicitConversions    

    18 import scala.language.reflectiveCalls 

    19 

    20 abstract class Rexp 

    21 case object ZERO extends Rexp

    22 case object ONE extends Rexp

    23 case class CHAR(c: Char) extends Rexp

    24 case class ALT(r1: Rexp, r2: Rexp) extends Rexp 

    25 case class SEQ(r1: Rexp, r2: Rexp) extends Rexp 

    26 case class STAR(r: Rexp) extends Rexp 

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

    28   

    29 abstract class Val

    30 case object Empty extends Val

    31 case class Chr(c: Char) extends Val

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

    33 case class Left(v: Val) extends Val

    34 case class Right(v: Val) extends Val

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

    36 case class Rec(x: String, v: Val) extends Val

    37    

    38 // some convenience for typing in regular expressions

    39 def charlist2rexp(s : List[Char]): Rexp = s match {

    40   case Nil => ONE

    41   case c::Nil => CHAR(c)

    42   case c::s => SEQ(CHAR(c), charlist2rexp(s))

    43 }

    44 implicit def string2rexp(s : String) : Rexp = 

    45   charlist2rexp(s.toList)

    46 

    47 implicit def RexpOps(r: Rexp) = new {

    48   def | (s: Rexp) = ALT(r, s)

    49   def % = STAR(r)

    50   def ~ (s: Rexp) = SEQ(r, s)

    51 }

    52 

    53 implicit def stringOps(s: String) = new {

    54   def | (r: Rexp) = ALT(s, r)

    55   def | (r: String) = ALT(s, r)

    56   def % = STAR(s)

    57   def ~ (r: Rexp) = SEQ(s, r)

    58   def ~ (r: String) = SEQ(s, r)

    59   def $ (r: Rexp) = RECD(s, r)

    60 }

    61 

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

    63   case ZERO => false

    64   case ONE => true

    65   case CHAR(_) => false

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

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

    68   case STAR(_) => true

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

    70 }

    71 

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

    73   case ZERO => ZERO

    74   case ONE => ZERO

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

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

    77   case SEQ(r1, r2) => 

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

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

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

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

    82 }

    83 

    84 

    85 // extracts a string from value

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

    87   case Empty => ""

    88   case Chr(c) => c.toString

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

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

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

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

    93   case Rec(_, v) => flatten(v)

    94 }

    95 

    96 // extracts an environment from a value;

    97 // used for tokenise a string

    98 def env(v: Val) : List[(String, String)] = v match {

    99   case Empty => Nil

   100   case Chr(c) => Nil

   101   case Left(v) => env(v)

   102   case Right(v) => env(v)

   103   case Sequ(v1, v2) => env(v1) ::: env(v2)

   104   case Stars(vs) => vs.flatMap(env)

   105   case Rec(x, v) => (x, flatten(v))::env(v)

   106 }

   107 

   108 // The Injection Part of the lexer

   109 

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

   111   case ONE => Empty

   112   case ALT(r1, r2) => 

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

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

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

   116   case RECD(x, r) => Rec(x, mkeps(r))

   117 }

   118 

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

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

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

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

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

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

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

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

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

   128   case _ => { println ("Injection error") ; sys.exit(-1) } 

   129 }

   130 

   131 // some "rectification" functions for simplification

   132 def F_ID(v: Val): Val = v

   133 def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))

   134 def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))

   135 def F_ALT(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {

   136   case Right(v) => Right(f2(v))

   137   case Left(v) => Left(f1(v))

   138 }

   139 def F_SEQ(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {

   140   case Sequ(v1, v2) => Sequ(f1(v1), f2(v2))

   141 }

   142 def F_SEQ_Empty1(f1: Val => Val, f2: Val => Val) = 

   143   (v:Val) => Sequ(f1(Empty), f2(v))

   144 def F_SEQ_Empty2(f1: Val => Val, f2: Val => Val) = 

   145   (v:Val) => Sequ(f1(v), f2(Empty))

   146 def F_RECD(f: Val => Val) = (v:Val) => v match {

   147   case Rec(x, v) => Rec(x, f(v))

   148 }

   149 def F_ERROR(v: Val): Val = throw new Exception("error")

   150 

   151 def simp(r: Rexp): (Rexp, Val => Val) = r match {

   152   case ALT(r1, r2) => {

   153     val (r1s, f1s) = simp(r1)

   154     val (r2s, f2s) = simp(r2)

   155     (r1s, r2s) match {

   156       case (ZERO, _) => (r2s, F_RIGHT(f2s))

   157       case (_, ZERO) => (r1s, F_LEFT(f1s))

   158       case _ => if (r1s == r2s) (r1s, F_LEFT(f1s))

   159                 else (ALT (r1s, r2s), F_ALT(f1s, f2s)) 

   160     }

   161   }

   162   case SEQ(r1, r2) => {

   163     val (r1s, f1s) = simp(r1)

   164     val (r2s, f2s) = simp(r2)

   165     (r1s, r2s) match {

   166       case (ZERO, _) => (ZERO, F_ERROR)

   167       case (_, ZERO) => (ZERO, F_ERROR)

   168       case (ONE, _) => (r2s, F_SEQ_Empty1(f1s, f2s))

   169       case (_, ONE) => (r1s, F_SEQ_Empty2(f1s, f2s))

   170       case _ => (SEQ(r1s,r2s), F_SEQ(f1s, f2s))

   171     }

   172   }

   173   case RECD(x, r1) => {

   174     val (r1s, f1s) = simp(r1)

   175     (RECD(x, r1s), F_RECD(f1s))

   176   }

   177   case r => (r, F_ID)

   178 }

   179 

   180 // lexing functions including simplification

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

   182   case Nil => if (nullable(r)) mkeps(r) else { println ("Lexing Error") ; sys.exit(-1) } 

   183   case c::cs => {

   184     val (r_simp, f_simp) = simp(der(c, r))

   185     inj(r, c, f_simp(lex_simp(r_simp, cs)))

   186   }

   187 }

   188 

   189 def lexing_simp(r: Rexp, s: String) = env(lex_simp(r, s.toList))

   190 

   191 

   192 // The Lexing Rules for the Fun Language

   193 

   194 def PLUS(r: Rexp) = r ~ r.%

   195 

   196 val SYM = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | 

   197           "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" | 

   198           "w" | "x" | "y" | "z" | "T" | "_"

   199 val DIGIT = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"

   200 val ID = SYM ~ (SYM | DIGIT).% 

   201 val NUM = PLUS(DIGIT)

   202 val KEYWORD : Rexp = "if" | "then" | "else" | "write" | "def"

   203 val SEMI: Rexp = ";"

   204 val OP: Rexp = "=" | "==" | "-" | "+" | "*" | "!=" | "<" | ">" | "<=" | ">=" | "%" | "/"

   205 val WHITESPACE = PLUS(" " | "\n" | "\t")

   206 val RPAREN: Rexp = ")"

   207 val LPAREN: Rexp = "("

   208 val COMMA: Rexp = ","

   209 val ALL = SYM | DIGIT | OP | " " | ":" | ";" | "\"" | "=" | "," | "(" | ")"

   210 val ALL2 = ALL | "\n"

   211 val COMMENT = ("/*" ~ ALL2.% ~ "*/") | ("//" ~ ALL.% ~ "\n")

   212 

   213 

   214 val FUN_REGS = (("k" $ KEYWORD) | 

   215                   ("i" $ ID) | 

   216                   ("o" $ OP) | 

   217                   ("n" $ NUM) | 

   218                   ("s" $ SEMI) | 

   219                   ("c" $ COMMA) |

   220                   ("pl" $ LPAREN) |

   221                   ("pr" $ RPAREN) |

   222                   ("w" $ (WHITESPACE | COMMENT))).%

   223 

   224 

   225 

   226 // The tokens for the Fun language

   227 

   228 import java.io._

   229 

   230 abstract class Token extends Serializable 

   231 case object T_SEMI extends Token

   232 case object T_COMMA extends Token

   233 case object T_LPAREN extends Token

   234 case object T_RPAREN extends Token

   235 case class T_ID(s: String) extends Token

   236 case class T_OP(s: String) extends Token

   237 case class T_NUM(n: Int) extends Token

   238 case class T_KWD(s: String) extends Token

   239 

   240 val token : PartialFunction[(String, String), Token] = {

   241   case ("k", s) => T_KWD(s)

   242   case ("i", s) => T_ID(s)

   243   case ("o", s) => T_OP(s)

   244   case ("n", s) => T_NUM(s.toInt)

   245   case ("s", _) => T_SEMI

   246   case ("c", _) => T_COMMA

   247   case ("pl", _) => T_LPAREN

   248   case ("pr", _) => T_RPAREN

   249 }

   250 

   251 

   252 def tokenise(s: String) : List[Token] = {

   253   val tks = lexing_simp(FUN_REGS, s).collect(token)

   254   if (tks.length != 0) tks

   255   else { println (s"Tokenise Error") ; sys.exit(-1) }     

   256 }

   257 

   258 def serialise[T](fname: String, data: T) = {

   259   import scala.util.Using

   260   Using(new ObjectOutputStream(new FileOutputStream(fname))) {

   261     out => out.writeObject(data)

   262   }

   263 }

   264 

   265 def main(args: Array[String]) : Unit = {

   266   val fname = args(0)

   267   val tname = fname.stripSuffix(".fun") ++ ".tks"

   268   val file = io.Source.fromFile(fname).mkString

   269   serialise(tname, tokenise(file))

   270 }

   271 

   272 

   273 }