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solutions/cw4/lexer.sc
changeset 920 7af2eea19646
parent 894 02ef5c3abc51
child 959 64ec1884d860
equal deleted inserted replaced
919:53f08d873e09 920:7af2eea19646 
     1 import scala.language.implicitConversions    
     1 // Lexer from CW2 with additions to the rules
 
     2 import scala.language.reflectiveCalls
 
     2 //============================================
 
     3 
     3 
     4 // Rexp
 
     4 // Rexp
 
     5 abstract class Rexp
 
     5 abstract class Rexp
 
     6 case object ZERO extends Rexp
 
     6 case object ZERO extends Rexp
 
     7 case object ONE extends Rexp
 
     7 case object ONE extends Rexp
 
    25 case class Right(v: Val) extends Val
 
    25 case class Right(v: Val) extends Val
 
    26 case class Stars(vs: List[Val]) extends Val
 
    26 case class Stars(vs: List[Val]) extends Val
 
    27 case class Rec(x: String, v: Val) extends Val
 
    27 case class Rec(x: String, v: Val) extends Val
 
    28 
    28 
    29 
    29 
    30 // Convenience typing
 
    30 // Convenience for typing
 
    31 def charlist2rexp(s : List[Char]): Rexp = s match {
 
    31 def charlist2rexp(s : List[Char]): Rexp = s match {
 
    32   case Nil => ONE
 
    32   case Nil => ONE
 
    33   case c::Nil => CHAR(c)
 
    33   case c::Nil => CHAR(c)
 
    34   case c::s => SEQ(CHAR(c), charlist2rexp(s))
 
    34   case c::s => SEQ(CHAR(c), charlist2rexp(s))
 
    35 }
 
    35 }
 
    36 
    36 
    37 implicit def string2rexp(s : String) : Rexp = 
    37 implicit def string2rexp(s : String) : Rexp = 
    38   charlist2rexp(s.toList)
 
    38   charlist2rexp(s.toList)
 
    39 
    39 
    40 implicit def RexpOps(r: Rexp) = new {
 
    40 extension (r: Rexp) {
 
    41   def | (s: Rexp) = ALT(r, s)
 
    41   def | (s: Rexp) = ALT(r, s)
 
    42   def % = STAR(r)
 
    42   def % = STAR(r)
 
    43   def ~ (s: Rexp) = SEQ(r, s)
 
    43   def ~ (s: Rexp) = SEQ(r, s)
 
    44 }
 
    44 }
 
    45 
    45 
    46 implicit def stringOps(s: String) = new {
 
    46 extension (s: String) {
 
    47   def | (r: Rexp) = ALT(s, r)
 
    47   def | (r: Rexp) = ALT(s, r)
 
    48   def | (r: String) = ALT(s, r)
 
    48   def | (r: String) = ALT(s, r)
 
    49   def % = STAR(s)
 
    49   def % = STAR(s)
 
    50   def ~ (r: Rexp) = SEQ(s, r)
 
    50   def ~ (r: Rexp) = SEQ(s, r)
 
    51   def ~ (r: String) = SEQ(s, r)
 
    51   def ~ (r: String) = SEQ(s, r)
 
    80   case STAR(r) => SEQ(der(c, r), STAR(r))
 
    80   case STAR(r) => SEQ(der(c, r), STAR(r))
 
    81 
    81 
    82   case RECD(_, r1) => der(c, r1)
 
    82   case RECD(_, r1) => der(c, r1)
 
    83   case RANGE(s) => if (s.contains(c)) ONE else ZERO 
    83   case RANGE(s) => if (s.contains(c)) ONE else ZERO 
    84   case PLUS(r1) => SEQ(der(c, r1), STAR(r1))
 
    84   case PLUS(r1) => SEQ(der(c, r1), STAR(r1))
 
    85   case OPTIONAL(r1) => ALT(der(c, r1), ZERO)
 
    85   case OPTIONAL(r1) => der(c, r1)
 
    86   case NTIMES(r, i) => 
    86   case NTIMES(r, i) => 
    87     if (i == 0) ZERO else SEQ(der(c, r), NTIMES(r, i - 1))
 
    87     if (i == 0) ZERO else SEQ(der(c, r), NTIMES(r, i - 1))
 
    88 }
 
    88 }
 
    89 
    89 
    90 // Flatten
 
    90 // Flatten
 
   117   case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))
 
   117   case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))
 
   118   case STAR(r) => Stars(Nil)
 
   118   case STAR(r) => Stars(Nil)
 
   119   case RECD(x, r) => Rec(x, mkeps(r))
 
   119   case RECD(x, r) => Rec(x, mkeps(r))
 
   120 
   120 
   121   case PLUS(r) => Stars(List(mkeps(r)))   // the first copy must match the empty string
 
   121   case PLUS(r) => Stars(List(mkeps(r)))   // the first copy must match the empty string
 
   122   case OPTIONAL(r) => Right(Empty)
 
   122   case OPTIONAL(r) => if (nullable(r)) Stars(List(mkeps(r))) else Stars(Nil) 
   123   case NTIMES(r, i) => Stars(List.fill(i)(mkeps(r)))
 
   123   case NTIMES(r, i) => Stars(List.fill(i)(mkeps(r)))
 
   124 }
 
   124 }
 
   125 
   125 
   126 // Inj
 
   126 // Inj
 
   127 def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {
 
   127 def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {
 
   134   case (CHAR(d), Empty) => Chr(c) 
   134   case (CHAR(d), Empty) => Chr(c) 
   135   case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
 
   135   case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
 
   136 
   136 
   137   case (RANGE(_), Empty) => Chr(c)
 
   137   case (RANGE(_), Empty) => Chr(c)
 
   138   case (PLUS(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
 
   138   case (PLUS(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
 
   139   case (OPTIONAL(r), Left(v1)) => Left(inj(r, c, v1))
 
   139   case (OPTIONAL(r), v1) => Stars(List(inj(r, c, v1)))
 
   140   case (NTIMES(r, n), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
 
   140   case (NTIMES(r, n), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
 
   141 }
 
   141 }
 
   142 
   142 
   143 // Rectification functions
 
   143 // Rectification functions
 
   144 def F_ID(v: Val): Val = v
 
   144 def F_ID(v: Val): Val = v
 
   197 }
 
   197 }
 
   198 
   198 
   199 def lexing_simp(r: Rexp, s: String) = env(lex_simp(r, s.toList))
 
   199 def lexing_simp(r: Rexp, s: String) = env(lex_simp(r, s.toList))
 
   200 
   200 
   201 // Language specific code
 
   201 // Language specific code
 
   202 val KEYWORD : Rexp = "while" | "if" | "then" | "else" | "do" | "for" | "to" | "true" | "false" | "read" | "write" | "skip" 
   202 // Language specific code
 
       
   203 val KEYWORD : Rexp = "while" | "if" | "then" | "else" | "do" | "for" | "upto" | "true" | "false" | "read" | "write" | "skip" | "break"
 
   203 val OP : Rexp = "+" | "-" | "*" | "%" | "/" | "==" | "!=" | ">" | "<" | ">=" | "<=" | ":=" | "&&" | "||"
 
   204 val OP : Rexp = "+" | "-" | "*" | "%" | "/" | "==" | "!=" | ">" | "<" | ">=" | "<=" | ":=" | "&&" | "||"
 
   204 val LET: Rexp = RANGE(('A' to 'Z').toSet ++ ('a' to 'z'))
 
   205 val LET: Rexp = RANGE(('A' to 'Z').toSet ++ ('a' to 'z').toSet)
 
   205 val SYM : Rexp = LET | RANGE(Set('.', '_', '>', '<', '=', ';', ',', ':'))
 
   206 val SYM : Rexp = RANGE(Set('.', '_', '>', '<', '=', ';', ',', ':', ')', '('))
 
   206 val PARENS : Rexp = "(" | "{" | ")" | "}"
 
   207 val PARENS : Rexp = "(" | "{" | ")" | "}"
 
   207 val SEMI : Rexp = ";"
 
   208 val SEMI : Rexp = ";"
 
   208 val WHITESPACE : Rexp = PLUS(" ") | "\n" | "\t" | "\r"
 
   209 val WHITESPACE : Rexp = PLUS(" ") | "\n" | "\t" | "\r"
 
   209 val DIGIT : Rexp = RANGE(('0' to '9').toSet)
 
   210 val DIGIT : Rexp = RANGE(('0' to '9').toSet)
 
   210 val DIGIT1 : Rexp = RANGE(('1' to '9').toSet)
 
   211 val DIGIT1 : Rexp = RANGE(('1' to '9').toSet)
 
   211 val STRING : Rexp = "\"" ~ (SYM | " " | "\\n" | DIGIT).% ~ "\""
 
   212 val STRING : Rexp = "\"" ~ (LET | SYM | DIGIT | " " | "\\n").% ~ "\""
 
   212 val ID : Rexp = LET ~ (LET | "_" | DIGIT).%
 
   213 val ID : Rexp = LET ~ (LET | "_" | DIGIT).%
 
   213 val NUM : Rexp = "0" | (DIGIT1 ~ DIGIT.%)
 
   214 val NUM : Rexp = "0" | (DIGIT1 ~ DIGIT.%)
 
   214 val EOL : Rexp = "\n" | "\r\n"
 
   215 val EOL : Rexp = "\n" | "\r\n"
 
   215 val COMMENT : Rexp = "//" ~ (SYM | PARENS | " " | DIGIT).% ~ EOL
 
   216 val COMMENT : Rexp = "//" ~ (LET | SYM | PARENS | " " | DIGIT).% ~ EOL 
   216 
   217 
   217 val WHILE_REGS = (("k" $ KEYWORD) | 
   218 val WHILE_REGS = (("k" $ KEYWORD) | 
   218                   ("o" $ OP) | 
   219                   ("o" $ OP) | 
   219                   ("str" $ STRING) |
 
   220                   ("str" $ STRING) |
 
   220                   ("p" $ PARENS) |
 
   221                   ("p" $ PARENS) |
 
   222                   ("w" $ WHITESPACE) | 
   223                   ("w" $ WHITESPACE) | 
   223                   ("i" $ ID) | 
   224                   ("i" $ ID) | 
   224                   ("n" $ NUM) |
 
   225                   ("n" $ NUM) |
 
   225 		  ("c" $ COMMENT)).%
 
   226 		  ("c" $ COMMENT)).%
 
   226 
   227 
       
   228 
       
   229 
   227 // Token
 
   230 // Token
 
   228 abstract class Token extends Serializable 
   231 abstract class Token extends Serializable 
   229 case class T_KEYWORD(s: String) extends Token
 
   232 case class T_KEYWORD(s: String) extends Token
 
   230 case class T_OP(s: String) extends Token
 
   233 case class T_OP(s: String) extends Token
 
   231 case class T_STRING(s: String) extends Token
 
   234 case class T_STRING(s: String) extends Token
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