1 // A parser for the Fun language

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

     3 //

     4 // call with 

     5 //

     6 //     amm fun_parser.sc fact.fun

     7 //

     8 //     amm fun_parser.sc defs.fun

     9 //

    10 // this will generate a parse-tree from a list

    11 // of tokens

    12 

    13 import scala.language.implicitConversions    

    14 import scala.language.reflectiveCalls

    15 

    16 import $file.fun_tokens, fun_tokens._ 

    17 

    18 

    19 // Parser combinators

    20 //    type parameter I needs to be of Seq-type

    21 //

    22 abstract class Parser[I, T](implicit ev: I => Seq[_]) {

    23   def parse(ts: I): Set[(T, I)]

    24 

    25   def parse_single(ts: I) : T = 

    26     parse(ts).partition(_._2.isEmpty) match {

    27       case (good, _) if !good.isEmpty => good.head._1

    28       case (good, err) if err.isEmpty => {

    29         println (s"Parse Error\n $good \n $err") ; sys.exit(-1) }

    30       case (_, err) => { 

    31 	println (s"Parse Error\n${err.minBy(_._2.length)}") ; sys.exit(-1) }

    32     }

    33 }

    34 

    35 // convenience for writing grammar rules

    36 case class ~[+A, +B](_1: A, _2: B)

    37 

    38 class SeqParser[I, T, S](p: => Parser[I, T], 

    39                          q: => Parser[I, S])(implicit ev: I => Seq[_]) extends Parser[I, ~[T, S]] {

    40   def parse(sb: I) = 

    41     for ((head1, tail1) <- p.parse(sb); 

    42          (head2, tail2) <- q.parse(tail1)) yield (new ~(head1, head2), tail2)

    43 }

    44 

    45 class AltParser[I, T](p: => Parser[I, T], 

    46                       q: => Parser[I, T])(implicit ev: I => Seq[_]) extends Parser[I, T] {

    47   def parse(sb: I) = p.parse(sb) ++ q.parse(sb)   

    48 }

    49 

    50 class FunParser[I, T, S](p: => Parser[I, T], 

    51                          f: T => S)(implicit ev: I => Seq[_]) extends Parser[I, S] {

    52   def parse(sb: I) = 

    53     for ((head, tail) <- p.parse(sb)) yield (f(head), tail)

    54 }

    55 

    56 // convenient combinators

    57 implicit def ParserOps[I, T](p: Parser[I, T])(implicit ev: I => Seq[_]) = new {

    58   def || (q : => Parser[I, T]) = new AltParser[I, T](p, q)

    59   def ==>[S] (f: => T => S) = new FunParser[I, T, S](p, f)

    60   def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q)

    61 }

    62 

    63 def ListParser[I, T, S](p: => Parser[I, T], 

    64                         q: => Parser[I, S])(implicit ev: I => Seq[_]): Parser[I, List[T]] = {

    65   (p ==> ((s) => List(s))) ||

    66   (p ~ q ~ ListParser(p, q)) ==> { case x ~ _ ~ z => x :: z : List[T] }

    67 }

    68 

    69 case class TokParser(tok: Token) extends Parser[List[Token], Token] {

    70   def parse(ts: List[Token]) = ts match {

    71     case t::ts if (t == tok) => Set((t, ts)) 

    72     case _ => Set()

    73   }

    74 }

    75 

    76 implicit def token2tparser(t: Token) = TokParser(t)

    77 

    78 implicit def TokOps(t: Token) = new {

    79   def || (q : => Parser[List[Token], Token]) = new AltParser[List[Token], Token](t, q)

    80   def ==>[S] (f: => Token => S) = new FunParser[List[Token], Token, S](t, f)

    81   def ~[S](q : => Parser[List[Token], S]) = new SeqParser[List[Token], Token, S](t, q)

    82 }

    83 

    84 case object EmptyParser extends Parser[List[Token], String] {

    85   def parse(ts: List[Token]) = Set(("", ts))

    86 }

    87 

    88 case object NumParser extends Parser[List[Token], Int] {

    89   def parse(ts: List[Token]) = ts match {

    90     case T_NUM(n)::ts => Set((n, ts)) 

    91     case _ => Set ()

    92   }

    93 }

    94 

    95 case object FNumParser extends Parser[List[Token], Double] {

    96   def parse(ts: List[Token]) = ts match {

    97     case T_FNUM(x)::ts => Set((x, ts)) 

    98     case _ => Set()

    99   }

   100 }

   101 

   102 case object IdParser extends Parser[List[Token], String] {

   103   def parse(ts: List[Token]) = ts match {

   104     case T_ID(s)::ts => Set((s, ts)) 

   105     case _ => Set ()

   106   }

   107 }

   108 

   109 case object CharConstParser extends Parser[List[Token], Int] {

   110   def parse(ts: List[Token]) = ts match {

   111     case T_CHR(c)::ts => Set((c, ts)) 

   112     case _ => Set ()

   113   }

   114 }

   115 

   116 case object TyParser extends Parser[List[Token], String] {

   117   def parse(ts: List[Token]) = ts match {

   118     case T_TY(s)::ts => Set((s, ts)) 

   119     case _ => Set ()

   120   }

   121 }

   122 

   123 

   124 // Abstract syntax trees for the Fun language

   125 abstract class Exp 

   126 abstract class BExp 

   127 abstract class Decl 

   128 

   129 case class Def(name: String, args: List[(String, String)], ty: String, body: Exp) extends Decl

   130 case class Main(e: Exp) extends Decl

   131 case class Const(name: String, v: Int) extends Decl

   132 case class FConst(name: String, x: Double) extends Decl

   133 

   134 case class Call(name: String, args: List[Exp]) extends Exp

   135 case class If(a: BExp, e1: Exp, e2: Exp) extends Exp

   136 case class Var(s: String) extends Exp

   137 case class Num(i: Int) extends Exp     // integer numbers

   138 case class FNum(i: Double) extends Exp  // floating numbers

   139 case class ChConst(c: Int) extends Exp // char constant

   140 case class Aop(o: String, a1: Exp, a2: Exp) extends Exp

   141 case class Sequence(e1: Exp, e2: Exp) extends Exp

   142 case class Bop(o: String, a1: Exp, a2: Exp) extends BExp

   143 

   144 

   145 // arithmetic expressions (there needs to be an F in the SEMICOLON case)

   146 lazy val Exp: Parser[List[Token], Exp] = 

   147   (T_KWD("if") ~ BExp ~ T_KWD("then") ~ Exp ~ T_KWD("else") ~ Exp) ==>

   148     { case _ ~ x ~ _ ~ y ~ _ ~ z => If(x, y, z): Exp } ||

   149   (F ~ T_SEMI ~ Exp) ==> { case x ~ _ ~ y => Sequence(x, y): Exp } || L

   150 lazy val L: Parser[List[Token], Exp] = 

   151   (T ~ T_OP("+") ~ Exp) ==> { case x ~ _ ~ z => Aop("+", x, z): Exp } ||

   152   (T ~ T_OP("-") ~ Exp) ==> { case x ~ _ ~ z => Aop("-", x, z): Exp } || T  

   153 lazy val T: Parser[List[Token], Exp] = 

   154   (F ~ T_OP("*") ~ T) ==> { case x ~ _ ~ z => Aop("*", x, z): Exp } || 

   155   (F ~ T_OP("/") ~ T) ==> { case x ~ _ ~ z => Aop("/", x, z): Exp } || 

   156   (F ~ T_OP("%") ~ T) ==> { case x ~ _ ~ z => Aop("%", x, z): Exp } || F

   157 lazy val F: Parser[List[Token], Exp] = 

   158   (IdParser ~ T_LPAREN ~ T_RPAREN) ==> { case x ~ _ ~ _ => Call(x, Nil): Exp } ||

   159   (IdParser ~ T_LPAREN ~ ListParser(Exp, T_COMMA) ~ T_RPAREN) ==> { case x ~ _ ~ z ~ _ => Call(x, z): Exp } ||

   160   (T_LPAREN ~ Exp ~ T_RPAREN) ==> { case _ ~ y ~ _ => y: Exp } || 

   161   IdParser ==> { case x => Var(x): Exp } || 

   162   NumParser ==> { case x => Num(x): Exp } ||

   163   CharConstParser ==> { case x => ChConst(x): Exp } ||

   164   FNumParser ==> { case x => FNum(x): Exp }

   165 

   166 // boolean expressions

   167 lazy val BExp: Parser[List[Token], BExp] = 

   168   (Exp ~ T_OP("==") ~ Exp) ==> { case x ~ _ ~ z => Bop("==", x, z): BExp } || 

   169   (Exp ~ T_OP("!=") ~ Exp) ==> { case x ~ _ ~ z => Bop("!=", x, z): BExp } || 

   170   (Exp ~ T_OP("<") ~ Exp)  ==> { case x ~ _ ~ z => Bop("<",  x, z): BExp } || 

   171   (Exp ~ T_OP(">") ~ Exp)  ==> { case x ~ _ ~ z => Bop("<",  z, x): BExp } || 

   172   (Exp ~ T_OP("<=") ~ Exp) ==> { case x ~ _ ~ z => Bop("<=", x, z): BExp } || 

   173   (Exp ~ T_OP("=>") ~ Exp) ==> { case x ~ _ ~ z => Bop("<=", z, x): BExp } ||

   174   (T_LPAREN ~ BExp ~ T_RPAREN) ==> { case _ ~ b ~ _ => b : BExp } 

   175 

   176 lazy val Arg : Parser[List[Token], (String, String)] = 

   177   (IdParser ~ T_COLON ~ TyParser) ==> { case x ~ _ ~ ty => (x, ty) }  

   178 

   179 lazy val Defn: Parser[List[Token], Decl] = {

   180    (T_KWD("def") ~ IdParser ~ T_LPAREN ~ T_RPAREN ~ T_COLON ~ TyParser ~ T_OP("=") ~ Exp) ==>

   181      { case _ ~ y ~ _ ~ _ ~ _~ ty ~ _ ~ r => Def(y, Nil, ty, r): Decl } ||

   182    (T_KWD("def") ~ IdParser ~ T_LPAREN ~ ListParser(Arg, T_COMMA) ~ T_RPAREN ~ T_COLON ~ TyParser ~ T_OP("=") ~ Exp) ==>

   183      { case _ ~ y ~ _ ~ w ~ _ ~ _~ ty ~ _ ~ r => Def(y, w, ty, r): Decl }

   184 }

   185 

   186 lazy val Const_decl: Parser[List[Token], Decl] =

   187    (T_KWD("val") ~ Arg ~ T_OP("=") ~ NumParser) ==>

   188      { case _ ~ x ~ _ ~ v => Const(x._1, v): Decl } ||

   189    (T_KWD("val") ~ Arg ~ T_OP("=") ~ FNumParser) ==>

   190      { case _ ~ x ~ _ ~ v => FConst(x._1, v): Decl } 

   191 

   192 lazy val Prog: Parser[List[Token], List[Decl]] =

   193   (Defn ~ T_SEMI ~ Prog) ==> { case x ~ _ ~ z => x :: z : List[Decl] } ||

   194   (Const_decl ~ T_SEMI ~ Prog) ==> { case x ~ _ ~ z => x :: z : List[Decl] } ||

   195   (Exp ==> ((s) => List(Main(s)) : List[Decl]))

   196 

   197 

   198 

   199 // Reading tokens and Writing parse trees

   200 

   201 //import ammonite.ops._

   202 

   203 def parse_tks(tks: List[Token]) : List[Decl] = {

   204   //println(Prog.parse(tks))

   205   Prog.parse_single(tks)

   206 }

   207 

   208 //@doc("Parses a file.")

   209 @main

   210 def main(fname: String) : Unit = {

   211   val tks = tokenise(os.read(os.pwd / fname))

   212   println(parse_tks(tks))

   213 }

   214 

   215