--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/solutions/cw5/fun_tokens.sc Fri Nov 04 12:07:40 2022 +0000
@@ -0,0 +1,280 @@
+// A tokeniser for the Fun language
+//==================================
+//
+// call with
+//
+// amm fun_tokens.sc fact.fun
+//
+// amm fun_tokens.sc defs.fun
+//
+
+
+
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+abstract class Rexp
+case object ZERO extends Rexp
+case object ONE extends Rexp
+case class CHAR(c: Char) extends Rexp
+case class ALT(r1: Rexp, r2: Rexp) extends Rexp
+case class SEQ(r1: Rexp, r2: Rexp) extends Rexp
+case class STAR(r: Rexp) extends Rexp
+case class RECD(x: String, r: Rexp) extends Rexp
+
+abstract class Val
+case object Empty extends Val
+case class Chr(c: Char) extends Val
+case class Sequ(v1: Val, v2: Val) extends Val
+case class Left(v: Val) extends Val
+case class Right(v: Val) extends Val
+case class Stars(vs: List[Val]) extends Val
+case class Rec(x: String, v: Val) extends Val
+
+// some convenience for typing in regular expressions
+def charlist2rexp(s : List[Char]): Rexp = s match {
+ case Nil => ONE
+ case c::Nil => CHAR(c)
+ case c::s => SEQ(CHAR(c), charlist2rexp(s))
+}
+implicit def string2rexp(s : String) : Rexp =
+ charlist2rexp(s.toList)
+
+implicit def RexpOps(r: Rexp) = new {
+ def | (s: Rexp) = ALT(r, s)
+ def % = STAR(r)
+ def ~ (s: Rexp) = SEQ(r, s)
+}
+
+implicit def stringOps(s: String) = new {
+ def | (r: Rexp) = ALT(s, r)
+ def | (r: String) = ALT(s, r)
+ def % = STAR(s)
+ def ~ (r: Rexp) = SEQ(s, r)
+ def ~ (r: String) = SEQ(s, r)
+ def $ (r: Rexp) = RECD(s, r)
+}
+
+def nullable (r: Rexp) : Boolean = r match {
+ case ZERO => false
+ case ONE => true
+ case CHAR(_) => false
+ case ALT(r1, r2) => nullable(r1) || nullable(r2)
+ case SEQ(r1, r2) => nullable(r1) && nullable(r2)
+ case STAR(_) => true
+ case RECD(_, r1) => nullable(r1)
+}
+
+def der (c: Char, r: Rexp) : Rexp = r match {
+ case ZERO => ZERO
+ case ONE => ZERO
+ case CHAR(d) => if (c == d) ONE else ZERO
+ case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))
+ case SEQ(r1, r2) =>
+ if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))
+ else SEQ(der(c, r1), r2)
+ case STAR(r) => SEQ(der(c, r), STAR(r))
+ case RECD(_, r1) => der(c, r1)
+}
+
+
+// extracts a string from value
+def flatten(v: Val) : String = v match {
+ case Empty => ""
+ case Chr(c) => c.toString
+ case Left(v) => flatten(v)
+ case Right(v) => flatten(v)
+ case Sequ(v1, v2) => flatten(v1) + flatten(v2)
+ case Stars(vs) => vs.map(flatten).mkString
+ case Rec(_, v) => flatten(v)
+}
+
+// extracts an environment from a value;
+// used for tokenise a string
+def env(v: Val) : List[(String, String)] = v match {
+ case Empty => Nil
+ case Chr(c) => Nil
+ case Left(v) => env(v)
+ case Right(v) => env(v)
+ case Sequ(v1, v2) => env(v1) ::: env(v2)
+ case Stars(vs) => vs.flatMap(env)
+ case Rec(x, v) => (x, flatten(v))::env(v)
+}
+
+// The Injection Part of the lexer
+
+def mkeps(r: Rexp) : Val = r match {
+ case ONE => Empty
+ case ALT(r1, r2) =>
+ if (nullable(r1)) Left(mkeps(r1)) else Right(mkeps(r2))
+ case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))
+ case STAR(r) => Stars(Nil)
+ case RECD(x, r) => Rec(x, mkeps(r))
+}
+
+def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {
+ case (STAR(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
+ case (SEQ(r1, r2), Sequ(v1, v2)) => Sequ(inj(r1, c, v1), v2)
+ case (SEQ(r1, r2), Left(Sequ(v1, v2))) => Sequ(inj(r1, c, v1), v2)
+ case (SEQ(r1, r2), Right(v2)) => Sequ(mkeps(r1), inj(r2, c, v2))
+ case (ALT(r1, r2), Left(v1)) => Left(inj(r1, c, v1))
+ case (ALT(r1, r2), Right(v2)) => Right(inj(r2, c, v2))
+ case (CHAR(d), Empty) => Chr(c)
+ case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
+ case _ => { println ("Injection error") ; sys.exit(-1) }
+}
+
+// some "rectification" functions for simplification
+def F_ID(v: Val): Val = v
+def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))
+def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))
+def F_ALT(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {
+ case Right(v) => Right(f2(v))
+ case Left(v) => Left(f1(v))
+}
+def F_SEQ(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {
+ case Sequ(v1, v2) => Sequ(f1(v1), f2(v2))
+}
+def F_SEQ_Empty1(f1: Val => Val, f2: Val => Val) =
+ (v:Val) => Sequ(f1(Empty), f2(v))
+def F_SEQ_Empty2(f1: Val => Val, f2: Val => Val) =
+ (v:Val) => Sequ(f1(v), f2(Empty))
+def F_RECD(f: Val => Val) = (v:Val) => v match {
+ case Rec(x, v) => Rec(x, f(v))
+}
+def F_ERROR(v: Val): Val = throw new Exception("error")
+
+def simp(r: Rexp): (Rexp, Val => Val) = r match {
+ case ALT(r1, r2) => {
+ val (r1s, f1s) = simp(r1)
+ val (r2s, f2s) = simp(r2)
+ (r1s, r2s) match {
+ case (ZERO, _) => (r2s, F_RIGHT(f2s))
+ case (_, ZERO) => (r1s, F_LEFT(f1s))
+ case _ => if (r1s == r2s) (r1s, F_LEFT(f1s))
+ else (ALT (r1s, r2s), F_ALT(f1s, f2s))
+ }
+ }
+ case SEQ(r1, r2) => {
+ val (r1s, f1s) = simp(r1)
+ val (r2s, f2s) = simp(r2)
+ (r1s, r2s) match {
+ case (ZERO, _) => (ZERO, F_ERROR)
+ case (_, ZERO) => (ZERO, F_ERROR)
+ case (ONE, _) => (r2s, F_SEQ_Empty1(f1s, f2s))
+ case (_, ONE) => (r1s, F_SEQ_Empty2(f1s, f2s))
+ case _ => (SEQ(r1s,r2s), F_SEQ(f1s, f2s))
+ }
+ }
+ case RECD(x, r1) => {
+ val (r1s, f1s) = simp(r1)
+ (RECD(x, r1s), F_RECD(f1s))
+ }
+ case r => (r, F_ID)
+}
+
+// lexing functions including simplification
+def lex_simp(r: Rexp, s: List[Char]) : Val = s match {
+ case Nil => if (nullable(r)) mkeps(r) else { println ("Lexing Error") ; sys.exit(-1) }
+ case c::cs => {
+ val (r_simp, f_simp) = simp(der(c, r))
+ inj(r, c, f_simp(lex_simp(r_simp, cs)))
+ }
+}
+
+def lexing_simp(r: Rexp, s: String) = env(lex_simp(r, s.toList))
+
+
+// The Lexing Rules for the Fun Language
+
+def PLUS(r: Rexp) = r ~ r.%
+def OPT(r: Rexp) = r | ONE
+
+val SYM = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" |
+ "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" |
+ "w" | "x" | "y" | "z" | "A" | "B" | "C" | "D" |"E" | "F" | "G" |
+ "H" | "I" | "J" | "K" |"L" | "M" | "N" |
+ "O" | "P" | "Q" | "R" |"S" | "T" | "U" |
+ "V" | "W" | "X" | "Y" | "Z" | "_" | ":"
+val DIGIT = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
+val ID = SYM ~ (SYM | DIGIT).%
+val NUM = PLUS(DIGIT)
+val FNUM = OPT("-") ~ NUM ~ "." ~ NUM
+val KEYWORD : Rexp = "if" | "then" | "else" | "def" | "val"
+val TYPE : Rexp = "Void" | "Int" | "Double"
+val SEMI: Rexp = ";"
+val COLON: Rexp = ":"
+val COMMA: Rexp = ","
+val OP: Rexp = "=" | "==" | "-" | "+" | "*" | "!=" | "<" | ">" | "<=" | ">=" | "%" | "/"
+val WHITESPACE = PLUS(" " | "\n" | "\t" | "\r")
+val RPAREN: Rexp = ")" | "}"
+val LPAREN: Rexp = "(" | "{"
+val ALL = SYM | DIGIT | OP | " " | ":" | ";" | "-" | "." | "\"" | "=" | "," | "(" | ")" | "{" | "}"
+val ALL2 = ALL | "\n"
+val COMMENT = ("/*" ~ ALL2.% ~ "*/") | ("//" ~ ALL.% ~ "\n")
+
+val CHR :Rexp = "'" ~ (ALL | "\\n") ~ "'"
+
+
+val FUN_REGS = (("k" $ KEYWORD) |
+ ("t" $ TYPE) |
+ ("i" $ ID) |
+ ("ch" $ CHR) |
+ ("o" $ OP) |
+ ("n" $ NUM) |
+ ("f" $ FNUM) |
+ ("s" $ SEMI) |
+ ("co" $ COLON) |
+ ("c" $ COMMA) |
+ ("pl" $ LPAREN) |
+ ("pr" $ RPAREN) |
+ ("w" $ (WHITESPACE | COMMENT))).%
+
+
+
+// The tokens for the Fun language
+
+abstract class Token extends Serializable
+case object T_SEMI extends Token
+case object T_COMMA extends Token
+case object T_COLON extends Token
+case object T_LPAREN extends Token
+case object T_RPAREN extends Token
+case class T_ID(s: String) extends Token
+case class T_FID(s: String) extends Token
+case class T_OP(s: String) extends Token
+case class T_NUM(n: Int) extends Token
+case class T_FNUM(x: Double) extends Token
+case class T_KWD(s: String) extends Token
+case class T_TY(s: String) extends Token
+case class T_CHR(i: Int) extends Token
+
+val token : PartialFunction[(String, String), Token] = {
+ case ("k", s) => T_KWD(s)
+ case ("t", s) => T_TY(s)
+ case ("i", s) => T_ID(s)
+ case ("o", s) => T_OP(s)
+ case ("n", s) => T_NUM(s.toInt)
+ case ("ch", s) => if (s == "'\\n'") T_CHR(10) else T_CHR(s(1).toInt)
+ case ("f", s) => T_FNUM(s.toDouble)
+ case ("s", _) => T_SEMI
+ case ("c", _) => T_COMMA
+ case ("co", _) => T_COLON
+ case ("pl", _) => T_LPAREN
+ case ("pr", _) => T_RPAREN
+}
+
+
+def tokenise(s: String) : List[Token] = {
+ val tks = lexing_simp(FUN_REGS, s).collect(token)
+ if (tks.length != 0) tks
+ else { println (s"Tokenise Error") ; sys.exit(-1) }
+}
+
+//import ammonite.ops._
+
+//@doc("Tokenising a file.")
+@main
+def main(fname: String) = {
+ println(tokenise(os.read(os.pwd / fname)))
+}