--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/Attic/token.scala Mon Sep 07 12:18:07 2020 +0100
@@ -0,0 +1,342 @@
+// A simple lexer inspired by work of Sulzmann & Lu
+//==================================================
+
+
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+// regular expressions including records
+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
+
+// values
+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))
+}
+
+// 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
+ { throw new Exception("lexing error") }
+ 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 Range(s : List[Char]) : Rexp = s match {
+ case Nil => ZERO
+ case c::Nil => CHAR(c)
+ case c::s => ALT(CHAR(c), Range(s))
+}
+def RANGE(s: String) = Range(s.toList)
+
+val SYM = RANGE("ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz_")
+val DIGIT = RANGE("0123456789")
+val ID = SYM ~ (SYM | DIGIT).%
+val NUM = PLUS(DIGIT)
+val KEYWORD : Rexp = "skip" | "while" | "do" | "if" | "then" | "else" | "read" | "write"
+val SEMI: Rexp = ";"
+val OP: Rexp = ":=" | "=" | "-" | "+" | "*" | "!=" | "<" | ">"
+val WHITESPACE = PLUS(" " | "\n" | "\t")
+val RPAREN: Rexp = "{"
+val LPAREN: Rexp = "}"
+val STRING: Rexp = "\"" ~ SYM.% ~ "\""
+
+
+val WHILE_REGS = (("k" $ KEYWORD) |
+ ("i" $ ID) |
+ ("o" $ OP) |
+ ("n" $ NUM) |
+ ("s" $ SEMI) |
+ ("str" $ STRING) |
+ ("p" $ (LPAREN | RPAREN)) |
+ ("w" $ WHITESPACE)).%
+
+
+// Two Simple While Tests
+//========================
+
+println("test: read n")
+
+val prog0 = """read n"""
+println(lexing_simp(WHILE_REGS, prog0))
+
+println("test: read n; write n ")
+
+val prog1 = """read n; write n"""
+println(lexing_simp(WHILE_REGS, prog1))
+
+
+// Bigger Tests
+//==============
+
+// escapes strings and prints them out as "", "\n" and so on
+def esc(raw: String): String = {
+ import scala.reflect.runtime.universe._
+ Literal(Constant(raw)).toString
+}
+
+def escape(tks: List[(String, String)]) =
+ tks.map{ case (s1, s2) => (s1, esc(s2))}
+
+val prog2 = """
+write "Fib";
+read n;
+minus1 := 0;
+minus2 := 1;
+while n > 0 do {
+ temp := minus2;
+ minus2 := minus1 + minus2;
+ minus1 := temp;
+ n := n - 1
+};
+write "Result";
+write minus2
+"""
+
+println("Tokens for Fib")
+println(escape(lexing_simp(WHILE_REGS, prog2)).mkString("\n"))
+
+
+
+val prog3 = """
+start := 1000;
+x := start;
+y := start;
+z := start;
+while 0 < x do {
+ while 0 < y do {
+ while 0 < z do {
+ z := z - 1
+ };
+ z := start;
+ y := y - 1
+ };
+ y := start;
+ x := x - 1
+}
+"""
+
+println("Tokens for Loops")
+println(escape(lexing_simp(WHILE_REGS, prog3)).mkString("\n"))
+
+
+
+
+
+
+
+// The tokens for the WHILE language
+import java.io._
+
+abstract class Token extends Serializable
+case object T_SEMI 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_OP(s: String) extends Token
+case class T_NUM(n: Int) extends Token
+case class T_KWD(s: String) extends Token
+case class T_STR(s: String) extends Token
+
+val token : PartialFunction[(String, String), Token] = {
+ case ("s", _) => T_SEMI
+ case ("p", "{") => T_LPAREN
+ case ("p", "}") => T_RPAREN
+ case ("i", s) => T_ID(s)
+ case ("o", s) => T_OP(s)
+ case ("n", s) => T_NUM(s.toInt)
+ case ("k", s) => T_KWD(s)
+ case ("str", s) => T_STR(s)
+}
+
+def tokenise(s: String) : List[Token] =
+ lexing_simp(WHILE_REGS, s).collect(token)
+
+tokenise(prog2)
+tokenise(prog3)
+
+
+object Lexer extends App {
+
+ val fname = "/tmp/nflx"
+
+ def serialise(tks: List[Token]) = {
+ val out = new ObjectOutputStream(new FileOutputStream(fname))
+ out.writeObject(tks)
+ out.close
+ }
+
+ def deserialise() : List[Token] = {
+ val in = new ObjectInputStream(new FileInputStream(fname))
+ val tks = in.readObject.asInstanceOf[List[Token]]
+ in.close
+ tks
+ }
+
+ serialise(tokenise(prog2))
+ println(deserialise())
+
+}
\ No newline at end of file