diff -r 54a483a33763 -r 02ef5c3abc51 solution/cw3/parser.sc --- a/solution/cw3/parser.sc Fri Oct 28 09:08:13 2022 +0100 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,246 +0,0 @@ -// CW3 - -import $file.lexer -import lexer._ - - -case class ~[+A, +B](_1: A, _2: B) -type IsSeq[A] = A => Seq[_] - -abstract class Parser[I : IsSeq, T] { - def parse(ts: I): Set[(T, I)] - - def parse_all(ts: I) : Set[T] = - for ((head, tail) <- parse(ts); if tail.isEmpty) yield head -} - -class SeqParser[I : IsSeq, T, S](p: => Parser[I, T], q: => Parser[I, S]) extends Parser[I, ~[T, S]] { - def parse(sb: I) = - for ((head1, tail1) <- p.parse(sb); - (head2, tail2) <- q.parse(tail1)) yield (new ~(head1, head2), tail2) -} - -class AltParser[I : IsSeq, T](p: => Parser[I, T], q: => Parser[I, T]) extends Parser[I, T] { - def parse(sb: I) = p.parse(sb) ++ q.parse(sb) -} - -class FunParser[I : IsSeq, T, S](p: => Parser[I, T], f: T => S) extends Parser[I, S] { - def parse(sb: I) = - for ((head, tail) <- p.parse(sb)) yield (f(head), tail) -} - -// New parser that takes as input a list of tokens -case class TokenListParser(ts: List[Token]) extends Parser[List[Token], List[Token]] { - def parse(tsb: List[Token]) = { - val (prefix, suffix) = tsb.splitAt(ts.length) - if (prefix == ts) Set((prefix, suffix)) else Set() - } -} - -// Implicit definitions to go from a token -// or a list of tokens to a TokenListParser -implicit def token2parser(t: Token) = TokenListParser(List(t)) -implicit def tokenList2parser(ts: List[Token]) = TokenListParser(ts) - -implicit def ParserOps[I : IsSeq, T](p: Parser[I, T]) = new { - def || (q : => Parser[I, T]) = new AltParser[I, T](p, q) - def ==>[S] (f: => T => S) = new FunParser[I, T, S](p, f) - def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q) -} - -implicit def TokenOps(t: Token) = new { - def || (q : => Parser[List[Token], List[Token]]) = new AltParser[List[Token], List[Token]](List(t), q) - def || (qs : List[Token]) = new AltParser[List[Token], List[Token]](List(t), qs) - def ==>[S] (f: => List[Token] => S) = new FunParser[List[Token], List[Token], S](List(t), f) - def ~[S](q : => Parser[List[Token], S]) = - new SeqParser[List[Token], List[Token], S](List(t), q) - def ~ (qs : List[Token]) = - new SeqParser[List[Token], List[Token], List[Token]](List(t), qs) -} - -implicit def TokenListOps(ts: List[Token]) = new { - def || (q : => Parser[List[Token], List[Token]]) = new AltParser[List[Token], List[Token]](ts, q) - def || (qs : List[Token]) = new AltParser[List[Token], List[Token]](ts, qs) - def ==>[S] (f: => List[Token] => S) = new FunParser[List[Token], List[Token], S](ts, f) - def ~[S](q : => Parser[List[Token], S]) = - new SeqParser[List[Token], List[Token], S](ts, q) - def ~ (qs : List[Token]) = - new SeqParser[List[Token], List[Token], List[Token]](ts, qs) -} - -// Abstract Syntax Trees -abstract class Stmt -abstract class AExp -abstract class BExp - -type Block = List[Stmt] - -case object Skip extends Stmt -case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt -case class While(b: BExp, bl: Block) extends Stmt -case class Assign(s: String, a: AExp) extends Stmt -case class Read(s: String) extends Stmt -case class WriteId(s: String) extends Stmt // for printing values of variables -case class WriteString(s: String) extends Stmt // for printing words - -case class Var(s: String) extends AExp -case class Num(i: Int) extends AExp -case class Aop(o: String, a1: AExp, a2: AExp) extends AExp - -case object True extends BExp -case object False extends BExp -case class Bop(o: String, a1: AExp, a2: AExp) extends BExp -case class And(b1: BExp, b2: BExp) extends BExp -case class Or(b1: BExp, b2: BExp) extends BExp - -case class IdParser() extends Parser[List[Token], String] { - def parse(tsb: List[Token]) = tsb match { - case T_ID(id) :: rest => Set((id, rest)) - case _ => Set() - } -} - -case class NumParser() extends Parser[List[Token], Int] { - def parse(tsb: List[Token]) = tsb match { - case T_NUM(n) :: rest => Set((n, rest)) - case _ => Set() - } -} - -case class StringParser() extends Parser[List[Token], String] { - def parse(tsb: List[Token]) = tsb match { - case T_STRING(s) :: rest => Set((s, rest)) - case _ => Set() - } -} - -// WHILE Language Parsing -lazy val AExp: Parser[List[Token], AExp] = - (Te ~ T_OP("+") ~ AExp) ==> { case x ~ _ ~ z => Aop("+", x, z): AExp } || - (Te ~ T_OP("-") ~ AExp) ==> { case x ~ _ ~ z => Aop("-", x, z): AExp } || Te -lazy val Te: Parser[List[Token], AExp] = - (Fa ~ T_OP("*") ~ Te) ==> { case x ~ _ ~ z => Aop("*", x, z): AExp } || - (Fa ~ T_OP("/") ~ Te) ==> { case x ~ _ ~ z => Aop("/", x, z): AExp } || - (Fa ~ T_OP("%") ~ Te) ==> { case x ~ _ ~ z => Aop("%", x, z): AExp } || Fa -lazy val Fa: Parser[List[Token], AExp] = - (T_PAREN("(") ~ AExp ~ T_PAREN(")")) ==> { case _ ~ y ~ _ => y } || - IdParser() ==> Var || - NumParser() ==> Num - -lazy val BExp: Parser[List[Token], BExp] = - (AExp ~ T_OP("==") ~ AExp) ==> { case x ~ _ ~ z => Bop("==", x, z): BExp } || - (AExp ~ T_OP("!=") ~ AExp) ==> { case x ~ _ ~ z => Bop("!=", x, z): BExp } || - (AExp ~ T_OP("<") ~ AExp) ==> { case x ~ _ ~ z => Bop("<", x, z): BExp } || - (AExp ~ T_OP(">") ~ AExp) ==> { case x ~ _ ~ z => Bop(">", x, z): BExp } || - (T_PAREN("(") ~ BExp ~ T_PAREN(")") ~ T_OP("&&") ~ BExp) ==> { case _ ~ y ~ _ ~ _ ~ v => And(y, v): BExp } || - (T_PAREN("(") ~ BExp ~ T_PAREN(")") ~ T_OP("||") ~ BExp) ==> { case _ ~ y ~ _ ~ _ ~ v => Or(y, v): BExp } || - (T_KEYWORD("true") ==> (_ => True: BExp )) || - (T_KEYWORD("false") ==> (_ => False: BExp )) || - (T_PAREN("(") ~ BExp ~ T_PAREN(")")) ==> { case _ ~ x ~ _ => x } - -lazy val Stmt: Parser[List[Token], Stmt] = - T_KEYWORD("skip") ==> (_ => Skip: Stmt) || - (IdParser() ~ T_OP(":=") ~ AExp) ==> { case id ~ _ ~ z => Assign(id, z): Stmt } || - (T_KEYWORD("if") ~ BExp ~ T_KEYWORD("then") ~ Block ~ T_KEYWORD("else") ~ Block) ==> { case _ ~ y ~ _ ~ u ~ _ ~ w => If(y, u, w): Stmt } || - (T_KEYWORD("while") ~ BExp ~ T_KEYWORD("do") ~ Block) ==> { case _ ~ y ~ _ ~ w => While(y, w) : Stmt } || - (T_KEYWORD("read") ~ IdParser()) ==> { case _ ~ id => Read(id): Stmt} || - (T_KEYWORD("write") ~ IdParser()) ==> { case _ ~ id => WriteId(id): Stmt} || - (T_KEYWORD("write") ~ StringParser()) ==> { case _ ~ s => WriteString(s): Stmt} || - (T_KEYWORD("write") ~ T_PAREN("(") ~ IdParser() ~ T_PAREN(")")) ==> { case _ ~ _ ~ id ~ _ => WriteId(id): Stmt} || - (T_KEYWORD("write") ~ T_PAREN("(") ~ StringParser() ~ T_PAREN(")")) ==> { case _ ~ _ ~ s ~ _ => WriteString(s): Stmt} - -lazy val Stmts: Parser[List[Token], Block] = - (Stmt ~ T_SEMI ~ Stmts) ==> { case x ~ _ ~ z => x :: z : Block } || - (Stmt ==> (s => List(s) : Block)) - -lazy val Block: Parser[List[Token], Block] = - (T_PAREN("{") ~ Stmts ~ T_PAREN("}")) ==> { case x ~ y ~ z => y} || - (Stmt ==> (s => List(s))) - -// Testing with programs 2 & 3 - -println("Fibonacci") -println(Stmts.parse_all(tokenise(os.read(os.pwd / "fib.while")))) - -println("Loops") -println(Stmts.parse_all(tokenise(os.read(os.pwd / "loops.while")))) - -println("Collatz") -println(Stmts.parse_all(tokenise(os.read(os.pwd / "collatz2.while")))) - - -// Interpreter - -// Environment to store values of variables -type Env = Map[String, Int] - -def eval_aexp(a: AExp, env: Env) : Int = a match { - case Num(i) => i - case Var(s) => env(s) - case Aop("+", a1, a2) => eval_aexp(a1, env) + eval_aexp(a2, env) - case Aop("-", a1, a2) => eval_aexp(a1, env) - eval_aexp(a2, env) - case Aop("*", a1, a2) => eval_aexp(a1, env) * eval_aexp(a2, env) - case Aop("/", a1, a2) => eval_aexp(a1, env) / eval_aexp(a2, env) - case Aop("%", a1, a2) => eval_aexp(a1, env) % eval_aexp(a2, env) -} - -def eval_bexp(b: BExp, env: Env) : Boolean = b match { - case True => true - case False => false - case Bop("==", a1, a2) => eval_aexp(a1, env) == eval_aexp(a2, env) - case Bop("!=", a1, a2) => !(eval_aexp(a1, env) == eval_aexp(a2, env)) - case Bop(">", a1, a2) => eval_aexp(a1, env) > eval_aexp(a2, env) - case Bop("<", a1, a2) => eval_aexp(a1, env) < eval_aexp(a2, env) - case And(b1, b2) => eval_bexp(b1, env) && eval_bexp(b2, env) - case Or(b1, b2) => eval_bexp(b1, env) || eval_bexp(b2, env) -} - -// Import needed to take int as input from the user -import scala.io.StdIn.readInt - -def eval_stmt(s: Stmt, env: Env) : Env = s match { - case Skip => env - case Assign(x, a) => env + (x -> eval_aexp(a, env)) - case If(b, bl1, bl2) => if (eval_bexp(b, env)) eval_bl(bl1, env) else eval_bl(bl2, env) - case While(b, bl) => - if (eval_bexp(b, env)) eval_stmt(While(b, bl), eval_bl(bl, env)) - else env - - case WriteId(x) => { print(env(x)) ; env } - case WriteString(x) => { - print(x.replaceAll("\"", "").replaceAll("""\\n""", "\n")) ; - env - } - - case Read(x) => { - println("Enter an integer and press ENTER:") ; - val n = readInt() ; // Note: Does not work when using the REPL - eval_stmt(Assign(x, Num(n)), env) - } -} - -def eval_bl(bl: Block, env: Env) : Env = bl match { - case Nil => env - case s::bl => eval_bl(bl, eval_stmt(s, env)) -} - -def eval(bl: Block) : Env = eval_bl(bl, Map()) - -println("Primes eval") -println(tokenise(os.read(os.pwd / "primes.while"))) -println(eval(Stmts.parse_all(tokenise(os.read(os.pwd / "primes.while"))).head)) - -println("Factors eval") -println(eval(Stmts.parse_all(tokenise(os.read(os.pwd / "factors.while"))).head)) - -println("Collatz2 eval") -println(eval(Stmts.parse_all(tokenise(os.read(os.pwd / "collatz2.while"))).head)) - -/* -println("Loops eval") -val start = System.nanoTime() -println(eval(Stmts.parse_all(tokenise(os.read(os.pwd / "loops.while"))).head)) -val end = System.nanoTime() -println("Time taken in seconds: ") -println((end - start)/(1.0e9)) -*/