diff -r 47f86885d481 -r e85600529ca5 while1.scala --- a/while1.scala Sun Dec 23 00:38:56 2012 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,220 +0,0 @@ -// A parser and evaluator for the WHILE language -// -import matcher._ -import parser._ - - -// some regular expressions -val SYM = RANGE("ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz_") -val DIGIT = RANGE("0123456789") -val ID = SEQ(SYM, STAR(ALT(SYM, DIGIT))) -val NUM = PLUS(DIGIT) -val KEYWORD = ALTS("skip", "while", "do", "if", "then", "else", "true", "false", "write") -val SEMI: Rexp = ";" -val OP: Rexp = ALTS(":=", "=", "-", "+", "*", "!=", "<", ">") -val WHITESPACE = PLUS(RANGE(" \n")) -val RPAREN: Rexp = ")" -val LPAREN: Rexp = "(" -val BEGIN: Rexp = "{" -val END: Rexp = "}" -val COMMENT = SEQS("/*", NOT(SEQS(STAR(ALLC), "*/", STAR(ALLC))), "*/") - -// tokens for classifying the strings that have been recognised -abstract class Token -case object T_WHITESPACE extends Token -case object T_COMMENT extends Token -case object T_SEMI extends Token -case object T_LPAREN extends Token -case object T_RPAREN extends Token -case object T_BEGIN extends Token -case object T_END extends Token -case class T_ID(s: String) extends Token -case class T_OP(s: String) extends Token -case class T_NUM(s: String) extends Token -case class T_KWD(s: String) extends Token - -val lexing_rules: List[(Rexp, List[Char] => Token)] = - List((KEYWORD, (s) => T_KWD(s.mkString)), - (ID, (s) => T_ID(s.mkString)), - (OP, (s) => T_OP(s.mkString)), - (NUM, (s) => T_NUM(s.mkString)), - (SEMI, (s) => T_SEMI), - (LPAREN, (s) => T_LPAREN), - (RPAREN, (s) => T_RPAREN), - (BEGIN, (s) => T_BEGIN), - (END, (s) => T_END), - (WHITESPACE, (s) => T_WHITESPACE), - (COMMENT, (s) => T_COMMENT)) - -// the tokenizer -val Tok = Tokenizer(lexing_rules, List(T_WHITESPACE, T_COMMENT)) - -// the 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 Write(s: String) extends Stmt - -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 - -// atomic parsers -case class TokParser(tok: Token) extends Parser[List[Token], Token] { - def parse(ts: List[Token]) = ts match { - case t::ts if (t == tok) => Set((t, ts)) - case _ => Set () - } -} -implicit def token2tparser(t: Token) = TokParser(t) - -case object NumParser extends Parser[List[Token], Int] { - def parse(ts: List[Token]) = ts match { - case T_NUM(s)::ts => Set((s.toInt, ts)) - case _ => Set () - } -} - -case object IdParser extends Parser[List[Token], String] { - def parse(ts: List[Token]) = ts match { - case T_ID(s)::ts => Set((s, ts)) - case _ => Set () - } -} - - -// arithmetic expressions -lazy val AExp: Parser[List[Token], AExp] = - (T ~ T_OP("+") ~ AExp) ==> { case ((x, y), z) => Aop("+", x, z): AExp } || - (T ~ T_OP("-") ~ AExp) ==> { case ((x, y), z) => Aop("-", x, z): AExp } || T -lazy val T: Parser[List[Token], AExp] = - (F ~ T_OP("*") ~ T) ==> { case ((x, y), z) => Aop("*", x, z): AExp } || F -lazy val F: Parser[List[Token], AExp] = - (T_LPAREN ~> AExp <~ T_RPAREN) || - IdParser ==> Var || - NumParser ==> Num - -// boolean expressions -lazy val BExp: Parser[List[Token], BExp] = - (T_KWD("true") ==> ((_) => True: BExp)) || - (T_KWD("false") ==> ((_) => False: BExp)) || - (T_LPAREN ~> BExp <~ T_RPAREN) || - (AExp ~ T_OP("=") ~ AExp) ==> { case ((x, y), z) => Bop("=", x, z): BExp } || - (AExp ~ T_OP("!=") ~ AExp) ==> { case ((x, y), z) => Bop("!=", x, z): BExp } || - (AExp ~ T_OP("<") ~ AExp) ==> { case ((x, y), z) => Bop("<", x, z): BExp } || - (AExp ~ T_OP(">") ~ AExp) ==> { case ((x, y), z) => Bop("<", z, x): BExp } - -lazy val Stmt: Parser[List[Token], Stmt] = - (T_KWD("skip") ==> ((_) => Skip: Stmt)) || - (IdParser ~ T_OP(":=") ~ AExp) ==> { case ((x, y), z) => Assign(x, z): Stmt } || - (T_KWD("if") ~ BExp ~ T_KWD("then") ~ Block ~ T_KWD("else") ~ Block) ==> - { case (((((x,y),z),u),v),w) => If(y, u, w): Stmt } || - (T_KWD("while") ~ BExp ~ T_KWD("do") ~ Block) ==> { case (((x, y), z), w) => While(y, w) } || - (T_KWD("write") ~ IdParser) ==> { case (x, y) => Write(y) } - -lazy val Stmts: Parser[List[Token], Block] = - (Stmt ~ T_SEMI ~ Stmts) ==> { case ((x, y), z) => x :: z : Block } || - (Stmt ==> ((s) => List(s) : Block)) - -lazy val Block: Parser[List[Token], Block] = - (T_BEGIN ~> Stmts <~ T_END) || - (Stmt ==> ((s) => List(s))) - -// interpreter -type Env = Map[String, Int] - -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) -} - -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) -} - -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 Write(x) => { println(env(x)); 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_prog(name: String) : Env = { - val tks = Tok.fromFile(name) - val ast = Stmts.parse_single(tks) - eval_bl(ast, Map.empty) -} - - -//examples - -//eval_prog("loops.while") -eval_prog("fib.while") - - -def time_needed[T](i: Int, code: => T) = { - val start = System.nanoTime() - for (j <- 1 to i) code - val end = System.nanoTime() - (end - start)/(i * 1.0e9) -} - - -val test_prog = """ -start := XXX; -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 -} -""" - - - -def eval_test(n: Int) : Unit = { - val tks = Tok.fromString(test_prog.replaceAllLiterally("XXX", n.toString)) - val ast = Stmts.parse_single(tks) - println(n + " " + time_needed(2, eval_bl(ast, Map.empty))) -} - -List(1, 200, 400, 600, 800, 1000, 1200, 1400, 1600).map(eval_test(_)) - - - - - - -