--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/funt.scala Sat Jul 04 22:12:18 2020 +0100
@@ -0,0 +1,543 @@
+// A Small Compiler for a Simple Functional Language
+// (includes a lexer and a parser)
+
+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.%
+
+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" | "T" | "_"
+val DIGIT = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
+val ID = SYM ~ (SYM | DIGIT).%
+val NUM = PLUS(DIGIT)
+val KEYWORD : Rexp = "if" | "then" | "else" | "write" | "def"
+val SEMI: Rexp = ";"
+val OP: Rexp = "=" | "==" | "-" | "+" | "*" | "!=" | "<" | ">" | "<=" | ">=" | "%" | "/"
+val WHITESPACE = PLUS(" " | "\n" | "\t")
+val RPAREN: Rexp = ")"
+val LPAREN: Rexp = "("
+val COMMA: Rexp = ","
+val ALL = SYM | DIGIT | OP | " " | ":" | ";" | "\"" | "=" | "," | "(" | ")"
+val ALL2 = ALL | "\n"
+val COMMENT = ("/*" ~ ALL2.% ~ "*/") | ("//" ~ ALL.% ~ "\n")
+
+
+val WHILE_REGS = (("k" $ KEYWORD) |
+ ("i" $ ID) |
+ ("o" $ OP) |
+ ("n" $ NUM) |
+ ("s" $ SEMI) |
+ ("c" $ COMMA) |
+ ("pl" $ LPAREN) |
+ ("pr" $ RPAREN) |
+ ("w" $ (WHITESPACE | COMMENT))).%
+
+
+
+// The tokens for the Fun language
+
+abstract class Token
+case object T_SEMI extends Token
+case object T_COMMA 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
+
+val token : PartialFunction[(String, String), Token] = {
+ case ("k", s) => T_KWD(s)
+ case ("i", s) => T_ID(s)
+ case ("o", s) => T_OP(s)
+ case ("n", s) => T_NUM(s.toInt)
+ case ("s", _) => T_SEMI
+ case ("c", _) => T_COMMA
+ case ("pl", _) => T_LPAREN
+ case ("pr", _) => T_RPAREN
+}
+
+
+def tokenise(s: String) : List[Token] =
+ lexing_simp(WHILE_REGS, s).collect(token)
+
+
+
+// Parser combinators
+abstract class Parser[I, T](implicit ev: I => Seq[_]) {
+ def parse(ts: I): Set[(T, I)]
+
+ def parse_all(ts: I) : Set[T] =
+ for ((head, tail) <- parse(ts); if (tail.isEmpty)) yield head
+
+ def parse_single(ts: I) : T = parse_all(ts).toList match {
+ case List(t) => t
+ case _ => { println ("Parse Error\n") ; sys.exit(-1) }
+ }
+}
+
+// convenience for matching later on
+case class ~[+A, +B](_1: A, _2: B)
+
+
+class SeqParser[I, T, S](p: => Parser[I, T],
+ q: => Parser[I, S])(implicit ev: I => Seq[_]) 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, T](p: => Parser[I, T],
+ q: => Parser[I, T])(implicit ev: I => Seq[_]) extends Parser[I, T] {
+ def parse(sb: I) = p.parse(sb) ++ q.parse(sb)
+}
+
+class FunParser[I, T, S](p: => Parser[I, T],
+ f: T => S)(implicit ev: I => Seq[_]) extends Parser[I, S] {
+ def parse(sb: I) =
+ for ((head, tail) <- p.parse(sb)) yield (f(head), tail)
+}
+
+implicit def ParserOps[I, T](p: Parser[I, T])(implicit ev: I => Seq[_]) = 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)
+}
+
+def ListParser[I, T, S](p: => Parser[I, T],
+ q: => Parser[I, S])(implicit ev: I => Seq[_]): Parser[I, List[T]] = {
+ (p ~ q ~ ListParser(p, q)) ==> { case x ~ _ ~ z => x :: z : List[T] } ||
+ (p ==> ((s) => List(s)))
+}
+
+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)
+
+implicit def TokOps(t: Token) = new {
+ def || (q : => Parser[List[Token], Token]) = new AltParser[List[Token], Token](t, q)
+ def ==>[S] (f: => Token => S) = new FunParser[List[Token], Token, S](t, f)
+ def ~[S](q : => Parser[List[Token], S]) = new SeqParser[List[Token], Token, S](t, q)
+}
+
+case object NumParser extends Parser[List[Token], Int] {
+ def parse(ts: List[Token]) = ts match {
+ case T_NUM(n)::ts => Set((n, 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 ()
+ }
+}
+
+
+
+// Abstract syntax trees for Fun
+abstract class Exp
+abstract class BExp
+abstract class Decl
+
+case class Def(name: String, args: List[String], body: Exp) extends Decl
+case class Main(e: Exp) extends Decl
+
+case class Call(name: String, args: List[Exp]) extends Exp
+case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
+case class Write(e: Exp) extends Exp
+case class Var(s: String) extends Exp
+case class Num(i: Int) extends Exp
+case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
+case class Sequence(e1: Exp, e2: Exp) extends Exp
+case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
+
+
+
+// Grammar Rules for Fun
+
+// arithmetic expressions
+lazy val Exp: Parser[List[Token], Exp] =
+ (T_KWD("if") ~ BExp ~ T_KWD("then") ~ Exp ~ T_KWD("else") ~ Exp) ==>
+ { case _ ~ y ~ _ ~ u ~ _ ~ w => If(y, u, w): Exp } ||
+ (M ~ T_SEMI ~ Exp) ==> { case x ~ _ ~ z => Sequence(x, z): Exp } || M
+lazy val M: Parser[List[Token], Exp] =
+ (T_KWD("write") ~ L) ==> { case _ ~ y => Write(y): Exp } || L
+lazy val L: Parser[List[Token], Exp] =
+ (T ~ T_OP("+") ~ Exp) ==> { case x ~ _ ~ z => Aop("+", x, z): Exp } ||
+ (T ~ T_OP("-") ~ Exp) ==> { case x ~ _ ~ z => Aop("-", x, z): Exp } || T
+lazy val T: Parser[List[Token], Exp] =
+ (F ~ T_OP("*") ~ T) ==> { case x ~ _ ~ z => Aop("*", x, z): Exp } ||
+ (F ~ T_OP("/") ~ T) ==> { case x ~ _ ~ z => Aop("/", x, z): Exp } ||
+ (F ~ T_OP("%") ~ T) ==> { case x ~ _ ~ z => Aop("%", x, z): Exp } || F
+lazy val F: Parser[List[Token], Exp] =
+ (IdParser ~ T_LPAREN ~ ListParser(Exp, T_COMMA) ~ T_RPAREN) ==>
+ { case x ~ _ ~ z ~ _ => Call(x, z): Exp } ||
+ (T_LPAREN ~ Exp ~ T_RPAREN) ==> { case _ ~ y ~ _ => y: Exp } ||
+ IdParser ==> { case x => Var(x): Exp } ||
+ NumParser ==> { case x => Num(x): Exp }
+
+// boolean expressions
+lazy val BExp: Parser[List[Token], BExp] =
+ (Exp ~ T_OP("==") ~ Exp) ==> { case x ~ _ ~ z => Bop("==", x, z): BExp } ||
+ (Exp ~ T_OP("!=") ~ Exp) ==> { case x ~ _ ~ z => Bop("!=", x, z): BExp } ||
+ (Exp ~ T_OP("<") ~ Exp) ==> { case x ~ _ ~ z => Bop("<", x, z): BExp } ||
+ (Exp ~ T_OP(">") ~ Exp) ==> { case x ~ _ ~ z => Bop("<", z, x): BExp } ||
+ (Exp ~ T_OP("<=") ~ Exp) ==> { case x ~ _ ~ z => Bop("<=", x, z): BExp } ||
+ (Exp ~ T_OP("=>") ~ Exp) ==> { case x ~ _ ~ z => Bop("<=", z, x): BExp }
+
+lazy val Defn: Parser[List[Token], Decl] =
+ (T_KWD("def") ~ IdParser ~ T_LPAREN ~ ListParser(IdParser, T_COMMA) ~ T_RPAREN ~ T_OP("=") ~ Exp) ==>
+ { case x ~ y ~ z ~ w ~ u ~ v ~ r => Def(y, w, r): Decl }
+
+lazy val Prog: Parser[List[Token], List[Decl]] =
+ (Defn ~ T_SEMI ~ Prog) ==> { case x ~ _ ~ z => x :: z : List[Decl] } ||
+ (Exp ==> ((s) => List(Main(s)) : List[Decl]))
+
+
+// compiler - built-in functions
+// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html
+//
+
+val library = """
+.class public XXX.XXX
+.super java/lang/Object
+
+.method public static write(I)V
+ .limit locals 1
+ .limit stack 2
+ getstatic java/lang/System/out Ljava/io/PrintStream;
+ iload 0
+ invokevirtual java/io/PrintStream/println(I)V
+ return
+.end method
+
+"""
+
+// calculating the maximal needed stack size
+def max_stack_exp(e: Exp): Int = e match {
+ case Call(_, args) => args.map(max_stack_exp).sum
+ case If(a, e1, e2) => max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max)
+ case Write(e) => max_stack_exp(e) + 1
+ case Var(_) => 1
+ case Num(_) => 1
+ case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+ case Sequence(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max
+}
+def max_stack_bexp(e: BExp): Int = e match {
+ case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+}
+
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+ counter += 1
+ x ++ "_" ++ counter.toString()
+}
+
+// convenient string interpolations
+// for instructions, labels and methods
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+implicit def sring_inters(sc: StringContext) = new {
+ def i(args: Any*): String = " " ++ sc.s(args:_*) ++ "\n"
+ def l(args: Any*): String = sc.s(args:_*) ++ ":\n"
+ def m(args: Any*): String = sc.s(args:_*) ++ "\n"
+}
+
+
+type Env = Map[String, Int]
+
+
+def compile_expT(a: Exp, env : Env, name: String) : String = a match {
+ case Num(i) => i"ldc $i"
+ case Var(s) => i"iload ${env(s)}"
+ case Aop("+", a1, a2) => compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"iadd"
+ case Aop("-", a1, a2) => compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"isub"
+ case Aop("*", a1, a2) => compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"imul"
+ case Aop("/", a1, a2) => compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"idiv"
+ case Aop("%", a1, a2) => compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"irem"
+ case If(b, a1, a2) => {
+ val if_else = Fresh("If_else")
+ val if_end = Fresh("If_end")
+ compile_bexpT(b, env, if_else) ++
+ compile_expT(a1, env, name) ++
+ i"goto $if_end" ++
+ l"$if_else" ++
+ compile_expT(a2, env, name) ++
+ l"$if_end"
+ }
+ case Call(n, args) => if (name == n) {
+ val stores = args.zipWithIndex.map { case (x, y) => i"istore $y" }
+ args.map(a => compile_expT(a, env, "")).mkString ++
+ stores.reverse.mkString ++
+ i"goto ${n}_Start"
+ } else {
+ val is = "I" * args.length
+ args.map(a => compile_expT(a, env, "")).mkString ++
+ i"invokestatic XXX/XXX/${n}(${is})I"
+ }
+ case Sequence(a1, a2) => {
+ compile_expT(a1, env, "") ++ i"pop" ++ compile_expT(a2, env, name)
+ }
+ case Write(a1) => {
+ compile_expT(a1, env, "") ++
+ i"dup" ++
+ i"invokestatic XXX/XXX/write(I)V"
+ }
+}
+
+def compile_bexpT(b: BExp, env : Env, jmp: String) : String = b match {
+ case Bop("==", a1, a2) =>
+ compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"if_icmpne $jmp"
+ case Bop("!=", a1, a2) =>
+ compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"if_icmpeq $jmp"
+ case Bop("<", a1, a2) =>
+ compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"if_icmpge $jmp"
+ case Bop("<=", a1, a2) =>
+ compile_expT(a1, env, "") ++ compile_expT(a2, env, "") ++ i"if_icmpgt $jmp"
+}
+
+
+def compile_decl(d: Decl) : String = d match {
+ case Def(name, args, a) => {
+ val env = args.zipWithIndex.toMap
+ val is = "I" * args.length
+ m".method public static $name($is)I" ++
+ m".limit locals ${args.length}" ++
+ m".limit stack ${1 + max_stack_exp(a)}" ++
+ l"${name}_Start" ++
+ compile_expT(a, env, name) ++
+ i"ireturn" ++
+ m".end method\n"
+ }
+ case Main(a) => {
+ m".method public static main([Ljava/lang/String;)V" ++
+ m".limit locals 200" ++
+ m".limit stack 200" ++
+ compile_expT(a, Map(), "") ++
+ i"invokestatic XXX/XXX/write(I)V" ++
+ i"return\n" ++
+ m".end method\n"
+ }
+}
+
+// main compiler functions
+
+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)
+}
+
+def compile(class_name: String, input: String) : String = {
+ val tks = tokenise(input)
+ val ast = Prog.parse_single(tks)
+ val instructions = ast.map(compile_decl).mkString
+ (library + instructions).replaceAllLiterally("XXX", class_name)
+}
+
+def compile_file(class_name: String) = {
+ val input = io.Source.fromFile(s"${class_name}.fun").mkString
+ val output = compile(class_name, input)
+ scala.tools.nsc.io.File(s"${class_name}.j").writeAll(output)
+}
+
+import scala.sys.process._
+
+def compile_run(class_name: String) : Unit = {
+ compile_file(class_name)
+ (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
+ println("Time: " + time_needed(2, (s"java ${class_name}/${class_name}").!))
+}
+
+
+//examples
+compile_run("defs")
+compile_run("fact")