254 lines
9.4 KiB
Scala
254 lines
9.4 KiB
Scala
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package l3
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import fastparse._
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import NominalCL3TreeModule._
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/**
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* Parsing (including lexical analysis) for the L₃ language.
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*
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* @author Michel Schinz <Michel.Schinz@epfl.ch>
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*/
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object L3Parser {
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def parse(programText: String,
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indexToPosition: Int => Position): Either[String, Tree] = {
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val parser = new S(indexToPosition)
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fastparse.parse(programText, parser.program(_)) match {
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case Parsed.Success(program, _) =>
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Right(program)
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case Parsed.Failure(lp, index, _) =>
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Left(s"${indexToPosition(index)}: parse error (expected: $lp)")
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}
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}
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// Lexical analysis (for which whitespace is significant)
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private class L(indexToPosition: Int => Position) {
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import NoWhitespace._
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private implicit val indexToPositionView = indexToPosition
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// Literals
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private def sign[_: P] = P(CharIn("+\\-"))
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private def prefix2[_: P] = IgnoreCase("#b")
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private def prefix16[_: P] = IgnoreCase("#x")
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private def digit2[_: P] = CharIn("0-1")
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private def digit10[_: P] = CharIn("0-9")
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private def digit16[_: P] = CharIn("0-9a-fA-F")
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private def unicodeChar[_: P] = P(
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CharPred(!Character.isHighSurrogate(_))
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| (CharPred(Character.isHighSurrogate)
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~ CharPred(Character.isLowSurrogate)))
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private def integer2[_: P] = P(
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(prefix2 ~/ digit2.rep(1).!)
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.map { Integer.parseInt(_, 2) }
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.filter { L3Int.canConvertFromIntUnsigned(_) }
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.map { L3Int.ofIntUnsigned(_) })
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private def integer16[_: P] = P(
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(prefix16 ~/ digit16.rep(1).!)
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.map { Integer.parseInt(_, 16) }
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.filter { L3Int.canConvertFromIntUnsigned(_) }
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.map { L3Int.ofIntUnsigned(_) })
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private def integer10[_: P] = P(
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(sign.? ~ digit10 ~/ digit10.rep).!
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.map { Integer.parseInt(_, 10) }
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.filter { L3Int.canConvertFromInt(_) })
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.map { L3Int(_) }
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private def integer[_: P] = P(
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(Index ~ (integer2 | integer10 | integer16))
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.map { case (i, v) => Lit(IntLit(v))(i) })
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private def string[_: P] = P(
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(Index ~ "\"" ~/ CharPred(c => c != '\n' && c != '"').rep.! ~ "\"")
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.map { case (i, s) => sStringLit(s)(i) })
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private def char[_: P] = P(
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(Index ~ "'" ~/ unicodeChar.! ~ "'")
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.map { case (i, c) => Lit(CharLit(c.codePointAt(0)))(i) })
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private def bool[_: P] = P(
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(Index ~ StringIn("#t", "#f").!)
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.map { case (i, v) => Lit(BooleanLit(v == "#t"))(i) })
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private def unit[_: P] = P(
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(Index ~ "#u")
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.map { case i => Lit(UnitLit)(i) })
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def literal[_: P] = P(integer | string | char | bool | unit)
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// Identifiers
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private def identStart[_: P] = P(CharIn("|!%&*+\\-./:<=>?^_~a-zA-Z"))
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private def identCont[_: P] = P(identStart | digit10)
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private def identSuffix[_: P] = P("@" ~ digit10.rep(1))
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def identStr[_: P] = P(
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(identStart ~/ identCont.rep ~/ identSuffix.?).!)
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def identifier[_: P] = P(
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(Index ~ identStr).map { case (i, n) => Ident(n)(i) })
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// Keywords
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def kDef[_: P] = P("def" ~ !identCont)
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def kDefrec[_: P] = P("defrec" ~ !identCont)
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def kFun[_: P] = P("fun" ~ !identCont)
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def kLet[_: P] = P("let" ~ !identCont)
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def kLet_*[_: P] = P("let*" ~ !identCont)
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def kLetrec[_: P] = P("letrec" ~ !identCont)
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def kRec[_: P] = P("rec" ~ !identCont)
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def kBegin[_: P] = P("begin" ~ !identCont)
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def kCond[_: P] = P("cond" ~ !identCont)
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def kIf[_: P] = P("if" ~ !identCont)
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def kAnd[_: P] = P("and" ~ !identCont)
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def kOr[_: P] = P("or" ~ !identCont)
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def kNot[_: P] = P("not" ~ !identCont)
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def kHalt[_: P] = P("halt" ~ !identCont)
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def kPrim[_: P] = P("@")
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}
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// Syntactic analysis (for which whitespace and comments are ignored)
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private class S(indexToPosition: Int => Position) {
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val lexer = new L(indexToPosition)
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import lexer._
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private implicit val whitespace = { implicit ctx: ParsingRun[_] =>
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import NoWhitespace._
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(CharIn(" \t\n\r")
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}
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private implicit val indexToPositionView = indexToPosition
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def program[_: P]: P[Tree] =
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P("" ~ topExpr ~ End) // The initial "" allows leading whitespace
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private def topExpr[_: P]: P[Tree] = P(defP | defrecP | exprP)
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private def defP[_: P] = P(
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(iPar(kDef ~ identStr ~ expr) ~ topExpr)
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.map { case (i, (n, v), p) => Let(Seq((n, v)), p)(i) })
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private def defrecP[_: P] = P(
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(iPar(kDefrec ~ identStr ~ anonFun) ~ topExpr)
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.map { case (i, (n, (a, b)), p) =>
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LetRec(Seq(Fun(n, a, b)(i)), p)(i) })
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private def exprP[_: P] = P(
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(ix(expr ~ topExpr.?))
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.map { case (i, (e, p)) => sBegin(e +: p.toSeq)(i) })
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private def expr[_: P]: P[Tree] = P(
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fun | let | let_* | letrec | rec | begin | cond | if_ | and | or | not
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| halt | app | prim | literal | identifier)
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private def exprs[_: P] = expr.rep
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private def iExprs[_: P] = ix(exprs)
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private def exprs1[_: P] = expr.rep(1)
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private def iExprs1[_: P] = ix(exprs1)
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private def anonFun[_: P] = P(
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par("fun" ~ par(identStr.rep) ~ iExprs1)
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.map { case (a, (i, e)) => (a, sBegin(e)(i)) })
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private def funDef[_: P] = P(
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iPar(identStr ~ anonFun)
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.map { case (i, (n, (a, e))) => Fun(n, a, e)(i) })
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private def binding[_: P] = P(
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par(identStr ~ expr)
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.map { case (i, e) => (i, e) })
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private def bindings[_: P] = P(
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par(binding.rep))
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private def fun[_: P] = P(
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ix(anonFun)
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.map { case (i, (a, e)) => sFun(a, e)(i) })
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private def let[_: P] = P(
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iPar(kLet ~/ bindings ~ iExprs1)
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.map { case (i1, (b, (i2, e))) => Let(b, sBegin(e)(i2))(i1) })
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private def let_*[_: P] = P(
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iPar(kLet_* ~/ bindings ~ iExprs1)
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.map { case (i1, (b, (i2, e))) => sLet_*(b, sBegin(e)(i2))(i1) })
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private def letrec[_: P]= P(
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iPar(kLetrec ~/ par(funDef.rep) ~ iExprs1)
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.map { case (i1, (f, (i2, e))) => LetRec(f, sBegin(e)(i2))(i1) })
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private def rec[_: P] = P(
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iPar(kRec ~/ identStr ~ bindings ~ iExprs1)
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.map { case (i1, (n, b, (i2, e))) => sRec(n, b, sBegin(e)(i2))(i1) })
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private def begin[_: P] = P(
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iPar(kBegin ~/ exprs1)
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.map { case (i, e) => sBegin(e)(i) })
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private def cond[_: P] = P(
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iPar(kCond ~/ par(expr ~ exprs).rep(1))
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.map { case (i, a) => sCond(a)(i) })
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private def if_[_: P] = P(
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iPar(kIf ~ expr ~ expr ~ expr.?)
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.map { case (i, (c, t, f)) =>
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If(c, t, f.getOrElse(Lit(UnitLit)(i)))(i) })
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private def and[_: P] = P(
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iPar(kAnd ~/ expr.rep(2))
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.map { case (i, es) => sAnd(es)(i) })
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private def or[_: P] = P(
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iPar(kOr ~/ expr.rep(2))
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.map { case (i, es) => sOr(es)(i) })
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private def not[_: P] = P(
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iPar(kNot ~/ expr)
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.map { case (i, e) => sNot(e)(i) })
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private def app[_: P] = P(
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iPar(expr ~ exprs)
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.map { case (i, (e, es)) => App(e, es)(i) })
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private def prim[_: P] = P(
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iPar(kPrim ~/ identStr ~ exprs)
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.map { case (i, (p, es)) => Prim(p, es)(i) })
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private def halt[_: P] = P(
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iPar(kHalt ~/ expr)
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.map { case (i, e) => Halt(e)(i) })
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private def par[T, _: P](b: =>P[T]): P[T] = P("(" ~ b ~ ")")
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private def ix[T, _: P](b: =>P[T]): P[(Int, T)] = Index ~ b
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private def iPar[T, _: P](b: =>P[T]): P[(Int, T)] = ix(par(b))
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}
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// Syntactic sugar translation.
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private var freshCounter = 0
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private def freshName(prefix: String): String = {
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freshCounter += 1
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prefix + "$" + freshCounter
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}
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private def sFun(args: Seq[String], body: Tree)
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(implicit p: Position): Tree = {
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val fn = freshName("sfun")
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LetRec(Seq(Fun(fn, args, body)), Ident(fn))
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}
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private def sLet_*(bdgs: Seq[(String,Tree)], body: Tree)(implicit p: Position): Tree =
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bdgs.foldRight(body)((b,t)=>Let(Seq(b),t))
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private def sBegin(exprs: Seq[Tree])(implicit p: Position): Tree =
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exprs.reduceRight((e1,e2)=>Let(Seq((freshName("sbegin"), e1)),e2))
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private def sRec(name: String, bdgs: Seq[(String, Tree)], body: Tree)(implicit p: Position) =
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LetRec(Seq(Fun(name, bdgs.map(_._1), body)), App(Ident(name), bdgs.map(_._2)))
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private def sAnd(es: Seq[Tree])(implicit p: Position): Tree =
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es.reduceRight(If(_,_,Lit(BooleanLit(false))))
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private def sOr(es: Seq[Tree])(implicit p: Position): Tree =
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es.reduceRight((e, r) =>{
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val fn = freshName("sor")
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Let(Seq((fn, e)), If(Ident(fn), Ident(fn), r))
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})
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private def sNot(e: Tree)(implicit p: Position): Tree =
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If(e, Lit(BooleanLit(false)), Lit(BooleanLit(true)))
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private def sCond(clses: Seq[(Tree, Seq[Tree])])(implicit p: Position): Tree =
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clses.foldRight(Lit(UnitLit): Tree){ case ((c, t), e) =>
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If(c, sBegin(t), e)
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}
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private def sStringLit(s: String)(implicit p: Position): Tree = {
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val b = freshName("string")
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val cs = codePoints(s)
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Let(Seq((b, Prim("block-alloc-"+ BlockTag.String.id,
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Seq(Lit(IntLit(L3Int(cs.length))))))),
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sBegin((cs.zipWithIndex map {case (c, i) =>
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Prim("block-set!",
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Seq(Ident(b), Lit(IntLit(L3Int(i))), Lit(CharLit(c)))) })
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:+ Ident(b)))
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}
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private def codePoints(chars: Seq[Char]): Seq[L3Char] = chars match {
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case Seq(h, l, r @ _*) if (Character.isSurrogatePair(h, l)) =>
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Character.toCodePoint(h, l) +: codePoints(r)
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case Seq(c, r @ _*) =>
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c.toInt +: codePoints(r)
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case Seq() =>
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Seq()
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}
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}
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