Init

cs420-acc/l3-warmup/compiler/src/l3/package.scala

@@ -0,0 +1,49 @@
+package object l3 {
+  type TerminalPhaseResult = Either[String, (Int, Option[String])]
+
+  type L3BlockTag = Int
+  type L3Char = Int
+
+  // A 32-bit integer (which could contain a pointer, a tagged value,
+  // or an untagged value).
+  type Bits32 = Int
+
+  val L3_INT_BITS = java.lang.Integer.SIZE - 1
+
+  // Bit twiddling
+  def bitsToIntMSBF(bits: Int*): Int =
+    bits.foldLeft(0) { (v, b) => (v << 1) | b }
+
+  def fitsInNSignedBits(bits: Int)(value: Int): Boolean = {
+    require(0 <= bits && bits < Integer.SIZE)
+    val value1 = value >> (bits - 1)
+    value1 == 0 || value1 == -1
+  }
+
+  def fitsInNUnsignedBits(bits: Int)(value: Int): Boolean = {
+    require(0 <= bits && bits < Integer.SIZE)
+    (value >>> bits) == 0
+  }
+
+  // Substitutions
+  type Subst[T] = Map[T, T]
+  def emptySubst[T]: Subst[T] =
+    Map.empty[T, T].withDefault(identity)
+  def subst[T](from: T, to: T): Subst[T] =
+    emptySubst[T] + (from -> to)
+  def subst[T](from: Seq[T], to: Seq[T]): Subst[T] =
+    emptySubst[T] ++ (from zip to)
+
+  // Fixed point computation
+  private def fixedPoint[T](start: T, maxIt: Option[Int])(f: T=>T): T = {
+    val approx = LazyList.iterate(start, maxIt getOrElse Integer.MAX_VALUE)(f)
+    val (improv, stable) = ((approx zip approx.tail) span (p => p._1 != p._2))
+    if (improv.isEmpty) stable.head._1 else improv.last._2
+  }
+
+  private[l3] def fixedPoint[T](start: T)(f: T=>T): T =
+    fixedPoint(start, None)(f)
+
+  private[l3] def fixedPoint[T](start: T, maxIt: Int)(f: T=>T): T =
+    fixedPoint(start, Some(maxIt))(f)
+}