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/* NSC -- new Scala compiler
* Copyright 2005-2010 LAMP/EPFL
* @author Martin Odersky
*/
// $Id$
package scala.tools.nsc
package backend.icode.analysis
/** A complete lattice.
*/
trait CompleteLattice {
type Elem <: AnyRef
/** Hold together local variable and stack state. The
* equals method uses reference equality for top and bottom,
* and structural equality for other values.
*/
case class IState[V, S](val vars: V, val stack: S) {
override def equals(other: Any): Boolean = other match {
case that: IState[_, _] =>
if ((this eq bottom) || (that eq bottom)) this eq that
else if ((this eq top) || (that eq top)) this eq that
else (stack == that.stack && vars == that.vars)
case _ => false
}
}
/** Return the least upper bound of <code>a</code> and <code>b</code> */
def lub2(exceptional: Boolean)(a: Elem, b: Elem): Elem
/** Return the top element. */
def top: Elem
/** Return the bottom element. */
def bottom: Elem
/** Compute the least upper bound of a list of elements. */
def lub(xs: List[Elem], exceptional: Boolean): Elem = try {
if (xs == Nil) bottom else xs reduceLeft lub2(exceptional)
} catch {
case e: LubException =>
Console.println("Lub on blocks: " + xs)
throw e
}
}
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