it.unich.scalafix.finite.HierarchicalOrderingSolver.scala Maven / Gradle / Ivy

Go to download
/**
 * Copyright 2015, 2016 Gianluca Amato 
 *
 * This file is part of ScalaFix. ScalaFix is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * ScalaFix is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of a MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * ScalaFix. If not, see .
 */

package it.unich.scalafix.finite

import it.unich.scalafix.*
import it.unich.scalafix.assignments.*

/** A solver whose strategy in based on a hierarchical ordering. */
object HierarchicalOrderingSolver:
  /**
   * Solve a finite equation system.
   *
   * @tparam U
   *   type of the unknowns for the equation system
   * @tparam V
   *   type of values of the equatiom system
   * @param eqs
   *   equation system to solve
   * @param start
   *   assignment to start the evaluation
   * @param ordering
   *   a hierarchical ordering which specifies priorities between unknowns
   *   (defaults to the hierarchical ordering induce by the depth-first ordering
   *   over `eqs`)
   * @param tracer
   *   a tracer to track the behaviour of the solver (defaults to the empty
   *   tracer)
   * @return
   *   the solution of the equation system
   */
  def apply[U, V](eqs: FiniteEquationSystem[U, V, ?])(
      start: Assignment[U, V],
      ordering: HierarchicalOrdering[U] = HierarchicalOrdering(DFOrdering(eqs)),
      tracer: FixpointSolverTracer[U, V] = FixpointSolverTracer.empty[U, V]
  ): MutableAssignment[U, V] =
    import HierarchicalOrdering.*

    val current = eqs.getMutableAssignment(start)
    tracer.initialized(current)
    var stack = List.empty[Int]
    var stackdirty = List.empty[Boolean]

    var dirty = false
    var i = 0
    val sequence = ordering.toSeqWithParenthesis

    while i < sequence.length do
      sequence(i) match
        case Left =>
          stack = (i + 1) +: stack
          stackdirty = dirty +: stackdirty
          dirty = false
          i += 1
        case Val(x) =>
          val newval = eqs.body(current)(x)
          tracer.evaluated(current, x, newval)
          if newval != current(x) then
            current(x) = newval
            dirty = true
          i += 1
        case Right =>
          if dirty then
            i = stack.head
            dirty = false
          else
            stack = stack.tail
            dirty = stackdirty.head
            stackdirty = stackdirty.tail
            i += 1
    tracer.completed(current)
    current