stsys/lib/cpmgr.js

String rewriting system (semi-Thue system)

class Bucket
{
  constructor()
  {
    this.first = null;
    this.last = null;
  }

  getNext()
  {
    if (!this.first)
      return;
    const next = this.first;
    this.first = this.first.next;
    return next;
  }

  add(cp)
  {
    if (!this.first)
      this.first = this.last = cp;
    else
    {
      this.last.next = cp;
      this.last = cp;
    }
  }

  getSize()
  {
    let n = 0, cp = this.first;
    while (cp)
    {
      cp = cp.next;
      n++;
    }
    return n;
  }
}

class CpManager
{
  constructor()
  {
    this.currentBucketIndex = -1;
    this.cpBuckets = [];
  }

  getNext()
  {
    if (!this.updateCurrentBucketIndex())
      return;
    const bucket = this.cpBuckets[this.currentBucketIndex];
    const cp = bucket.getNext();
    if (!bucket.first)
      this.currentBucketIndex = -1;
    return cp;
  }

  hasNext()
  {
    return this.updateCurrentBucketIndex();
  }

  updateCurrentBucketIndex()
  {
    if (this.currentBucketIndex >= 0)
      return true;
    for (let i in this.cpBuckets)
    {
      if (this.cpBuckets[i].first)
      {
        this.currentBucketIndex = i;
        return true;
      }
    }
    return false;
  }

  addCp(cp)
  {
    const w = cp.getWeight();
    let bucket = this.cpBuckets[w];
    if (this.currentBucketIndex < 0 || w < this.currentBucketIndex)
      this.currentBucketIndex = w;
    if (!bucket)
      bucket = this.cpBuckets[w] = new Bucket();
    bucket.add(cp);
  }

  toString()
  {
    const sb = ['index: ' + this.currentBucketIndex];
    for (let w in this.cpBuckets)
    {
      sb.push(w + ': ' + this.cpBuckets[w].getSize());
    }
    return sb.join('\n');
  }

  totalCpCount()
  {
    let count = 0;
    for (let w in this.cpBuckets)
    {
      count += this.cpBuckets[w].getSize();
    }
    return count;
  }
}

module.exports.createCpManager = function()
{
  return new CpManager();
};