sclass BodyOfEvidence<Src> {
  // values are: WithProbability(strengthOfEvidence, probabilityOfTheory)
  // will only hold one piece of evidence per src object
  Map<Src, WithProbability<Double>> examples = syncMap();
  double strengthSum, probabilitySum;
  
  O mutex() { ret examples; }
  
  double currentProbabilityGuess() {
    synchronized(mutex()) {
      ret doubleRatio(probabilitySum, strengthSum);
    }
  }
  
  S renderProbabilityGuess() {
    ret "Current probability guess (evidence count " + n2(l(examples)) + "): " + formatDouble3X(currentProbabilityGuess()) + " with strength " + formatDouble3(strengthSum);
  }
  
  bool hasEvidenceFromSource(Src src) { ret examples.containsKey(src); }
  
  bool addEvidence(Src src, double probabilityOfTheory, double strengthOfEvidence) {
    synchronized(mutex()) {
      if (hasEvidenceFromSource(src)) false;
      examples.put(src, withProbability(strengthOfEvidence, probabilityOfTheory));
      probabilitySum += probabilityOfTheory*strengthOfEvidence;
      strengthSum += strengthOfEvidence;
      true;
    }
  }
  
  S toStringWithEvidence() {
    ret toString() + "\n\n"
      + pnlToString("EVIDENCE", multiMapToPairs(examples));
  }
}