sclass AI_CalculationBot > AttractorBot {
  bool greet = true;
  
  run {
    if (greet) say("I can calculate things for you");
  }
  
  // CONFIG
  
  class CalcAttractor > Attractor {
    S op;
    L<Number> arguments;
    
    public bool matches(S s) {
      LS l = regexpFirstGroups("(\\d+)\\s*[x*]\\s*(\\d+)", s);
      if (l(l) == 2)
        ret setOp(f mul, l);

      l = splitAtPlus(s);
      if (l(l) > 1 && all isInteger(l))
        ret setOp(f plus, l);

      l = splitAtMinus(s);
      if (l(l) > 1 && all isInteger(l))
        ret setOp(f minus, l);

      false;
    }
    
    bool setOp(S op, LS args) {
      this.op = op;
      arguments = map bigint(args);
      true;
    }
    
    run {
      say(str(foldl_noSeed(op, arguments)));
    }
  }
  
  *() {
    standardAttractors(new CalcAttractor);
  }
}

Began life as a copy of #1023143