// executes things like "hasWord($x) => ..."
sclass AI_ExecuteSimpleForWhere implements Steppable {
  // filled by user (necessary)
  ForWhere fw;
  DeepZipTools tools;
  
  // handle output
  swappable void addLogicRule(BasicLogicRule rule) {}
  
  // iterate values for function
  swappable Iterable elementsForFunction(S functionName) { null; }
  
  // internal variables
  O var;
  S functionName;
  Iterator elements;
  
  *() {}
  *(DeepZipTools *tools, IVF1<BasicLogicRule> *addLogicRule,
    IF1<S, Iterable> *elementsForFunction, ForWhere *fw) {}
  
  public bool step() {
    if (elements == null) {
      Pair p = forWhereParseSimpleFunctionCall(fw, tools);
      if (p == null) false;
      functionName = (S) p.b;
      var = p.a;
      elements = iterator(elementsForFunction(functionName));
    }
    
    if (!elements.hasNext()) false;
    addLogicRule((BasicLogicRule) tools.replaceVars(fw.body, litmap(var, elements.next())));
    true;
  }
}