import std.stdio;

struct Portfolio {
  double[string] data;
  // ...
}

struct HedgeRecommendation {
  string recommendation;
  this(int) {
    recommendation = "Sell, the market is rigged";
  }
}

struct Analyzer {
  immutable(Portfolio) portfolio;
  this(ref immutable(Portfolio) portfolio) {
    this.portfolio = portfolio;
  }

  HedgeRecommendation createHedge() {
    auto result = HedgeRecommendation(1);
    //...
    return result;
  }
}

Portfolio readPortfolio(string id) {
  // read portfolio from database
  return Portfolio([ "IBM" : 100.0, "SPY" : 300.0 ]);
}

HedgeRecommendation getHedgeRecommendation(string portfolioId) {
  auto portfolio = cast(immutable)readPortfolio(portfolioId);
  auto analyzer = Analyzer(portfolio);
  return analyzer.createHedge();
}

void main() {
  writeln(getHedgeRecommendation("1234"));
}