void populateSlippageCache(Symbol symbol)
{
var manager = new SpudManager();
var bars = bars_[symbol];
var spud = new BarSpud(manager);
var calculator = symbol.slippageCalculator(spud);
each(sort(bars.Keys), date => {
spud.set(bars[date]);
slippageCache.get(date)[symbol] = calculator.slippage();
manager.newBar();
});
}