notifyObservers first variant

observer/app.d

@@ -1,14 +1,17 @@
 module observer.app;
-
 import observer.weatherdata;
 import observer.currentconditionsdisplay;
+import observer.heatindexdisplay;
 
 void main()
 {
     WeatherData weatherData = new WeatherData();
     CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);
+    HeatIndexDisplay heatIndexDisplay = new HeatIndexDisplay(weatherData);
 
     weatherData.setMeasurements(80, 65, 30.4f);
     weatherData.setMeasurements(82, 70, 29.2f);
+    weatherData.removeObserver(heatIndexDisplay);
     weatherData.setMeasurements(78, 90, 29.2f);
+    weatherData.setMeasurements(81, 72, 29.5f);
 }

observer/heatindexdisplay.d

@@ -0,0 +1,38 @@
+module observer.heatindexdisplay;
+import observer.displayelement;
+import observer.observer;
+import observer.weatherdata;
+import std.stdio : writeln;
+
+class HeatIndexDisplay : Observer, DisplayElement
+{
+private:
+    float heatIndex;
+    WeatherData weatherData;
+
+    float computeHeatIndex(float t, float rh)
+    {
+        return ((16.923 + (0.185212 * t) + (5.37941 * rh) - (0.100254 * t * rh) + (0.00941695 * (t * t))
+                + (0.00728898 * (rh * rh)) + (0.000345372 * (t * t * rh)) - (0.000814971 * (t * rh * rh))
+                + (0.0000102102 * (t * t * rh * rh)) - (0.000038646 * (t * t * t)) + (0.0000291583 * (rh * rh * rh))
+                + (0.00000142721 * (t * t * t * rh)) + (0.000000197483 * (t * rh * rh * rh))
+                - (0.0000000218429 * (t * t * t * rh * rh)) + 0.000000000843296 * (t * t * rh * rh * rh))
+                - (0.0000000000481975 * (t * t * t * rh * rh * rh)));
+    }
+public:
+    this(WeatherData weatherData)
+    {
+        weatherData.registerObserver(this);
+    }
+
+    override void update(float temperature, float humidity, float pressure)
+    {
+        this.heatIndex = computeHeatIndex(temperature, humidity);
+        display();
+    }
+
+    override void display()
+    {
+        writeln("Heat index is ", heatIndex);
+    }
+}

observer/weatherdata.d

@@ -16,7 +16,9 @@ public:
     
     override void removeObserver(Observer o)
     {
-        observers.remove(observers.countUntil(o));
+        // Вызовет ошибку в случае отсутствия элемента в массиве после его поиска
+        // observers = observers.remove(observers.countUntil(o));
+        observers = remove!(current => current == o)(observers);
     }
 
     override void notifyObservers()