More code style improvements

Author: daniel-lerch

src/Vocup/IO/Vhf1Format2.cs

@@ -186,8 +186,11 @@ private async ValueTask ReadResults(Book book, string fileName, string vhrCode,
             for (int i = 0; i < book.Words.Count; i++)
             {
                 Word word = book.Words[i];
+
+                // Same practice history for all synonyms. Using the same references is fine as they are immutable.
                 var motherTonguePracticeHistory = GeneratePracticeHistory(results[i].stateNumber, results[i].date, book.PracticeMode != PracticeMode.AskForForeignLang);
                 var foreignLanguagePracticeHistory = GeneratePracticeHistory(results[i].stateNumber, results[i].date, book.PracticeMode != PracticeMode.AskForMotherTongue);
+                
                 foreach (Synonym motherTongue in word.MotherTongue)
                 {
                     motherTongue.Practices.AddRange(motherTonguePracticeHistory);

src/Vocup/ViewModels/SynonymViewModel.cs

@@ -31,36 +31,36 @@ public SynonymViewModel(WordViewModel parent, Synonym synonym)
     private static double GetPracticeState(IReadOnlyCollection<Practice> practices)
     {
         // Zipf's law weighted average for the last 5 practices
-        int lastN = 5;
+        int maxPracticesToConsider = 5;
 
-        double values = 0.0, weights = 0.0;
-        int counter = 1;
+        double weightedSum = 0.0, sumOfWeights = 0.0;
+        int practicePosition = 1;
 
-        foreach (Practice practice in practices.Reverse().Take(lastN))
+        foreach (Practice practice in practices.Reverse().Take(maxPracticesToConsider))
         {
-            double weight = 1.0 / counter;
+            double weight = 1.0 / practicePosition;
             double result = practice.Result switch
             {
                 PracticeResult2.Correct => 1.0,
                 PracticeResult2.PartlyCorrect => 0.5,
                 PracticeResult2.Wrong => 0.0,
                 _ => throw new ArgumentOutOfRangeException(null, practice.Result, "Invalid practice result")
             };
-            values += result * weight;
-            weights += weight;
-            counter++;
+            weightedSum += result * weight;
+            sumOfWeights += weight;
+            practicePosition++;
         }
 
-        if (counter == 1)
+        if (practicePosition == 1)
             return -1.0; // No practices
 
-        for (; counter <= lastN; counter++)
+        for (; practicePosition <= maxPracticesToConsider; practicePosition++)
         {
             // Assume 0.0 for missing practices
-            weights += 1.0 / counter;
+            sumOfWeights += 1.0 / practicePosition;
         }
 
-        return values / weights;
+        return weightedSum / sumOfWeights;
     }
 
     public void Dispose()