latest fixes from Fattakh

SharpCalculator.Avalonia/MainWindow.axaml

@@ -36,9 +36,17 @@
             Background="Gray"
             Click="ClearButton_OnClick"
             Content="AC"
+            CornerRadius="30"
             Grid.Column="0"
             Grid.Row="2"
-            Name="ClearButton"/>
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            Name="ClearButton"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
 
         <Button
             Background="Gray"

SharpCalculator.Avalonia/MainWindow.axaml.cs

@@ -1,17 +1,14 @@
 // This implementation of the calculator using
 // multi-translating programming language Fusion.
 // The main logic was written on the Fusion, 
-// then retranslated into c#, 'out' module in FusionCalculator
+// then translated into c#, 'out' module in FusionCalculator
 // is a translated c# code, that used by SharpCalculator module.
 // If you want to dive into the logic of the calculator,
 // you need to check 'out' folder in FusionCalculator module.
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Globalization;
-using System.Linq;
-using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Interactivity;
 using FusionCalculator;
@@ -22,23 +19,47 @@ namespace SharpCalculator.Avalonia;
 
 public partial class MainWindow : Window
 {
-    static Random _random = new Random(); // Random object for rand() function in calculator
-    double _randomNumber = _random.NextDouble(); // Random variable is between 0 to 1
-    private int _currentIndex = 0; // Current index for checking the length of input text, accordingly for clear button
-    
-    private List<string> _history = new List<string>();
+    private static readonly Random Random = new Random(); // Random object for rand() function in calculator
+    private readonly double _randomNumber = Random.NextDouble(); // Random variable is between 0 to 1
+    private readonly List<string> _history = new List<string>(); // History list to append expressions
     
     public MainWindow()
     {
         InitializeComponent();
     }
     
+    private void AppendToHistory(string calculation) //function of appending expression to the history list
+    {
+        _history.Add(calculation);
+        UpdateHistoryText();
+    }
+
+    private void UpdateHistoryText() //function to update history list 
+    {
+        int lastIndex = _history.Count - 1;
+
+        if (lastIndex >= 0)
+        {
+            History1.Text = _history[lastIndex];
+        }
+
+        if (lastIndex - 1 >= 0)
+        {
+            History2.Text = _history[lastIndex - 1];
+        }
+
+        if (lastIndex - 2 >= 0)
+        {
+            History3.Text = _history[lastIndex - 2];
+        }
+    }
+
     private void MathButton_OnClick(object? sender, RoutedEventArgs e)
     {
         if (sender is not Button button) // Checking if button exist, if not throw Exception
             throw new Exception();
 
-        string text; // declaring text for using it in switch case 
+        
         
         ClearButton.Content = "AC"; // clear button content changing to Accurate Clear mode
         
@@ -65,33 +86,31 @@ public partial class MainWindow : Window
                 Input.Text += "1/";
                 break;
             default: // if there is no function input, then just input Button content
-                text = button.Content!.ToString()!;
+                string text = button.Content!.ToString()!; // declaring text for using it in switch case 
                 Input.Text += text;
                 break;
         }
     }
     
-    private void ClearButton_OnClick(object? sender, RoutedEventArgs e)
+    private void DeleteLastDigit() // function of deleting the digits and math operators one by one from right, like in real calculators
     {
-        // Checking the indexes and the emptiness of the input for clearing one by one
-        if (Input.Text != "" && _currentIndex < Input.Text!.Length)
+        if (!string.IsNullOrEmpty(Input.Text))
+        {
+            Input.Text = Input.Text.Substring(0, Input.Text.Length - 1);
+        }
+    }
+
+    private void ClearButton_OnClick(object? sender, RoutedEventArgs e)
     {
         if ((string)ClearButton.Content! == "AC") // if clear button content equal to AC, clear one by one
         { 
-                Input.Text = Input.Text.Remove(_currentIndex, 1);
-                _currentIndex++;
+            DeleteLastDigit();
         }
         else if ((string)ClearButton.Content! == "C") // if clear button content equal to C, clear all
         {
                 Input.Text = "";
         }
     }
-        else
-        {
-            // Handle the case when there's no text or all characters are cleared
-            _currentIndex = 0; // Reset the index for the next round
-        }
-    }
     
     private void ResultButton_OnClick(object? sender, RoutedEventArgs e)
     {
@@ -99,31 +118,26 @@ public partial class MainWindow : Window
         History2.Foreground = new SolidColorBrush(Colors.Gray);
         History3.Foreground = new SolidColorBrush(Colors.Gray);
 
+        string inputHistory = Input.Text!;
+        
         if(Input.Text == null) // checking Input for nullability 
             return;
         string exprStr = Input.Text; // expression variable, for print result
         try
         {
-            double rezult = Calculator.Calculate(exprStr); // result being processed by calculator object that implemented in FusionCalculator Module
-            if (!double.IsNaN(rezult))
+            double result = Calculator.Calculate(exprStr); // result being processed by calculator object that implemented in FusionCalculator Module
+            if (!double.IsNaN(result))
             {
-                Input.Text = rezult.ToString(CultureInfo.InvariantCulture);
-                _history.Add(rezult.ToString(CultureInfo.InvariantCulture));
+                Input.Text = result.ToString(CultureInfo.InvariantCulture);
+                AppendToHistory($"{inputHistory} = {result}");
             }
         }
         catch (Exception exception)
         {
-            Input.Text = "Error: "+exception.Message;
+            Input.Text = "Error";
+            AppendToHistory($"Error: {exception.Message}");
         }
 
-        // Display the calculation history in the three TextBlocks
-        if (_history.Count > 0)
-            History1.Text = _history[0];
-        if (_history.Count > 1)
-            History2.Text = _history[1];
-        if (_history.Count > 2)
-            History3.Text = _history[2];
-
         ClearButton.Content = "C"; // if the expression is printed, then change clear button content ot C, for clearing expression totally
     }
 }