From cfe68e39cc8d52f3ad8c51e78753964a2741730d Mon Sep 17 00:00:00 2001
From: Timerix22 <timerix11@gmail.com>
Date: Mon, 25 Dec 2023 17:32:56 +0600
Subject: [PATCH] Fattakh wrote something

---
 SharpCalculator.Avalonia/MainWindow.axaml    | 616 +++++++++++++++++--
 SharpCalculator.Avalonia/MainWindow.axaml.cs | 108 +++-
 2 files changed, 664 insertions(+), 60 deletions(-)

diff --git a/SharpCalculator.Avalonia/MainWindow.axaml b/SharpCalculator.Avalonia/MainWindow.axaml
index ef684f4..38b9dc8 100644
--- a/SharpCalculator.Avalonia/MainWindow.axaml
+++ b/SharpCalculator.Avalonia/MainWindow.axaml
@@ -1,49 +1,571 @@
-<Window xmlns="https://github.com/avaloniaui"
-        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
-        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-        mc:Ignorable="d" Width="400" Height="500"
-        x:Class="SharpCalculator.Avalonia.MainWindow"
-        Title="SharpCalculator"
-        FontFamily="Consolas"
-        FontSize="24">
-    <Grid Margin="16">
-        <Grid.RowDefinitions>4* 1* 4*</Grid.RowDefinitions>
-        <TextBox Name="Input" TextChanged="Input_OnTextChanged"/>
-        <TextBlock Grid.Row="1" VerticalAlignment="Center">=</TextBlock>
-        <TextBox Name="Output" Grid.Row="1" 
-                 Margin="16 0 0 0" 
-                 VerticalAlignment="Center"
-                 IsReadOnly="True"
-                 BorderThickness="0"
-        />
-        <Grid Grid.Row="2">
-            <Grid.ColumnDefinitions> * * * * </Grid.ColumnDefinitions>
-            <Grid.RowDefinitions> * * * * * </Grid.RowDefinitions>
-            <Button Grid.Row="1" Grid.Column="0" Click="MathButton_OnClick">7</Button>
-            <Button Grid.Row="1" Grid.Column="1" Click="MathButton_OnClick">8</Button>
-            <Button Grid.Row="1" Grid.Column="2" Click="MathButton_OnClick">9</Button>
-            
-            <Button Grid.Row="2" Grid.Column="0" Click="MathButton_OnClick">4</Button>
-            <Button Grid.Row="2" Grid.Column="1" Click="MathButton_OnClick">5</Button>
-            <Button Grid.Row="2" Grid.Column="2" Click="MathButton_OnClick">6</Button>
-            
-            <Button Grid.Row="3" Grid.Column="0" Click="MathButton_OnClick">1</Button>
-            <Button Grid.Row="3" Grid.Column="1" Click="MathButton_OnClick">2</Button>
-            <Button Grid.Row="3" Grid.Column="2" Click="MathButton_OnClick">3</Button>
-            
-            <Button Grid.Row="4" Grid.Column="0" Click="MathButton_OnClick">0</Button>
-            <Button Grid.Row="4" Grid.Column="1" Click="MathButton_OnClick">.</Button>
-            <Button Grid.Row="4" Grid.Column="2" Click="MathButton_OnClick">^</Button>
-            
-            <Button Grid.Row="1" Grid.Column="3" Click="MathButton_OnClick">/</Button>
-            <Button Grid.Row="2" Grid.Column="3" Click="MathButton_OnClick">*</Button>
-            <Button Grid.Row="3" Grid.Column="3" Click="MathButton_OnClick">-</Button>
-            <Button Grid.Row="4" Grid.Column="3" Click="MathButton_OnClick">+</Button>
-            
-            <Button Grid.Row="0" Grid.Column="0" Click="ClearButton_OnClick">CLR</Button>
-            <Button Grid.Row="0" Grid.Column="2" Click="MathButton_OnClick">(</Button>
-            <Button Grid.Row="0" Grid.Column="3" Click="MathButton_OnClick">)</Button>
-        </Grid>
+<Window
+    FontFamily="Consolas"
+    FontSize="24"
+    Height="750"
+    Title="SharpCalculator"
+    Width="600"
+    mc:Ignorable="d"
+    x:Class="SharpCalculator.Avalonia.MainWindow"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+
+    <Grid
+        HorizontalAlignment="Center"
+        Margin="20"
+        VerticalAlignment="Center">
+        <Grid.ColumnDefinitions>* * * * * * *</Grid.ColumnDefinitions>
+
+        <Grid.RowDefinitions>* * * * * * * * * *</Grid.RowDefinitions>
+
+        <!--  1st row  -->
+
+        <TextBlock
+            FontSize="40"
+            Grid.Column="0"
+            Grid.ColumnSpan="7"
+            Grid.Row="1"
+            HorizontalAlignment="Right"
+            Name="Input"
+            Text="" />
+
+        <!--  2nd row  -->
+
+        <Button
+            Background="Gray"
+            Click="ClearButton_OnClick"
+            Content="AC"
+            Grid.Column="0"
+            Grid.Row="2"
+            Name="ClearButton"/>
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="("
+            CornerRadius="30"
+            Grid.Column="1"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content=")"
+            CornerRadius="30"
+            Grid.Column="2"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+        <Button
+            Background="Orange"
+            Click="MathButton_OnClick"
+            Content="/"
+            CornerRadius="30"
+            Grid.Column="3"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="^"
+            CornerRadius="30"
+            Grid.Column="4"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="sin"
+            CornerRadius="30"
+            Grid.Column="5"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="asin"
+            CornerRadius="30"
+            Grid.Column="6"
+            Grid.Row="2"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <!--  3rd row  -->
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="7"
+            CornerRadius="30"
+            Grid.Column="0"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="8"
+            CornerRadius="30"
+            Grid.Column="1"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+        <Button
+            Click="MathButton_OnClick"
+            Content="9"
+            CornerRadius="30"
+            Grid.Column="2"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+        <Button
+            Background="Orange"
+            Click="MathButton_OnClick"
+            Content="*"
+            CornerRadius="30"
+            Grid.Column="3"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="e"
+            CornerRadius="30"
+            Grid.Column="4"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="cos"
+            CornerRadius="30"
+            Grid.Column="5"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="acos"
+            CornerRadius="30"
+            Grid.Column="6"
+            Grid.Row="3"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <!--  4th row  -->
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="4"
+            CornerRadius="30"
+            Grid.Column="0"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="5"
+            CornerRadius="30"
+            Grid.Column="1"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="6"
+            CornerRadius="30"
+            Grid.Column="2"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Orange"
+            Click="MathButton_OnClick"
+            Content="-"
+            CornerRadius="30"
+            Grid.Column="3"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="10^x"
+            CornerRadius="30"
+            Grid.Column="4"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="tan"
+            CornerRadius="30"
+            Grid.Column="5"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="atan"
+            CornerRadius="30"
+            Grid.Column="6"
+            Grid.Row="4"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <!--  5th row  -->
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="1"
+            CornerRadius="30"
+            Grid.Column="0"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="2"
+            CornerRadius="30"
+            Grid.Column="1"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="3"
+            CornerRadius="30"
+            Grid.Column="2"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Orange"
+            Click="MathButton_OnClick"
+            Content="+"
+            CornerRadius="30"
+            Grid.Column="3"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="rand"
+            CornerRadius="30"
+            Grid.Column="4"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="ctg"
+            CornerRadius="30"
+            Grid.Column="5"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="actg"
+            CornerRadius="30"
+            Grid.Column="6"
+            Grid.Row="5"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <!--  6th row  -->
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="0"
+            CornerRadius="30"
+            Grid.Column="0"
+            Grid.Row="6"
+            Height="55"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="%"
+            CornerRadius="30"
+            Grid.Column="1"
+            Grid.Row="6"
+            Height="55"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Click="MathButton_OnClick"
+            Content="."
+            CornerRadius="30"
+            Grid.Column="2"
+            Grid.Row="6"
+            Height="55"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Orange"
+            Click="ResultButton_OnClick"
+            Content="="
+            CornerRadius="30"
+            Grid.Column="3"
+            Grid.Row="6"
+            Height="55"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="π"
+            CornerRadius="30"
+            Grid.Column="4"
+            Grid.Row="6"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="1/x"
+            CornerRadius="30"
+            Grid.Column="5"
+            Grid.Row="6"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <Button
+            Background="Gray"
+            Click="MathButton_OnClick"
+            Content="log"
+            CornerRadius="30"
+            Grid.Column="6"
+            Grid.Row="6"
+            Height="60"
+            HorizontalAlignment="Center"
+            HorizontalContentAlignment="Center"
+            Margin="5"
+            VerticalAlignment="Center"
+            VerticalContentAlignment="Center"
+            Width="60" />
+
+        <!--  7th row  -->
+
+        <TextBlock
+            FontSize="25"
+            Grid.Column="0"
+            Grid.ColumnSpan="7"
+            Grid.Row="7"
+            Name="History1"
+            Text="" />
+
+        <!--  8th row  -->
+
+        <TextBlock
+            FontSize="25"
+            Grid.Column="0"
+            Grid.ColumnSpan="7"
+            Grid.Row="8"
+            Name="History2"
+            Text="" />
+
+        <!--  9th row  -->
+
+        <TextBlock
+            FontSize="25"
+            Grid.Column="0"
+            Grid.ColumnSpan="7"
+            Grid.Row="9"
+            Name="History3"
+            Text="" />
     </Grid>
 </Window>
\ No newline at end of file
diff --git a/SharpCalculator.Avalonia/MainWindow.axaml.cs b/SharpCalculator.Avalonia/MainWindow.axaml.cs
index 3a808bd..e7835f9 100644
--- a/SharpCalculator.Avalonia/MainWindow.axaml.cs
+++ b/SharpCalculator.Avalonia/MainWindow.axaml.cs
@@ -1,14 +1,33 @@
+// 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
+// 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;
+using Avalonia.Media;
+
 
 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>();
+    
     public MainWindow()
     {
         InitializeComponent();
@@ -16,32 +35,95 @@ public partial class MainWindow : Window
 
     private void MathButton_OnClick(object? sender, RoutedEventArgs e)
     {
-        if (sender is not Button button)
+        if (sender is not Button button) // Checking if button exist, if not throw Exception
             throw new Exception();
-        string text = button.Content!.ToString()!;
-        Input.Text += text;
+
+        string text; // declaring text for using it in switch case 
+        
+        ClearButton.Content = "AC"; // clear button content changing to Accurate Clear mode
+        
+        switch (Input.Text) // Switch case for checking the inputting functions
+        {
+            case "rand": // rand function add random variable from 0 to 1 into Input 
+                Input.Text = "";
+                Input.Text += _randomNumber.ToString(CultureInfo.InvariantCulture);
+                break;
+            case "π": // Pi function add pi value into Input
+                Input.Text = "";
+                Input.Text += "3.1415";
+                break;
+            case "e": // euler function add e value into Input
+                Input.Text = "";
+                Input.Text += "2.71828";
+                break;
+            case "10^x": // ten in power of x function 
+                Input.Text = "";
+                Input.Text += "10^";
+                break;
+            case "1/x": // one over x function
+                Input.Text = "";
+                Input.Text += "1/";
+                break;
+            default: // if there is no function input, then just input Button content
+                text = button.Content!.ToString()!;
+                Input.Text += text;
+                break;
+        }
     }
 
     private void ClearButton_OnClick(object? sender, RoutedEventArgs e)
     {
-        Input.Text = "";
-        Output.Text = "";
+        // Checking the indexes and the emptiness of the input for clearing one by one
+        if (Input.Text != "" && _currentIndex < Input.Text!.Length)
+        {
+            if ((string)ClearButton.Content! == "AC") // if clear button content equal to AC, clear one by one
+            {
+                Input.Text = Input.Text.Remove(_currentIndex, 1);
+                _currentIndex++;
+            }
+            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 Input_OnTextChanged(object? sender, TextChangedEventArgs e)
+    
+    private void ResultButton_OnClick(object? sender, RoutedEventArgs e)
     {
-        if(Input.Text == null)
+        History1.Foreground = new SolidColorBrush(Colors.Gray);
+        History2.Foreground = new SolidColorBrush(Colors.Gray);
+        History3.Foreground = new SolidColorBrush(Colors.Gray);
+        
+        if(Input.Text == null) // checking Input for nullability 
             return;
-        string exprStr = Input.Text;
+        string exprStr = Input.Text; // expression variable, for print result
         try
         {
-            double rezult = Calculator.Calculate(exprStr);
-            if(!double.IsNaN(rezult))
-                Output.Text = rezult.ToString(CultureInfo.InvariantCulture);
+            double rezult = Calculator.Calculate(exprStr); // result being processed by calculator object that implemented in FusionCalculator Module
+            if (!double.IsNaN(rezult))
+            {
+                Input.Text = rezult.ToString(CultureInfo.InvariantCulture);
+                _history.Add(rezult.ToString(CultureInfo.InvariantCulture));
+            }
         }
         catch (Exception exception)
         {
-            Debug.WriteLine(exception.ToString());
+            Input.Text = "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
     }
 }
\ No newline at end of file