用语法制导翻译实现中缀表达式错误检查,并且给出错误信息与错误位置,如果中缀表达式正确,则给出翻译后的逆波兰式,并根据给出的逆波兰式求值,程序使用WPF实现界面,请给出具体代码
时间: 2024-03-24 11:41:16 浏览: 22
好的,这是一个比较复杂的问题,我会尽可能详细地解答。首先,我们需要了解什么是语法制导翻译和逆波兰式。
语法制导翻译是指将源语言文法转换为目标语言文法的一种方法,其中语法分析和翻译过程是相互关联的。在这里,我们可以使用语法制导翻译实现中缀表达式的错误检查和翻译。
逆波兰式,也叫后缀表达式,是一种将运算符写在操作数后面的表达式。例如,中缀表达式“3 + 4”可以转换为后缀表达式“3 4 +”。逆波兰式求值可以通过栈来实现。
现在,我们可以开始讲解具体的实现过程了。首先,我们需要使用WPF实现一个界面,用于输入中缀表达式和显示结果。这里我们可以使用TextBox和Label控件来实现。
```
<Window x:Class="InfixToPostfix.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Infix to Postfix" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Label Content="Enter infix expression:" Grid.Row="0"/>
<TextBox x:Name="InfixTextBox" Grid.Row="1" Margin="10"/>
<Label x:Name="ResultLabel" Content="" Grid.Row="2"/>
</Grid>
</Window>
```
接下来,我们需要实现中缀表达式的翻译和逆波兰式求值。这里我们可以使用一个Stack来实现逆波兰式求值。
```
private double EvaluatePostfix(string postfix)
{
Stack<double> stack = new Stack<double>();
string[] tokens = postfix.Split(' ');
foreach (string token in tokens)
{
if (double.TryParse(token, out double number))
{
stack.Push(number);
}
else
{
double operand2 = stack.Pop();
double operand1 = stack.Pop();
switch (token)
{
case "+":
stack.Push(operand1 + operand2);
break;
case "-":
stack.Push(operand1 - operand2);
break;
case "*":
stack.Push(operand1 * operand2);
break;
case "/":
stack.Push(operand1 / operand2);
break;
default:
throw new ArgumentException("Invalid operator: " + token);
}
}
}
return stack.Pop();
}
private string InfixToPostfix(string infix)
{
Stack<char> stack = new Stack<char>();
StringBuilder postfix = new StringBuilder();
for (int i = 0; i < infix.Length; i++)
{
char c = infix[i];
if (char.IsDigit(c))
{
while (i < infix.Length && char.IsDigit(infix[i]))
{
postfix.Append(infix[i]);
i++;
}
postfix.Append(' ');
i--;
}
else if (c == '+' || c == '-')
{
while (stack.Count > 0 && (stack.Peek() == '+' || stack.Peek() == '-' || stack.Peek() == '*' || stack.Peek() == '/'))
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Push(c);
}
else if (c == '*' || c == '/')
{
while (stack.Count > 0 && (stack.Peek() == '*' || stack.Peek() == '/'))
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Push(c);
}
else if (c == '(')
{
stack.Push(c);
}
else if (c == ')')
{
while (stack.Peek() != '(')
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Pop();
}
else if (!char.IsWhiteSpace(c))
{
throw new ArgumentException("Invalid character: " + c);
}
}
while (stack.Count > 0)
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
return postfix.ToString().Trim();
}
```
最后,我们需要在界面上添加一个按钮,当用户点击按钮时,我们将获取中缀表达式,将其翻译为逆波兰式,并求出结果。如果中缀表达式有错误,我们将显示错误信息和错误位置。
```
private void EvaluateButton_Click(object sender, RoutedEventArgs e)
{
try
{
string infix = InfixTextBox.Text.Trim();
string postfix = InfixToPostfix(infix);
double result = EvaluatePostfix(postfix);
ResultLabel.Content = postfix + " = " + result;
}
catch (Exception ex)
{
ResultLabel.Content = ex.Message;
int index = InfixTextBox.Text.IndexOf(ex.ParamName);
InfixTextBox.Focus();
InfixTextBox.Select(index, ex.ParamName.Length);
}
}
```
完整的代码如下所示:
```
<Window x:Class="InfixToPostfix.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Infix to Postfix" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Label Content="Enter infix expression:" Grid.Row="0"/>
<TextBox x:Name="InfixTextBox" Grid.Row="1" Margin="10"/>
<Button Content="Evaluate" Click="EvaluateButton_Click" Grid.Row="1" HorizontalAlignment="Right" Margin="10"/>
<Label x:Name="ResultLabel" Content="" Grid.Row="2"/>
</Grid>
</Window>
```
```
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void EvaluateButton_Click(object sender, RoutedEventArgs e)
{
try
{
string infix = InfixTextBox.Text.Trim();
string postfix = InfixToPostfix(infix);
double result = EvaluatePostfix(postfix);
ResultLabel.Content = postfix + " = " + result;
}
catch (Exception ex)
{
ResultLabel.Content = ex.Message;
int index = InfixTextBox.Text.IndexOf(ex.ParamName);
InfixTextBox.Focus();
InfixTextBox.Select(index, ex.ParamName.Length);
}
}
private double EvaluatePostfix(string postfix)
{
Stack<double> stack = new Stack<double>();
string[] tokens = postfix.Split(' ');
foreach (string token in tokens)
{
if (double.TryParse(token, out double number))
{
stack.Push(number);
}
else
{
double operand2 = stack.Pop();
double operand1 = stack.Pop();
switch (token)
{
case "+":
stack.Push(operand1 + operand2);
break;
case "-":
stack.Push(operand1 - operand2);
break;
case "*":
stack.Push(operand1 * operand2);
break;
case "/":
stack.Push(operand1 / operand2);
break;
default:
throw new ArgumentException("Invalid operator: " + token);
}
}
}
return stack.Pop();
}
private string InfixToPostfix(string infix)
{
Stack<char> stack = new Stack<char>();
StringBuilder postfix = new StringBuilder();
for (int i = 0; i < infix.Length; i++)
{
char c = infix[i];
if (char.IsDigit(c))
{
while (i < infix.Length && char.IsDigit(infix[i]))
{
postfix.Append(infix[i]);
i++;
}
postfix.Append(' ');
i--;
}
else if (c == '+' || c == '-')
{
while (stack.Count > 0 && (stack.Peek() == '+' || stack.Peek() == '-' || stack.Peek() == '*' || stack.Peek() == '/'))
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Push(c);
}
else if (c == '*' || c == '/')
{
while (stack.Count > 0 && (stack.Peek() == '*' || stack.Peek() == '/'))
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Push(c);
}
else if (c == '(')
{
stack.Push(c);
}
else if (c == ')')
{
while (stack.Peek() != '(')
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
stack.Pop();
}
else if (!char.IsWhiteSpace(c))
{
throw new ArgumentException("Invalid character: " + c, nameof(infix));
}
}
while (stack.Count > 0)
{
postfix.Append(stack.Pop());
postfix.Append(' ');
}
return postfix.ToString().Trim();
}
}
```