知识点：
1.System.Math.Pow() 实现乘方
2.实现计算器的运算优先级，依次调用的流程
问题：
还未实现“()”功能
解决方案
UI:
1 using System;
2 using System.Collections.Generic;
3 using System.ComponentModel;
4 using System.Data;
5 using System.Drawing;
6 using System.Text;
7 using System.Windows.Forms;
8
9 namespace CaculationTest
10 {
11 public partial class Form1 : Form
12 {
13 public Form1()
14 {
15 InitializeComponent();
16 }
17
18 private void button_Click(object sender, EventArgs e)
19 {
20 var text=((Button)sender).Text;
21 if (text == "=")
22 {
23 Evaluate();
24 }
25 else
26 {
27 txtExpression.Text = txtExpression.Text + text;
28 }
29 }
30
31 private void Evaluate()
32 {
33 txtExpression.Text = new Caculator().Evaluate(txtExpression.Text).ToString();
34 }
35
36 private void button16_Click(object sender, EventArgs e)
37 {
38 txtExpression.Clear();
39 }
40
41
42 }
43 }
Form1.cs
1 using System;
2 using System.Collections.Generic;
3 using System.Text;
4
5 namespace CaculationTest
6 {
7 enum TokenType
8 {
9 Add,Sub,
10 Mul,Div,
11 Int,
12 Expo,
13 Start,End
14 }
15
16 class Token
17 {
18 public TokenType Type;
19 public object Value;
20
21
22 public Token(TokenType type , object value = null)
23 {
24 Type = type;
25 Value = value;
26 }
27 }
28 }
Token.cs
1 using System;
2 using System.Collections.Generic;
3 using System.Text;
4
5 namespace CaculationTest
6 {
7 /// <summary> </summary>
8 abstract class Expression
9 {
10 public abstract int GetValue();
11 }
12
13 class UnaryExpress : Expression
14 {
15 int _value;
16
17 public UnaryExpress(int value)
18 {
19 _value = value;
20 }
21
22
23 public override int GetValue()
24 {
25 return _value;
26 }
27 }
28
29
30 class BinaryExpression : Expression
31 {
32 TokenType _tokenType;
33 int _left;
34 int _right;
35
36
37 public BinaryExpression(TokenType tokenType, Expression left, Expression right)
38 {
39 _tokenType = tokenType;
40 _left = left.GetValue();
41 _right = right.GetValue();
42 }
43
44 public override int GetValue()
45 {
46 switch (_tokenType)
47 {
48 case TokenType.Add:
49 return _left + _right;
50 case TokenType.Sub:
51 return _left - _right;
52 case TokenType.Mul:
53 return _left * _right;
54 case TokenType.Div:
55 return _left / _right;
56 case TokenType.Expo:
57 return Convert.ToInt32(Math.Pow(_left,_right));
58 default:
59 throw new Exception("unexceptional token!");
60 }
61 }
62 }
63 }
Expression.cs
1 using System;
2 using System.Collections.Generic;
3 using System.Text;
4
5
6 namespace CaculationTest
7 {
8 /// <summary> </summary>
9 class Caculator
10 {
11 string _exp;
12
13 int _pos;
14 Token _token;
15 int _len;
16
17
18 public int Evaluate(string expression)
19 {
20 _exp = expression;
21 _len = expression.Length;
22 var exp = ParseExpression();
23 return exp.GetValue();
24 }
25
26 Expression ParseExpression()
27 {
28 //先解析一次，解析内容存在_token中
29 ParseToken();
30 return ParseAddSub();
31 }
32
33 //解析加减
34 Expression ParseAddSub()
35 {
36 //左操作数为优先级理高的运算符
37 var l = ParseMulDiv();
38 while (_token.Type == TokenType.Add || _token.Type == TokenType.Sub)
39 {
40 var t = _token.Type;
41 ParseToken();
42 var r = ParseMulDiv();//解析右操作数
43 l = new BinaryExpression(t, l, r);
44 }
45 return l;
46 }
47
48 #region 老逻辑
49 ////解析乘除
50 //Expression ParseMulDiv()
51 //{
52 // var l = ParseUnary();
53 // while (_token.Type == TokenType.Mul || _token.Type == TokenType.Div)
54 // {
55 // var t = _token.Type;
56 // ParseToken();
57 // var r=ParseUnary();
58 // l = new BinaryExpression(t, l, r);
59 // }
60 // return l;
61 //}
62 #endregion
63
64 //解析乘除
65 Expression ParseMulDiv()
66 {
67 var l = ParseExpo();
68 while (_token.Type == TokenType.Mul || _token.Type == TokenType.Div)
69 {
70 var t = _token.Type;
71 ParseToken();
72 var r = ParseExpo();
73 l = new BinaryExpression(t, l, r);
74 }
75 return l;
76 }
77
78 //解析乘方
79 Expression ParseExpo()
80 {
81 var l = ParseUnary();
82 while (_token.Type==TokenType.Expo)
83 {
84 var t = _token.Type;
85 ParseToken();
86 var r = ParseUnary();
87 l = new BinaryExpression(t, l, r);
88 }
89 return l;
90 }
91
92 //解析一元表达式（目前只有单个整数）
93 Expression ParseUnary()
94 {
95 Expression ret = null;
96 if (_token.Type == TokenType.Int)
97 {
98 ret= new UnaryExpress((int)_token.Value);
99 }
100
101 //解析完int后，移到下一个token处，即+-*/
102 ParseToken();
103 return ret;
104 }
105
106
107 void ParseToken()
108 {
109 //已结束
110 if (_pos >= _len)
111 {
112 _token= new Token(TokenType.End);
113 return;
114 }
115
116 //跳过空格
117 while (_exp[_pos] == ‘ ‘)
118 {
119 _pos++;
120 }
121
122 //如果以数字开头，解析整数
123 if (_exp[_pos] >= ‘0‘ && _exp[_pos] <= ‘9‘)
124 {
125 for (int i = 0; i + _pos <= _len; i++)
126 {
127 //如果以数字结尾，或者到达了数字的边界
128 if( i+_pos==_len||(_exp[_pos + i] < ‘0‘ || _exp[_pos + i] > ‘9‘))
129 {
130 var intStr = _exp.Substring(_pos, i);
131 var value = int.Parse(intStr);
132 _token= new Token(TokenType.Int, value);
133 _pos += i; //解析成功后，更新当前位置
134 break;
135 }
136 }
137 }
138 else
139 {
140 switch (_exp[_pos])
141 {
142 case ‘+‘:
143 _token=new Token(TokenType.Add);
144 break;
145 case ‘-‘:
146 _token = new Token(TokenType.Sub);
147 break;
148 case ‘*‘:
149 _token=new Token(TokenType.Mul);
150 break;
151 case ‘/‘:
152 _token = new Token(TokenType.Div);
153 break;
154 case ‘^‘:
155 _token=new Token(TokenType.Expo);
156 break;
157 default:
158 throw new Exception("unexpected token: " + _exp[_pos]);
159 }
160 _pos++;//解析成功后，更新当前位置
161 }
162 }
163
164 }
165 }
Calculator.cs
验证结果
时间： 2024-11-10 14:34:42