1 import UIKit
 2 
 3 class ViewController: UIViewController {
 4     
 5     override func viewDidLoad() {
 6         super.viewDidLoad()
 7         // Do any additional setup after loading the view, typically from a nib.
 8         
 9         //添加一个异常捕捉语句
10         do
11         {
12             //字符串计算方法，求和
13             let value = try "1+2".evaluate()
14             //控制台输出计算的结果
15             print("1+2 = \(value)")
16             
17             //初始化一个算术表达式
18             let expression = try Expression(string: "1+2*3/4-5")
19             //创建一个计算器对象
20             let evaluator: Evaluator = Evaluator()
21             //通过调用计算器对象的计算命令，计算字符串中的算术表达式
22             let value2 = try evaluator.evaluate(expression)
23             //在控制台输出算术表达式计算的结果。
24             print("1+2*3/4-5 = \(value2)")
25             
26             //幂运算
27             let value3 = try "1 + 2⁽³⁺¹⁻²⁾".evaluate()
28             //控制台输出计算的结果
29             print("1 + 2⁽³⁺¹⁻²⁾ = \(value3)")
30             
31             //识别特殊数学符号，如½
32             let value4 = try "12 * ½".evaluate()
33             //控制台输出计算的结果
34             print("12 * ½ = \(value4)")
35         }
36         catch
37         {
38             print("Something went wrong :(")
39         }
40     }
41     
42     override func didReceiveMemoryWarning() {
43         super.didReceiveMemoryWarning()
44         // Dispose of any resources that can be recreated.
45     }
46 }