1 using System;
 2 using System.Collections;
 3 
 4 namespace Calculator
 5 {
 6     public class SymbolTable
 7     {
 8         static SymbolTable() : instance(new SymbolTable())
 9         {
10         }
11         public static SymbolTable& Instance()
12         {
13             return *instance;
14         }
15         private SymbolTable() : variableMap()
16         {
17         }
18         public void SetVariable(const ustring& variableName, double variableValue)
19         {
20             variableMap[variableName] = variableValue;
21         }
22         public Result<double> GetVariableValue(const ustring& variableName)
23         {
24             Map<ustring, double>.ConstIterator it = variableMap.CFind(variableName);
25             if (it != variableMap.CEnd())
26             {
27                 double value = it->second;
28                 return value;
29             }
30             else
31             {
32                 auto utf8Result = ToUtf8(variableName);
33                 if (utf8Result.Error())
34                 {
35                     return Result<double>(ErrorId(utf8Result.GetErrorId()));
36                 }
37                 string variableNameValue = utf8Result.Value();
38                 int errorId = AllocateError("variable \'" + variableNameValue + "\' not found");
39                 return Result<double>(ErrorId(errorId));
40             }
41         }
42         public void Print()
43         {
44             Console.WriteLine("variables:");
45             for (const Pair<ustring, double>& pair : variableMap)
46             {
47                 Console.Out() << pair.first << " = " << pair.second << endl();
48             }
49         }
50         private static UniquePtr<SymbolTable> instance;
51         private Map<ustring, double> variableMap;
52     }