C++二十三种设计模式之表明器模式 - IT评测·应用市场-qidao123.com

#include<iostream>
#include <vector>
#include <list>
#include <string>
#include <mutex>
#include <map>
#include<stack>
using namespace std;
class Expression;//抽象表达式类
class VarExpression;//终结符表达式类
class SymbolExpression;//抽象非终结符表达式类
class AddExpression;//具体非终结符表达式类
class SubExpression;//具体非终结符表达式类
Expression* analyse(string strExp);//解析函数
class Expression {
public:
Expression(int num, char sign) : m_num_dbg(num), m_sign_dbg(sign) {}
virtual int interpret(map <char, int> var) = 0;
virtual ~Expression() {};
int m_num_dbg;
char m_sign_dbg;
};
class VarExpression : public Expression {
public:
VarExpression(const char& key, int num, char sign) : Expression(num, sign), m_key(key) {}
int interpret(map <char, int> var) {
return var[m_key];
};
~VarExpression() {
cout << "delete VarExpression num:" << m_num_dbg << " sign:" << m_sign_dbg << endl;
};
private:
char m_key;
};
class SymbolExpression : public Expression {
public:
SymbolExpression(Expression* left, Expression* right, int num, char sign) : Expression(num, sign), m_left(left), m_right(right) {}
Expression* GetLeft() {
return m_left;
};
Expression* GetRight() {
return m_right;
};
~SymbolExpression() {
delete m_left;
delete m_right;
cout << "delete SymbolExpression num:" << m_num_dbg << " sign:" << m_sign_dbg << endl;
}
protected:
Expression* m_left;
Expression* m_right;
};
class AddExpression : public SymbolExpression {
public:
AddExpression(Expression* left, Expression* right, int num, char sign) : SymbolExpression(left, right, num, sign) {}
int interpret(map <char, int> var) {
int value1 = m_left->interpret(var);
int value2 = m_right->interpret(var);
int result = value1 + value2;
return result;
};
~AddExpression() {};
};
class SubExpression : public SymbolExpression {
public:
SubExpression(Expression* left, Expression* right, int num, char sign) : SymbolExpression(left, right, num, sign) {}
int interpret(map <char, int> var) {
int value1 = m_left->interpret(var);
int value2 = m_right->interpret(var);
int result = value1 - value2;
return result;
};
};
Expression* analyse(string strExp) {
stack<Expression*> expStack;
Expression* left;
Expression* right;
int iCount = 0;
for (size_t i = 0; i < strExp.size(); i++) {
switch (strExp[i]) {
case '+':
left = expStack.top();
++i;
right = new VarExpression(strExp[i], iCount++, 'v');
expStack.push(new AddExpression(left, right, iCount++, '+'));
break;
case '-':
left = expStack.top();
++i;
right = new VarExpression(strExp[i], iCount++, 'v');
expStack.push(new SubExpression(left, right, iCount++, '-'));
break;
default:
expStack.push(new VarExpression(strExp[i], iCount++, 'v'));
break;
}
}
return expStack.top();
}
int main() {
string expStr = "a+b-c";
map<char, int> var;
var.insert({ 'a',1 });
var.insert({ 'b',3 });
var.insert({ 'c',2 });
unique_ptr<Expression> exp(analyse(expStr));
int result = (exp)->interpret(var);
for (auto iter = var.begin(); iter != var.end(); iter++) {
cout << iter->first << ":" << iter->second << endl;
}
cout << expStr << "=" << result << endl;
}

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