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C++中的解释器模式

news 2025/8/11 4:43:31

解释器模式（Interpreter Pattern）

实际应用

算术表达式解释器

布尔表达式解释器

总结

解释器模式（Interpreter Pattern）

解释器模式是一种行为设计模式，它定义了一种语言的文法表示，并使用解释器来解释这些文法。该模式适用于那些有特定语法规则的场景，比如编译器、正则表达式引擎和计算器。

实际应用

算术表达式解释器

算术表达式解释器 -- 可以解析和计算包含加法和减法的算术表达式。

#include <iostream>
#include <string>
#include <stack>
#include <memory>
#include <unordered_map>// 抽象表达式
class Expression {
public:virtual ~Expression() = default;virtual int interpret(const std::unordered_map<char, int>& context) = 0;
};// 终结符表达式（变量）
class VariableExpression : public Expression {
private:char name;
public:VariableExpression(char name) : name(name) {}int interpret(const std::unordered_map<char, int>& context) override {return context.at(name);}
};// 非终结符表达式（加法）
class AddExpression : public Expression {
private:std::shared_ptr<Expression> left, right;
public:AddExpression(std::shared_ptr<Expression> left, std::shared_ptr<Expression> right) : left(left), right(right) {}int interpret(const std::unordered_map<char, int>& context) override {return left->interpret(context) + right->interpret(context);}
};// 非终结符表达式（减法）
class SubtractExpression : public Expression {
private:std::shared_ptr<Expression> left, right;
public:SubtractExpression(std::shared_ptr<Expression> left, std::shared_ptr<Expression> right) : left(left), right(right) {}int interpret(const std::unordered_map<char, int>& context) override {return left->interpret(context) - right->interpret(context);}
};// 客户端代码：解析并计算表达式
int main() {std::string expr = "a+b-c";std::unordered_map<char, int> context = {{'a', 5}, {'b', 3}, {'c', 2}};std::stack<std::shared_ptr<Expression>> stack;for (char token : expr) {if (isalpha(token)) {stack.push(std::make_shared<VariableExpression>(token));} else if (token == '+') {auto right = stack.top(); stack.pop();auto left = stack.top(); stack.pop();stack.push(std::make_shared<AddExpression>(left, right));} else if (token == '-') {auto right = stack.top(); stack.pop();auto left = stack.top(); stack.pop();stack.push(std::make_shared<SubtractExpression>(left, right));}}auto expression = stack.top();int result = expression->interpret(context);std::cout << "Result: " << result << std::endl;return 0;
}

布尔表达式解释器

布尔表达式解释器 -- 可以解析和计算包含与（AND）和或（OR）的布尔表达式。

#include <iostream>
#include <string>
#include <stack>
#include <memory>
#include <unordered_map>// 抽象表达式
class Expression {
public:virtual ~Expression() = default;virtual bool interpret(const std::unordered_map<std::string, bool>& context) = 0;
};// 终结符表达式（变量）
class VariableExpression : public Expression {
private:std::string name;
public:VariableExpression(const std::string& name) : name(name) {}bool interpret(const std::unordered_map<std::string, bool>& context) override {return context.at(name);}
};// 非终结符表达式（与操作）
class AndExpression : public Expression {
private:std::shared_ptr<Expression> left, right;
public:AndExpression(std::shared_ptr<Expression> left, std::shared_ptr<Expression> right) : left(left), right(right) {}bool interpret(const std::unordered_map<std::string, bool>& context) override {return left->interpret(context) && right->interpret(context);}
};// 非终结符表达式（或操作）
class OrExpression : public Expression {
private:std::shared_ptr<Expression> left, right;
public:OrExpression(std::shared_ptr<Expression> left, std::shared_ptr<Expression> right) : left(left), right(right) {}bool interpret(const std::unordered_map<std::string, bool>& context) override {return left->interpret(context) || right->interpret(context);}
};// 客户端代码：解析并计算布尔表达式
int main() {std::string expr = "a AND b OR c";std::unordered_map<std::string, bool> context = {{"a", true}, {"b", false}, {"c", true}};std::stack<std::shared_ptr<Expression>> stack;std::istringstream iss(expr);std::string token;while (iss >> token) {if (token == "a" || token == "b" || token == "c") {stack.push(std::make_shared<VariableExpression>(token));} else if (token == "AND") {auto right = stack.top(); stack.pop();auto left = stack.top(); stack.pop();stack.push(std::make_shared<AndExpression>(left, right));} else if (token == "OR") {auto right = stack.top(); stack.pop();auto left = stack.top(); stack.pop();stack.push(std::make_shared<OrExpression>(left, right));}}auto expression = stack.top();bool result = expression->interpret(context);std::cout << "Result: " << std::boolalpha << result << std::endl;return 0;
}