用C++写一个三地址代码生成器

下面是一个简单的 C++ 三地址代码生成器示例，可以将简单的表达式转换为对应的三地址码：

#include <iostream>
#include <stack>
using namespace std;

// 定义操作符和操作数类型
enum TokenType { OPERATOR, OPERAND };

// 定义操作符类型和优先级
enum OperatorType { ADD, SUB, MUL, DIV };
const int OperatorPrecedence[] = {0, 0, 1, 1};

// 定义 token 结构体
struct Token {
    TokenType type;
    union {
        OperatorType op;
        int value;
    };
};

// 定义栈操作函数
void push_token(stack<Token>& tokenStack, Token token) {
    tokenStack.push(token);
}

Token pop_token(stack<Token>& tokenStack) {
    Token token = tokenStack.top();
    tokenStack.pop();
    return token;
}

Token top_token(stack<Token>& tokenStack) {
    return tokenStack.top();
}

bool is_operator(Token token) {
    return token.type == OPERATOR;
}

// 定义三地址码生成函数
void generate_three_address_code(stack<Token>& tokenStack) {
    stack<string> codeStack;
    Token token = pop_token(tokenStack);
    while (true) {
        if (is_operator(token)) {
            Token right = pop_token(tokenStack);
            Token left = pop_token(tokenStack);
            string result = "t" + to_string(codeStack.size() + 1);
            string op;
            switch (token.op) {
                case ADD:
                    op = "+";
                    break;
                case SUB:
                    op = "-";
                    break;
                case MUL:
                    op = "*";
                    break;
                case DIV:
                    op = "/";
                    break;
            }
            string code = result + " = " + to_string(left.value) + " " + op + " " + to_string(right.value);
            codeStack.push(code);
            push_token(tokenStack, Token{OPERAND, {static_cast<int>(codeStack.size())}});
        } else {
            codeStack.push(to_string(token.value));
        }
        if (tokenStack.empty()) {
            break;
        }
        token = pop_token(tokenStack);
    }
    while (!codeStack.empty()) {
        cout << codeStack.top() << endl;
        codeStack.pop();
    }
}

int main() {
    stack<Token> tokenStack;
    push_token(tokenStack, Token{OPERAND, {1}});
    push_token(tokenStack, Token{OPERAND, {2}});
    push_token(tokenStack, Token{OPERATOR, {ADD}});
    push_token(tokenStack, Token{OPERAND, {3}});
    push_token(tokenStack, Token{OPERATOR, {MUL}});
    push_token(tokenStack, Token{OPERAND, {4}});
    push_token(tokenStack, Token{OPERATOR, {SUB}});
    push_token(tokenStack, Token{OPERAND, {5}});
    push_token(tokenStack, Token{OPERATOR, {DIV}});

    generate_three_address_code(tokenStack);

    return 0;
}

这个示例实现了一个简单的逆波兰表达式求值器，首先将表达式转换为逆波兰表达式，然后使用栈来计算表达式的值。在计算的过程中，生成对应的三地址码，最后输出生成的三地址码。这个示例只支持四则运算，更复杂的表达式和语法需要更复杂的实现。