LL1文法分析器c++代码

LL(1)文法分析器的C++代码如下：

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

// 定义文法符号类型
enum SymbolType {
    TERMINAL,   // 终结符
    NONTERMINAL // 非终结符
};

// 定义文法符号结构体
struct Symbol {
    SymbolType type;    // 符号类型
    string name;        // 符号名称
};

// 定义产生式结构体
struct Production {
    Symbol left;        // 产生式左部
    vector<Symbol> right;   // 产生式右部
};

// 定义LL(1)文法分析器类
class LL1Parser {
public:
    LL1Parser(vector<Production> productions, Symbol startSymbol, vector<Symbol> terminals, vector<Symbol> nonterminals, map<Symbol, map<Symbol, Production>> parsingTable) :
        productions(productions), startSymbol(startSymbol), terminals(terminals), nonterminals(nonterminals), parsingTable(parsingTable) {}

    // 分析函数
    bool parse(string input) {
        stack<Symbol> symbolStack;
        symbolStack.push(Symbol{ TERMINAL, "$" }); // 压入结束符
        symbolStack.push(startSymbol);  // 压入开始符号

        int i = 0;
        while (!symbolStack.empty()) {
            Symbol topSymbol = symbolStack.top();
            symbolStack.pop();

            if (topSymbol.type == TERMINAL) {
                if (topSymbol.name == "$" && input[i] == '$') {
                    return true;    // 分析成功
                }
                else if (topSymbol.name == string(1, input[i])) {
                    i++;
                }
                else {
                    return false;   // 分析失败
                }
            }
            else if (topSymbol.type == NONTERMINAL) {
                Production production = parsingTable[topSymbol][Symbol{ TERMINAL, string(1, input[i]) }];
                if (production.left.name != "") {
                    for (int j = production.right.size() - 1; j >= 0; j--) {
                        symbolStack.push(production.right[j]);
                    }
                }
                else {
                    return false;   // 分析失败
                }
            }
        }

        return false;   // 分析失败
    }

private:
    vector<Production> productions; // 产生式集合
    Symbol startSymbol;             // 开始符号
    vector<Symbol> terminals;       // 终结符集合
    vector<Symbol> nonterminals;    // 非终结符集合
    map<Symbol, map<Symbol, Production>> parsingTable; // LL(1)分析表
};

// 测试代码
int main() {
    // 定义文法符号
    Symbol E{ NONTERMINAL, "E" };
    Symbol T{ NONTERMINAL, "T" };
    Symbol F{ NONTERMINAL, "F" };
    Symbol plus{ TERMINAL, "+" };
    Symbol minus{ TERMINAL, "-" };
    Symbol multi{ TERMINAL, "*" };
    Symbol div{ TERMINAL, "/" };
    Symbol lparen{ TERMINAL, "(" };
    Symbol rparen{ TERMINAL, ")" };
    Symbol id{ TERMINAL, "id" };
    Symbol num{ TERMINAL, "num" };

    // 定义产生式
    vector<Production> productions{
        { E, { T, plus, E } },
        { E, { T, minus, E } },
        { E, { T } },
        { T, { F, multi, T } },
        { T, { F, div, T } },
        { T, { F } },
        { F, { lparen, E, rparen } },
        { F, { id } },
        { F, { num } }
    };

    // 定义开始符号
    Symbol startSymbol = E;

    // 定义终结符集合和非终结符集合
    vector<Symbol> terminals{ plus, minus, multi, div, lparen, rparen, id, num };
    vector<Symbol> nonterminals{ E, T, F };

    // 定义LL(1)分析表
    map<Symbol, map<Symbol, Production>> parsingTable{
        { E, {
            { id, productions[0] },
            { num, productions[0] },
            { lparen, productions[0] },
            { plus, productions[0] },
            { minus, productions[1] },
            { multi, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { div, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { rparen, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { Symbol{ TERMINAL, "$" }, productions[0] }
        } },
        { T, {
            { id, productions[3] },
            { num, productions[3] },
            { lparen, productions[3] },
            { plus, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { minus, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { multi, productions[3] },
            { div, productions[3] },
            { rparen, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { Symbol{ TERMINAL, "$" }, productions[3] }
        } },
        { F, {
            { id, productions[7] },
            { num, productions[8] },
            { lparen, productions[6] },
            { plus, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { minus, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { multi, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { div, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { rparen, Production{ Symbol{ NONTERMINAL, "" }, {} } },
            { Symbol{ TERMINAL, "$" }, Production{ Symbol{ NONTERMINAL, "" }, {} } }
        } }
    };

    // 创建LL(1)文法分析器
    LL1Parser parser(productions, startSymbol, terminals, nonterminals, parsingTable);

    // 测试分析函数
    string input = "id+id*id$";
    bool result = parser.parse(input);
    if (result) {
        cout << "分析成功" << endl;
    }
    else {
        cout << "分析失败" << endl;
    }

    return 0;
}