c++ - Recursive Decent 解析器 (c++) 的编译问题

Question

我的 C++ 程序在编译时遇到问题，它是一个递归的不错的解析器，规则如下:

slist :: = stmt slist | stmt
stmt ::= decl | assign | print
decl ::= INT ID SC | FLOAT ID SC
print ::= PRINT expr SC
assign ::= ID EQUAL expr SC
expr ::=term PLUS expr|term MINUS expr| term
term ::= factor STAR term|factor DIV term| factor MOD term| factor
factor ::= primary STARSTAR factor | primary
primary ::= INTCONST | FLOATCONST | ID |
LPAREN expr RPAREN

我对 C++ 还是比较陌生，所以我不确定是我搞砸了什么还是我的编译器。我在 genome/ubuntu 终端环境中使用 VIM，这些是我在编译时遇到的错误，它看起来像是缺少包含头文件，但我 100% 确定我已经包含了头文件:

我的代码:

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

#include "p3lexer.h"

// this is a list of node types
enum PTreeNodetype {
    SLIST,
    DECL,
    ASSIGN,
    PRINT,
    MATH,
    EQUAL, 
    TERM,
    MINUS,
    STAR,
    MOD,
    STARSTAR
};

// this is a parse tree node
class PTree {
    PTreeNodetype   type;
    PTree *left;
    PTree *right;
public:
    PTree(PTreeNodetype t, PTree *l=0, PTree *r=0) {
        type = t;
        left = l;
        right = r;
    }
};


PTree *Slist();
PTree *Stmt();
PTree *Decl();
PTree *Print();
PTree *Assign();
PTree *Expr();
PTree *Term();
PTree *Factor();
PTree *Primary();

int
main(int argc, char *argv[])
{
    if(argc == 2){
        if(!setLexFile(argv[1]))
            return 0;
    }
    else setLexStdin();


    Token *t;

    // this code just tests the lexer; you should comment it out later
    while( t = getToken() ) {
        cout << t->getType() << ":" << t->getValue() << endl;
        delete t;
    }

    // instead, this code!
    PTree *parse;

    parse = Slist();

    if( parse == 0 ) {
        cout << "Syntax error! " << endl;
        return 0;
    }

    // here... a successful parse means we have to look at the tree
}

// slist :: = stmt slist | stmt
PTree *
Slist() {
    TokenType tt = t->getType();
    //fix this!!
    if(tt != T_SLIST){
        pushbacktoken(t);
        return 0;
    }
    delete t;

    PTree *stmt = Stmt();
    if(!stmt){
        cout << "Syntax error on line " << endl;
    }
    else{
        return new PTree(stmt, slist);
    }
}

// stmt ::= decl | assign | print
PTree *
Stmt() { 
    Token *t = getToken();
    TokenType tt = tt->getType();

    if(tt != T_DECL && T_ASSIGN && T_PRINT){
        pusbbacktoken(t);
        return 0;
    }
    delete t;
    return new(DECL, PRINT, ASSIGN);
}

// decl ::= INT ID SC | FLOAT ID SC
PTree*
Decl(){
    Token *t = getToken();
    TokenType tt = t->getType();

    if(tt != T_INT && tt != T_FLOAT){
        pushbacktoken(t);
        return 0;   
    }

    delete t;

    t = getToken();
    if(t->getToken() != T_ID){
        cout << "Syntax Error!" << endl;

        delete t;
        return 0;
    }

    string id = t->getValue();
    delete t;

    t = getToke();
    if(t->getType() != T_SC){
        cout << "syntax Error! " << endl;

        delete t;
        return 0;
    }
    return new PTree(DECL);
}

//print := PRINT expr SC
PTree*
Print(){
    Token *t = getToken();
    TokenType tt = t->getType();

    if(tt != T_PRINT){
        pushbacktoken(t);
        return 0;
    }
    delete t;

    PTree *expr = Expr();
    if(!expr){
        cout << "Syntax error on line " << endl;
        return 0;
    }

    t = getToken();
    if(t->getToken() != T_SC){
        cout << "Syntax error on line " << endl;
        delete t;
        return 0;
    }
    return new PTree(PRINT, expr);
}


// assign ::= ID EQUAL expr SC
PTree *
Assign() {
    Token *t = getToke();
    TokenType tt = t->getToken();
    if(tt != T_ID){
        pushbacktoken(t);
        return 0;
        //recheck this, something is missing from here
    }

    t = getToken();
    if(t->getType != T_ID && T_EQUAL){
        cout << "Syntax error on line " << endl;
        return 0;
        delete t;
    }

    string id = t-> getValue();
    delete t;

    Ptree *expr = Expr();
    if(!expr){
        cout << "Syntax error on line " << endl;
        return 0;
    }

    t = getToken();
    if(r->getToken() != T_SC){
        cout << "Syntrax error on line " << endl;
        delete t;
        return 0;
    }
    return new PTree(Assign, expr);
}


// expr ::= term PLUS expr | term MINUS expr | term
PTree *
Expr() {
    Token *t = getToken();
    TokenType tt = t->getType();
    PTree *term  = Term();

    if(!term){
        cout << "Syntax error on line " << endl;
        return 0;
    }
    if(t->getType != T_PLUS && t->getType() != T_MINUS)
        pushbacktoken(t);
        return *term;
    }
    else{
        return Term(l);
        return Expr(r);
    }

    PTree *expr = Term();
    if(!expr){
        cout << "Syntax error on line " << endl;
        return 0;

    }
    delete t;
    return new PTree(expr, term);
}


// term ::= factor STAR term | factor DIV term | factor MOD term | factor
PTree *
Term() {
    Token *t = getToken();
    TokenType tt = t->getType();

    PTree *factor = Factor();

    if(!factor){
        cout << "Syntax error on line " << endl;
        return 0;
    }
    t = getToken();
    if(t->getType() != T_STAR && t->getType() != T_DIV && t->getType != T_MOD){
        pushbacktoken(t);
        return *factor;
    }
    else{
        return Factor(l);
        return Expr(r);
    }

    PTree *term = Term();

    if (!term){
        cout << "Syntax error on line " << endl;
    }
    delete t;

    PTree *factor = Factor();

    if(!factor){
        cout << "Syntax error on line " << endl;
        return 0;
    }

    PTree *factor = Factor();
    if(!factor){
        cout << "Syntax error on line " << endl;
        return 0;
    }
    return new PTree(term);
}

// factor ::= primary STARSTAR factor | primary
PTree *
Factor(){
    Token *t = getToken();
    TokenType tt = t->getType();

    PTree *primary = Primary();
    if(!primary){
        cout << "Syntac error on line " << endl;
        return 0;
    }
    delete t;

    t = getToken();
    if(t->getToke() != T_STARSTAR){
        cout << "Syntax error! " << endl;
    }
    else{
        return Primary(l);
        return Factor(r);
    }

    return new PTree(factor, primary);
}


// primary ::= INTCONST | FLOATCONST | ID | LPAREN expr RPAREN
PTree *
Primary(){
    Token *t = getToken();
    TokenType tt = t->getType();

    if(tt != T-INTCONST && T_FLOATCONST){
        pushbacktoken(t);
        return 0;
    }
    delete t;

    t = getToken();
    if(t->getType() != T_ID){
        cout << "Syntax Error on line " << endl;
        delete t;
        return 0;
    }
    string id = t->getValue();
    delete t;

    of(tt != T_LPAREN && T_RPAREN){
        pusbbacktoken(t);
        return 0;
    }
    delete t;

    PTree *expr = Expr();
    if(!expr){
        cout << "Syntax error on line " << endl;
        return 0;
    }
    delete t;

    return new(primary)
}




9895114/edit

}

这是头文件

extern int linenum;
extern int errcnt;

enum Tokentype {
        T_ERR,
        T_INT,
        T_FLOAT,
        T_PRINT,
        T_SC,
        T_EQUAL,
        T_PLUS,
        T_MINUS,
        T_STAR,
        T_DIV,
        T_MOD,
        T_STARSTAR,
        T_INTCONST,
        T_FLOATCONST,
        T_ID,
        T_LPAREN,
        T_RPAREN,
};

class Token {
        Tokentype       type;
        string          value;
        int             linenum;

public:
        Token(Tokentype t, string v="") {
                type = t;
                value = v;

                linenum = ::linenum;
        }

        Tokentype getType() { return type; }
        string getValue() { return value; }
        int getLinenum() { return linenum; }
};

extern void error(string);
extern int setLexFile(char *);
extern int setLexStdin();
extern Token *getToken();
extern void pushbacktoken( Token * );

我想看看下一个东西是否不是加号或减号标记，然后将其推回并返回返回的术语。例如 expr() 如果它是加号或减号，则使用为左 child 返回的术语，并为右 child 再次调用 Expr()。我为它们编写了功能，但我对它们不太了解，我将它们添加到顶部，有人可以告诉我我的方向是否正确吗？我应该解决什么问题？

// expr ::= term PLUS expr | term MINUS expr | term
    PTree *
    Expr() {
            Token *t = getToken();
            Tokentype tt = t->getType();
            PTree l = left();
            PTree r = right();
            PTree *term  = Term();

            if(!term){
                    cout << "Syntax error on line " << endl;
                    return 0;
            }
            else{
                    if(t->getType() != T_PLUS && t->getType() != T_MINUS){
                            return 0;
                    }
                    else{
                            return left();
                    }
            }

            PTree *expr = Expr();
            if(!expr){
                    cout << "Syntax error on line " << endl;
                    return 0;
            }
            else{
                    if(t->getType() != T_PLUS && t->getType() != T_MINUS){
                            return 0;
            }
            else{
                    return right();
            }
            delete t;
            return new PTree(expr, term);
    }

        // term ::= factor STAR term | factor DIV term | factor MOD term | factor
        PTree *
        Term() {
                Token *t = getToken();
                Tokentype tt = t->getType();
                t = getToken()
                PTree l = left();
                PTree r = right();

                PTree *factor = Factor();
                if(!factor){
                        cout << "Syntax error on line " << endl;
                        return 0;
                }
                else{
                        if(t->getType() != T_STAR && t->getType() != T_DIV && t->getType() != T_MOD){
                                pushbacktoken(t)
                                return 0;
                        }
                        else{
                                return left();
                        }
                }

                PTree *term = Term();
                if (!term){
                        cout << "Syntax error on line " << endl;
                        return 0;
                }
                else{
                        if(t->getType() != T_STAR && t->getType() != T_DIV && t->getType() !=T_MOD){
                                pushbacktoken(t);
                                return 0;
                        }
                        else{
                                return right();
                        }
                }
                return new PTree(term);
        }

    // factor ::= primary STARSTAR factor | primary
    PTree *
    Factor(){
            Token *t = getToken();
            Tokentype tt = t->getType();
            PTree l = left();
            PTree r = right();

            PTree *primary = Primary();
            if(!primary){
                    cout << "Syntac error on line " << endl;
                    return 0;
            }
            else{
                    if(t->getType() != T_STARSTAR){
                            return 0;
                    }
                    else{
                            return left();
                    }
            }

            PTree *factor = Factor();
            if(!factor){
                    cout << "Syntax error on line " << endl;
                    return 0;
            }
            else{
                    if(t->getType() != T_STARSTAR){
                            return 0;
                    }
                    else{
                            return right();
                    }

            return new PTree(factor, primary);
    }

我遇到了这些错误

problem3.cpp: In function ‘PTree* Expr()’:
problem3.cpp:225:17: error: too few arguments to function ‘std::ios_base& std::left(std::ios_base&)’
/usr/include/c++/4.6/bits/ios_base.h:918:3: note: declared here
problem3.cpp:226:18: error: too few arguments to function ‘std::ios_base& std::right(std::ios_base&)’
/usr/include/c++/4.6/bits/ios_base.h:926:3: note: declared here
problem3.cpp:238:16: error: too few arguments to function ‘std::ios_base& std::left(std::ios_base&)’
/usr/include/c++/4.6/bits/ios_base.h:918:3: note: declared here
problem3.cpp:252:16: error: too few arguments to function ‘std::ios_base& std::right(std::ios_base&)’

Answer 1

你有各种各样的错误。大多数源于此:
header 显示 Tokentype，您的代码显示

PTree *
Slist() {
    TokenType tt = t->getType();

C++是区分大小写的，所以你需要把这个改成

PTree *
Slist() {
    Tokentype tt = t->getType();
    //   ^------- lowercase 't'

还有一个错误说

‘class Token’ has no member named ‘getToken’

它确实有一个 getType() 函数 - 也许您打算改为调用它。

另外，对于错误

in ‘t->Token::getType != (Tokentype)14u’

getType 是一个函数，所以你应该调用它

t->Token::getType() != (Tokentype)14u

我相信来自 tthis 行:

if(t->getType() != T_STAR && t->getType() != T_DIV && t->getType != T_MOD)
//                                                             ^^^^

即改成

if(t->getType() != T_STAR && t->getType() != T_DIV && t->getType() != T_MOD)
//                                                             ^^^^

另外，注意你有

Token *t;

在 main 中，所以 Slist 函数看不到它。你可以传递它:

PTree *
Slist(Token *t) {

我怀疑当我们修复您报告的错误时，随着编译器的进一步发展，您会得到更多。尝试阅读消息并修复您理解的内容。