Question

因此，我要将自定义语言解释器从Java转换为C ++，并且无法设置Token类型的currentToken成员。

tokens.hpp

#include <iostream>

class Token {
    public:
        std::string type;
        Token(std::string newType);
};

class IntegerToken:public Token {
    public:
        int value;
        IntegerToken(int newValue):Token("INTEGER") {
            value = newValue;
        };
};

class MinusToken:public Token {
    public:
        std::string value;
        MinusToken():Token("OP") {
            value = "-";
        };
};

class PlusToken:public Token {
    public:
        std::string value;
        PlusToken():Token("OP") {
            value = "+";
        };
};

class EOLToken:public Token {
    public:
        EOLToken():Token("NEWLINE"){};
};

tokens.cpp

#include "tokens.hpp"

Token::Token(std::string newType) {
    type = newType;
}

int main() {
    return 0;
}

BeanLexxer.hpp

#include <iostream>
#include "tokens.hpp"


class BeanLexxer {
    std::string line;
    int pos;
    Token currentToken;
    char currentChar;

    bool isSpace(char c);
    bool isDigit(char c);
    void advance();
    void skipWhitespace();
    int getInteger();
    void eat();
    Token getNextToken();
    void run();

    public:
        BeanLexxer(std::string newLine);
};

BeanLexxer.cpp

#include <iostream>
#include "BeanLexxer.hpp"

bool BeanLexxer::isSpace(char c) {
    return c == ' ';
}

bool BeanLexxer::isDigit(char c) {
    return (c > 64 & c < 91) || (c > 96 && c < 123);
}

void BeanLexxer::advance() {
    pos++;
    if (pos > line.length() - 1) {
        currentChar = 0;
    } else {
        currentChar = line[pos];
    }
}

void BeanLexxer::skipWhitespace() {
    while (currentChar != 0 && isSpace(currentChar)) {
        advance();
    }
}

int BeanLexxer::getInteger() {
    std::string result = "";
    while (currentChar != 0 && isDigit(currentChar)) {
        result += currentChar;
        advance();
    }
    return std::stoi(result);
}

void BeanLexxer::eat() {
    currentToken = getNextToken();
}

Token BeanLexxer::getNextToken() {
    while (currentChar != 0) {
        if (currentChar == ' ') {
            skipWhitespace();
            continue;
        }

        if (isDigit(currentChar)) {
            return IntegerToken(getInteger());
        }

        if (currentChar == '+') {
            advance();
            return PlusToken();
        }

        if (currentChar == '-') {
            advance();
            return MinusToken();
        }
    }
    return EOLToken();
}

void BeanLexxer::run() {
    eat();

    while ((currentToken.type).compare("NEWLINE") != 0) {
        std::cout << currentToken.type << "\n";
        eat();
    }
    std::cout << currentToken.type << "\n";
}

BeanLexxer::BeanLexxer(std::string newLine) {
    line = newLine;
    pos = 0;
    currentChar = line[pos];
    currentToken = EOLToken();
}

int main() {
    return 0;
}

Runner程序（BeanInterpreter.cpp）

#include <iostream>
#include "BeanLexxer.hpp"

int main() {
    BeanLexxer lexxer = BeanLexxer("3+45-6");

    return 0;
}

Geany说该错误出在BeanLexxer.cpp的构造函数中，我必须显式初始化currentToken。我知道这意味着令牌currentToken（“ NULL”）;，我认为可以做的唯一地方是.hpp，但这也带来了错误。它与我的类继承设置有关系吗，或者我还缺少其他东西？错误：

g++ -Wall -o "BeanLexxer" "BeanLexxer.cpp" (in directory: /Users/Splavacado100/Desktop/Coding/VAULT/Bean-C++)
BeanLexxer.cpp:74:13: error: constructor for 'BeanLexxer' must explicitly initialize the member 'currentToken' which does not have a default constructor
BeanLexxer::BeanLexxer(std::string newLine) {
            ^
./BeanLexxer.hpp:8:8: note: member is declared here
        Token currentToken;
              ^
./tokens.hpp:3:7: note: 'Token' declared here
class Token {
      ^
1 error generated.
Compilation failed.

Token类类型的C ++类成员不会初始化

0 个答案: