有关size_t的问题

Question

如果你进入我的帖子历史,你会发现我正在尝试为我正在研究的语言开发一个翻译.我想使用size_t使用两个不同的代码,但它们都没有返回任何内容.

这是我正在尝试的帖子:http://stackoverflow.com/questions/1215688/read-something-after-a-word-in-c

当我尝试使用我正在测试的文件时,它什么都不返回.这是示例文件(只是我试图用我的语言开发的打印函数):

print "This is a print function that i'm trying to develop in my language"

但请记住,这就像在Python中打印一样,用户输入引号("")是什么必须打印到所有人,请记住,用户可以选择放入引号的内容,然后不要像简单的cout,发布读取引号内部的内容并将其打印到所有内容.但是这里有两个测试代码可以执行此操作,但是它们都没有返回给我:

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
using namespace std;
int main( int argc, char* argv[] )
{
    // Error Messages
    string extension = argv[ 1 ];

    if(argc != 2)
    {
       cout << "Error syntax is incorrect!\nSyntax: " << argv[ 0 ] << " <file>\n";
      return 0;
    }
    if(extension[extension.length()-3] != '.')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    if(extension[extension.length()-2] != 't')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    if(extension[extension.length()-1] != 'r')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    // End of the error messages

    ifstream file(argv[ 1 ]);
    if (!file.good()) {
       cout << "File " << argv[1] << " does not exist.\n";
      return 0;
    }
    string linha;
    while (!file.eof())
    {
    getline(file, linha);
    if (linha == "print")
       {
          size_t idx = linha.find("\""); //find the first quote on the line
          while ( idx != string::npos ) {
             size_t idx_end = linha.find("\"",idx+1); //end of quote
             string quotes;
             quotes.assign(linha,idx,idx_end-idx+1);
             // do not print the start and end " strings
             cout << "quotes:" << quotes.substr(1,quotes.length()-2) << endl;
             //check for another quote on the same line
             idx = linha.find("\"",idx_end+1); 
          } 
       }
    }
  return 0;
}

第二:

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
using namespace std;
int main( int argc, char* argv[] )
{
    // Error Messages
    string extension = argv[ 1 ];

    if(argc != 2)
    {
       cout << "Error syntax is incorrect!\nSyntax: " << argv[ 0 ] << " <file>\n";
      return 0;
    }
    if(extension[extension.length()-3] != '.')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    if(extension[extension.length()-2] != 't')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    if(extension[extension.length()-1] != 'r')
    {
       cout << "Extension not valid!" << endl;
       cout << "Default extension *.tr" << endl;
      return 0;
    }
    // End of the error messages

    ifstream file(argv[ 1 ]);
    if (!file.good()) {
       cout << "File " << argv[1] << " does not exist.\n";
      return 0;
    }
    string linha;
    while (!file.eof())
    {
    getline(file, linha);
    if (linha == "print")
       {
          string code = " print \" hi \" ";
          size_t beg = code.find("\"");
          size_t end = code.find("\"", beg+1);
          // end-beg-1 = the length of the string between ""
          cout << code.substr(beg+1, end-beg-1);
       }
    }
  return 0;
}

以下是控制台中打印的内容:

ubuntu@ubuntu-laptop:~/Desktop/Tree$ ./tree test.tr
ubuntu@ubuntu-laptop:~/Desktop/Tree$

就像我说的,它没有打印任何东西. 请参阅DIC中的帖子:http://www.dreamincode.net/forums/showtopic118026.htm

谢谢Nathan Paulino Campos

Answer 1

你的问题就在于此

if (linha == "print")

假设刚刚读入的整行是"打印",而不是带有打印的行STARTS.

另外,为什么要对.tr扩展名使用3个单独的检查,而只是检查".tr"文件名的结尾？(在检查子字符串之前,您还应该检查argv [1]是否足够长...)