Question

我在尝试从文本文件中读取输入时遇到问题，最初程序通过cin从控制台获取输入，但需要将其更改为从文本文件中读取输入。如果它不依赖多个类来获取输入，那似乎很容易。我尝试过创建一个包含以下内容的globals.h文件：

 #include <iostream>
 #include <string>
 #include <vector>
 #include <sstream>
 #include <string>
 #include <fstream>

 extern std::ifstream input;

然后是globals.cpp

 #include <iostream>
 #include <string>
 #include <vector>
 #include <sstream>
 #include <string>
 #include <fstream>

 std::fstream input("C:\\Users\\ricky\\CLionProjects\\module3\\input.txt");

这里是我的main.cpp文件，我相信它可以在这个文件中运行，但是因为我有其他类需要读取输入，我收到链接错误

 #include <iostream>
 #include <string>
 #include <vector>
 #include <sstream>
 #include <string>
 #include <fstream>

 using namespace std;

 #include "expression.h"
 #include "subexpression.h"
 #include "symboltable.h"
 #include "parse.h"
 #include "globals.h"

 SymbolTable symbolTable;

 void parseAssignments();



 int main()
 {

    input.open("C:\\Users\\ricky\\CLionProjects\\module3\\input.txt");





for( std::string line; getline( input, line ); )
{
    cout << "\n";
    cout << "Working on line: " << line << endl;
    Expression* expression;
    char paren, comma;
    cout << "Read in expression: ";
    input >> paren;

    expression = SubExpression::parse();
    input >> comma;
    parseAssignments();
    cout << "Value = " << expression->evaluate() << endl;
     }


     return 0;
 }

下面的operand.cpp ......

 #include <cctype>
 #include <iostream>
 #include <list>
 #include <string>

 using namespace std;

 #include "expression.h"
 #include "subexpression.h"
 #include "operand.h"
 #include "variable.h"
 #include "literal.h"
 #include "parse.h"
 #include "globals.h"

 #include <fstream>


 Expression* Operand::parse()
 {
     char paren;
     double value;

     input >> ws;
     if (isdigit( input.peek()))
     {
         input >> value;
         Expression* literal = new Literal(value);
         return literal;
     }
     if ( input.peek() == '(')
     {
         input >> paren;
         return SubExpression::parse();
     }
     else
         return new Variable(parseName());
     return 0;
 }

这是我收到的错误：

LINK Pass 1: command "C:\PROGRA~2\MICROS~3\2017\COMMUN~1\VC\Tools\MSVC\1413~1.261\bin\Hostx86\x86\link.exe /nologo @CMakeFiles\module3.dir\objects1.rsp /out:module3.exe /implib:module3.lib /pdb:C:\Users\ricky\CLionProjects\module3\cmake-build-debug\module3.pdb /version:0.0 /machine:X86 /debug /INCREMENTAL /subsystem:console kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:CMakeFiles\module3.dir/intermediate.manifest CMakeFiles\module3.dir/manifest.res" failed (exit code 1120) with the following output:
main.cpp.obj : error LNK2001: unresolved external symbol "class std::basic_ifstream<char,struct std::char_traits<char> > input" (?input@@3V?$basic_ifstream@DU?$char_traits@D@std@@@std@@A)
Operand.cpp.obj : error LNK2001: unresolved external symbol "class std::basic_ifstream<char,struct std::char_traits<char> > input" (?input@@3V?$basic_ifstream@DU?$char_traits@D@std@@@std@@A)
Parse.cpp.obj : error LNK2001: unresolved external symbol "class std::basic_ifstream<char,struct std::char_traits<char> > input" (?input@@3V?$basic_ifstream@DU?$char_traits@D@std@@@std@@A)
Subexpression.cpp.obj : error LNK2001: unresolved external symbol "class std::basic_ifstream<char,struct std::char_traits<char> > input" (?input@@3V?$basic_ifstream@DU?$char_traits@D@std@@@std@@A)
module3.exe : fatal error LNK1120: 1 unresolved externals
NMAKE : fatal error U1077: '"C:\Program Files\JetBrains\CLion 2018.1.2\bin\cmake\bin\cmake.exe"' : return code '0xffffffff'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.13.26128\bin\HostX86\x86\nmake.exe"' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.13.26128\bin\HostX86\x86\nmake.exe"' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.13.26128\bin\HostX86\x86\nmake.exe"' : return code '0x2'
Stop.

从文本文件C ++问题

0 个答案: