Question

下述C++代码是两年前用10.1%的含水层机器汇编的。

#ifndef DATA_H
#define DATA_H
#include <iostream>
#include <iomanip>


inline double sqr(double x) { return x*x; }
enum   Direction { X,Y,Z };

inline Direction next(const Direction d)
{
  switch(d)
  {
  case X: return Y;
  case Y: return Z;
  case Z: return X;
  }
}

inline ostream& operator<<(ostream& os,const Direction d)
{
  switch(d)
  {
  case X: return os << "X";
  case Y: return os << "Y";
  case Z: return os << "Z";
  }
}
...
...

现在,我正试图将其编入乌班图9.10,我犯了错误:

data.h:20: error: expected initializer before ‘&’ token

参见:

inline ostream& operator<<(ostream& os,const Direction d)

该机器使用的g++是:

Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion= Ubuntu 4.4.1-4ubuntu9  --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9)

各位能否让我对这一错误表示某种担忧?

增编

P.D. 如果是这样的话,我就犯了错误:

data.h:20: error: declaration of ‘operator<<’ as non-function
data.h:20: error: ‘ostream’ was not declared in this scope
data.h:20: error: ‘os’ was not declared in this scope
data.h:20: error: expected primary-expression before ‘const’

Answer 1

作为C++标准图书馆的所有内容,ostream 载于std 名称space, so it s std:ostream。

我认为,如果用于汇编,那就是错误的。

Answer 2

www.un.org/Depts/DGACM/index_french.htm 班级是C++标准游览图书馆的一部分,在名称空间上界定:<代码>std。

so you probably should add std:: before ostream
or

using namespace std;

但是,正如评论之一所述:

You should never use using namespace std in a header as it can propagate to other files.

Answer 3

页: 1

inline Direction next(const Direction d)
{
   switch(d)
   {
     case X: return Y;
     case Y: return Z;
     case Z: return X;
   }
}**;**//missing semicolon

inline ostream& operator<<(ostream& os,const Direction d)
{
  switch(d)
  {
     case X: return os << "X";
     case Y: return os << "Y";
     case Z: return os << "Z";
  }
}`

Answer 4

页: 1 此外,你应当把指示作为参考(尽管在这种情况下,它赢得了一定伤害):

inline std::ostream& operator<<(std::ostream& os,const Direction& d)

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