ostringstream 运算符<<很长时间？

发布于 2024-12-01 18:21:30 字数 1222 浏览 0 评论 0 原文

$ uname -a
Darwin Wheelie-Cyberman 10.8.0 Darwin Kernel Version 10.8.0: Tue Jun  7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386

$ g++ --version
i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5666) (dot 3)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cat nolove.cc
#include <iostream>
#include <sstream>

using namespace std;

int main(int argc, char ** argv) {
  unsigned long long i = 0;
  ostringstream o();

  // Compiles fine
  cout << i;

  // Explodes, see below
  o << i;

  return 0;
}

$ g++ -o nolove nolove.cc
nolove.cc: In function ‘int main(int, char**)’:
nolove.cc:14: error: invalid operands of types ‘std::ostringstream ()()’ and ‘long long unsigned int’ to binary ‘operator<<’

我对 C++ 有点陌生（但对编程或面向对象设计等不熟悉），所以我假设我只是做错了。实际上，上面的 unsigned long long 相当于我的目标平台上的无符号 64 位整数（上面和 linux 2.6 上的 g++ 4.4.1），相当于相同事物的不同类型也是可以接受的（但我还没有找到任何.)

我可以使用 ostringstream 来格式化此（或类似）类型吗？如果没有，我可以在不拖入 stdio 和 snprintf 的情况下完成吗？从更哲学的角度来说，cout 可以执行的类型是如何实现的，以及为什么该功能没有扩展到字符串流内容？

原文

$ uname -a
Darwin Wheelie-Cyberman 10.8.0 Darwin Kernel Version 10.8.0: Tue Jun  7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386

$ g++ --version
i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5666) (dot 3)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cat nolove.cc
#include <iostream>
#include <sstream>

using namespace std;

int main(int argc, char ** argv) {
  unsigned long long i = 0;
  ostringstream o();

  // Compiles fine
  cout << i;

  // Explodes, see below
  o << i;

  return 0;
}

$ g++ -o nolove nolove.cc
nolove.cc: In function ‘int main(int, char**)’:
nolove.cc:14: error: invalid operands of types ‘std::ostringstream ()()’ and ‘long long unsigned int’ to binary ‘operator<<’

I'm somewhat new to C++ (but not to programming or OO design, etc) so I'm assuming I'm just doing it wrong. In practice the unsigned long long above equates to an unsigned 64bit integer on my targeted platforms (above and g++ 4.4.1 on linux 2.6), a different type that amounted to the same thing would also be acceptable (but I haven't found any.)

Can I use an ostringstream to format this (or similar) type? If not, can I do it without dragging in stdio and snprintf? More philosophically, how does the typing work out that cout can do it, and why wasn't that functionality extended to the string stream stuff?

分享到QQ

分享到微博