对对象列表进行排序 [英] Sorting a list of objects
问题描述
你好，
我正在完成一个语音识别点唱机
（ http://intelligentjukebox.com/ ）我有一个非常基本的模板
问题。我找不到任何我想做的好例子。我可以用比b ++模板库中的例子更好的方式编写自己的排序函数。
有人能告诉我如何定义<运算符所以我可以使用
排序函数作为列表模板。我想用m_filename按照
az（降序）顺序对Song对象进行排序。
谢谢
这是我的代码：
// ------------------------------------- -----------------------------------------
class Song
{
public：
Album * m_pAlbum; //轻松获取专辑
string m_name; //显示名称
string m_filename;
};
list< Song *> * pSongsList; //保存这张专辑的所有歌曲
// --------------------------- -------------------------------------------------- -
我希望这个函数调用工作：
pSongsList-> sort（）;
Hello,
I''m finishing a speech recognition jukebox
(http://intelligentjukebox.com/) I have a very basic template
question. I can''t find any good examples of what I want to do. I
could write my own sort function faster than I could find a good
reference with examples on the c++ template library.
Can someone tell me how to define the "<" operator so I can use the
sort function for the list template. I want to sort Song objects in
a-z (descending) order by m_filename.
thanks
Here is my code:
//------------------------------------------------------------------------------
class Song
{
public:
Album* m_pAlbum; // make it easy to get the album
string m_name; //display name
string m_filename;
};
list<Song*> *pSongsList; // holds all the songs for this album
//------------------------------------------------------------------------------
I want to this function call to work:
pSongsList->sort();
推荐答案
Jeff写道：
Jeff wrote:
你好，
我正在完成一次语音识别自动点唱机
（ http://intelligentjukebox.com/ ）我有一个非常基本的模板
问题。我找不到任何我想做的好例子。我可以更快地编写自己的排序函数，而不是在c ++模板库中找到一个很好的参考资料。
有人可以告诉我如何定义< ;"运算符，所以我可以使用
排序函数的列表模板。我想用m_filename按照z / az（降序）顺序对Song对象进行排序。
谢谢
这是我的代码：
// --- -------------------------------------------------- -------------------------
班级歌曲
{
公开：
专辑* m_pAlbum; //轻松获取专辑
string m_name; //显示名称
字符串m_filename;
};
list< Song *> * pSongsList; //保存这张专辑的所有歌曲
// ------------------------------- -----------------------------------------------
我希望这个函数调用工作：
pSongsList-> sort（）;
Hello,
I''m finishing a speech recognition jukebox
(http://intelligentjukebox.com/) I have a very basic template
question. I can''t find any good examples of what I want to do. I
could write my own sort function faster than I could find a good
reference with examples on the c++ template library.
Can someone tell me how to define the "<" operator so I can use the
sort function for the list template. I want to sort Song objects in
a-z (descending) order by m_filename.
thanks
Here is my code:
//------------------------------------------------------------------------------
class Song
{
public:
Album* m_pAlbum; // make it easy to get the album
string m_name; //display name
string m_filename;
};
list<Song*> *pSongsList; // holds all the songs for this album
//------------------------------------------------------------------------------
I want to this function call to work:
pSongsList->sort();
你可以'' t，因为该函数调用将使用运算符<在元素上
类型，它是指向Song的指针。你不能改变
指针的内置行为，因此你不能重载那个运算符<。
你可以做的是指定另一种比较：
< br $>
struct song_cmp
{
bool operator（）（Song * lhs，Song * rhs）const
{
返回lhs-> m_filename< rhs-> m_filename;
}
};
pSongList.sort（song_cmp（））;
You can''t, because that function call would use operator< on the element
type, which is pointer to Song. You cannot change the built-in behavior of
pointers, therefore you cannot overload that operator<.
What you can do is specify an alternative comparison:
struct song_cmp
{
bool operator()(Song* lhs, Song* rhs) const
{
return lhs->m_filename < rhs->m_filename;
}
};
pSongList.sort(song_cmp());
2005年8月17日星期三01:06:13 +0200，Rolf Magnus< ra ****** @ t-online.de>
写道：
On Wed, 17 Aug 2005 01:06:13 +0200, Rolf Magnus <ra******@t-online.de>
wrote:
你不能，因为该函数调用将使用运算符<在元素
类型，这是指向宋的指针。你不能改变
指针的内置行为，因此你不能重载那个运算符<。
你可以做的是指定另一种比较：
struct song_cmp {
bool operator（）（Song * lhs，Song * rhs）const
{
返回lhs-> m_filename< rhs-> m_filename;
}
};
pSongList.sort（song_cmp（））;
You can''t, because that function call would use operator< on the element
type, which is pointer to Song. You cannot change the built-in behavior of
pointers, therefore you cannot overload that operator<.
What you can do is specify an alternative comparison:
struct song_cmp
{
bool operator()(Song* lhs, Song* rhs) const
{
return lhs->m_filename < rhs->m_filename;
}
};
pSongList.sort(song_cmp());
我正在使用VC ++ 6.0。你能告诉我如何编译吗？
谢谢
----------------------- --------
第95行：
m_pSongsList-> sort（song_cmp（））;
编译......
music.cpp
J：\ home \ jeff\src\intelligent_jukebox\dev\intellimu sic \current\music.cpp（95 ）
：错误C2664：''void __thiscall std :: list< class Song *，class
std :: allocator< class Song *> > :: sort（struct std :: greater< class Song
*>）''：无法将参数1从''
ct song_cmp''转换为''struct std :: greater< class Song *>''
没有构造函数可以采用源类型或构造函数
重载决策是不明确的
I''m using VC++ 6.0. Can you tell me how to make this compile?
thanks
-------------------------------
line 95:
m_pSongsList->sort(song_cmp());
Compiling...
music.cpp
J:\home\jeff\src\intelligent_jukebox\dev\intellimu sic\current\music.cpp(95)
: error C2664: ''void __thiscall std::list<class Song *,class
std::allocator<class Song *> >::sort(struct std::greater<class Song
*>)'' : cannot convert parameter 1 from ''stru
ct song_cmp'' to ''struct std::greater<class Song *>''
No constructor could take the source type, or constructor
overload resolution was ambiguous
在五分钟内，我写了一个冒泡排序，它为我的节目启动时间增加了不到1/10
秒的14,000首歌曲。大多数
专辑的歌曲少于20首。
我花了两个多小时试图找出延迟的乐谱
to排序列表并失败。显然没有明确的例子
如何使用您自己的比较函数对列表进行排序。有时我
真的很讨厌c ++。
感谢你的帮助，尽管
int n;
bool bSorted = false;
Song * tmpSong;
while（false == bSorted）
{
bSorted = true;
for（n = 0; n< m_totalSongs-1; n ++）
{
如果（（m_pSongsArray [N]） - > m_filename>
（m_pSongsArray [N + 1]） - > m_filename）
{
//交换值
tmpSong = m_pSongsArray [N];
m_pSongsArray [N] = m_pSongsArray [N + 1];
m_pSongsArray [n + 1] = tmpSong;
bSorted = false;
}
}
} / /结束时
In five minutes I wrote a bubble sort which added less than 1/10 of a
second to the startup time of my program for 14,000 songs. Most
albums have less than 20 songs.
I spent more than two hours trying to figure out the retarded notation
to sort a list and failed. Apparently there are no clear examples of
how to sort a list using your own comparison function. Sometimes I
really hate c++.
thanks for the help anyway though
int n;
bool bSorted = false;
Song* tmpSong;
while (false == bSorted)
{
bSorted = true;
for (n = 0; n < m_totalSongs-1; n++)
{
if ( (m_pSongsArray[n])->m_filename >
(m_pSongsArray[n+1])->m_filename )
{
// swap values
tmpSong = m_pSongsArray[n];
m_pSongsArray[n] = m_pSongsArray[n+1];
m_pSongsArray[n+1] = tmpSong;
bSorted = false;
}
}
} // end while
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