[求助]stl sort中的谓词参数 - C++教室 - C++论坛

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[求助]stl sort中的谓词参数

sort中第三个参数是个函数指针，返回类型bool，接受两个元素对象。

我想知道其完整的定义类型

bool (*pred) (****,****);

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第 2 楼

回复：（aipb2007）[求助]stl sort中的谓词参数

don't know if i understand what you need.

The predicate (I don't know if it should be translated as "weici") can be a funtion pointer and function object --- a class which overloads operator().

Here is what I copied from cplusplus.com

程序代码：

// sort algorithm example #include <iostream> #include <algorithm> #include <vector> using namespace std; bool myfunction (int i,int j) { return (i<j); } struct myclass { bool operator() (int i,int j) { return (i<j);} } myobject; int main () { int myints[] = {32,71,12,45,26,80,53,33}; vector<int> myvector (myints, myints+8); // 32 71 12 45 26 80 53 33 vector<int>::iterator it; // using default comparison (operator <): sort (myvector.begin(), myvector.begin()+4); //(12 32 45 71)26 80 53 33 // using function as comp sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80) // using object as comp sort (myvector.begin(), myvector.end(), myobject); //(12 26 32 33 45 53 71 80) // print out content: cout << "myvector contains:"; for (it=myvector.begin(); it!=myvector.end(); ++it) cout << " " << *it; cout << endl; return 0; }

I am working on a system which has no Chinese input. Please don\'t blame me for typing English.

第 3 楼

oh,I made a unclear expression.

my problem is:

template<class T>
struct X{
typedef bool (*pred)(const T&,const T&); //define a function pointer type
pred p; //pred data member
X(pred _p):p(_p){}
};
bool cmp1(int a,int b){return a<b;}
bool cmp2(const int &a,const int &b){return a<b;}
X<int> x1(cmp1); //doesn't work,compile error
X<int> x2(cmp2); //ok

how I define the type of pred can accept both cmp1 and cmp2?
or maybe I should use the sort(1,2,pred)'s way to implement,because both sort(..,..,cmp1) and sort(..,..,cmp2)
can be accepted,but I don't konw the sort's implementation clearly.

[此贴子已经被作者于2007-10-14 15:19:17编辑过]

Ｆight ｔｏｗin or ｄie...

第 4 楼

why don't you refer stl source code?

马马乎乎

第 5 楼

我进入了外语世界

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