error:no type named iterator_category in struct

又一個非常非常詭異的一個編譯錯誤。當我第一次遇到這個錯誤的時候頭都暈了。還是先把代碼貼上來吧：

#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;

typedef struct TagPoint
{
    int x, y;
}Point;

inline double distance(const Point& a, const Point& b)
{
    return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y));
}

int main(int argc, char **argv)
{
    Point a, b;
    printf(”%lf\n”, distance(a, b));
    return 0;
}

#include <iostream>

#include <stdio.h> #include <math.h> using namespace std; typedef struct TagPoint { int x, y; }Point; inline double distance(const Point& a, const Point& b) { return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y)); } int main(int argc, char **argv) { Point a, b; printf("%lf\n", distance(a, b)); return 0; }

問題出在哪裏呢？我們只是寫了一段普通的代碼，卻爆出來一大堆STL相關的錯誤信息（STL的錯誤信息實在是太難看了）。後來仔細研究發現，是函數命名存在問題。猛然想起distance是STL中求迭代器距離的一個函數，這裏衝突了。按理來說編譯器應該可以推斷出使用哪個函數吧～～也曾經遇到過類似的編譯錯誤，有關transform函數的。

好啦，解決就是給distance換一個名字。附上編譯錯誤信息：

C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h: In instantiation of `std::iterator_traits':
test.cpp:19:   instantiated from here
C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h:129: error: no type named `iterator_category' in `struct Ta
gPoint'
C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h:130: error: no type named `value_type' in `struct TagPoint'

C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h:131: error: no type named `difference_type' in `struct TagP
oint'
C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h:132: error: no type named `pointer' in `struct TagPoint'
C:/Dev-Cpp/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_i
terator_base_types.h:133: error: no type named `reference' in `struct TagPoint'