error:no type named iterator_category in struct

又一个非常非常诡异的一个编译错误。当我第一次遇到这个错误的时候头都晕了。还是先把代码贴上来吧：

#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; }

问题出在哪里呢？我们只是写了一段普通的代码，却爆出来一大堆STL相关的错误信息（STL的错误信息实在是太难看了）。后来仔细研究发现，是函数命名存在问题。猛然想起distance是STL中求迭代器距离的一个函数，这里冲突了。按理来说编译器应该可以推断出使用哪个函数吧～～也曾经遇到过类似的编译错误，有关transform函数的。

好啦，解决就是给distance换一个名字。附上编译错误信息：

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'