【STL源码剖析】--error: ‘power’ was not declared in this scope

#include <numeric>
#include <vector>
#include <iterator>
#include <iostream>
using namespace std;

int main(int argc, char **argv)
{
	int iArray[5] = {1, 2, 3, 4, 5};

	vector<int> iVect(iArray, iArray+5);

	cout << accumulate(iVect.begin(), iVect.end(), 0) << endl;
	cout << accumulate(iVect.begin(), iVect.end(), 0, minus<int>()) << endl;

	cout << inner_product(iVect.begin(), iVect.end(), iVect.begin(), 10) << endl;
	cout << inner_product(iVect.begin(), iVect.end(), iVect.begin(), 10, minus<int>(), plus<int>()) << endl;

	ostream_iterator<int> oIter(cout, " ");
	partial_sum(iVect.begin(), iVect.end(), oIter);
	cout << endl;
	partial_sum(iVect.begin(), iVect.end(), oIter, minus<int>());
	cout << endl;

	adjacent_difference(iVect.begin(), iVect.end(), oIter);
	//1 1 1 1 1(#1元素照录, #n新元素等于 #n 旧元素 - #n-1 旧元素 )
	cout << endl;

	adjacent_difference(iVect.begin(), iVect.end(), oIter, plus<int>());
	//1 3 5 7 9(#1元素照录, #n新元素等于 op(#n 旧元素, #n-1 旧元素) )
	cout << endl;

	cout << power(10, 3) << endl;	///usr/lib/gcc/i686-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ext/numeric中有
	cout << power(10, 3, plus<int>()) << endl;

	int n = 3;
	iota(iVect.begin(), iVect.end(), n);

	for(int i = 0; i < iVect.size(); i++) {
		cout << iVect[i] << " ";
	}
	cout << endl;
}

编译报错：

主要原因：

虽然GCC编译器完美集成了SGI STL，但是在使用GCC编译器编译使用SGI STL的源码时，需要注意：如iota、power等函数是非C++标准的函数，是SGI专属的函数，对于这类函数需要修改包含的头文件，这类头文件一般位于ext目录下，例如：numeric头文件位于/usr/lib/gcc/i686-redhat-linux/4.4.6/../../../../include/c++/4.4.6/目录下，而扩展的numeric则位于/usr/lib/gcc/i686-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ext/目录下。因此，上述代码的头文件改为：

#include <ext/numeric>		//For iota, already #include <numeric>
#include <vector>
#include <iterator>
#include <iostream>
using namespace std;
using namespace __gnu_cxx;	//For power iota

特别注意：using namespace __gnu_cxx;不可少，因为头文件/usr/lib/gcc/i686-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ext/numeric中有一句_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)，需要使用__gnu_cxx命名空间。

正确代码：

//#include <ext/functional> 	// For identity_element
#include <ext/numeric>		//For iota, already #include <numeric>
#include <vector>
#include <iterator>
#include <iostream>
using namespace std;
using namespace __gnu_cxx;	//For power iota

int main(int argc, char **argv)
{
	int iArray[5] = {1, 2, 3, 4, 5};

	vector<int> iVect(iArray, iArray+5);

	cout << accumulate(iVect.begin(), iVect.end(), 0) << endl;
	cout << accumulate(iVect.begin(), iVect.end(), 0, minus<int>()) << endl;

	cout << inner_product(iVect.begin(), iVect.end(), iVect.begin(), 10) << endl;
	cout << inner_product(iVect.begin(), iVect.end(), iVect.begin(), 10, minus<int>(), plus<int>()) << endl;

	ostream_iterator<int> oIter(cout, " ");
	partial_sum(iVect.begin(), iVect.end(), oIter);
	cout << endl;
	partial_sum(iVect.begin(), iVect.end(), oIter, minus<int>());
	cout << endl;

	adjacent_difference(iVect.begin(), iVect.end(), oIter);
	//1 1 1 1 1(#1元素照录, #n新元素等于 #n 旧元素 - #n-1 旧元素 )
	cout << endl;

	adjacent_difference(iVect.begin(), iVect.end(), oIter, plus<int>());
	//1 3 5 7 9(#1元素照录, #n新元素等于 op(#n 旧元素, #n-1 旧元素) )
	cout << endl;

	cout << power(10, 3) << endl;	///usr/lib/gcc/i686-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ext/numeric中
	cout << power(10, 3, plus<int>()) << endl;

	int n = 3;
	iota(iVect.begin(), iVect.end(), n);

	for(int i = 0; i < iVect.size(); i++) {
		cout << iVect[i] << " ";
	}
	cout << endl;
}

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