编译通不过？？？？？？

zq97_0

#include <iostream>
#include <math.h>

using namespace std;

int main (int argc, char *argv[])
{
        struct complex val =  {4.0, 2.0};
        double result = cabs (val);
        cout << "result = " << result << endl;

        return 0;
}
g++ 4.0.3
temp.cpp: In function ‘int main(int, char**)’:
temp.cpp:8: error: variable ‘complex val’ has initializer but incomplete type
temp.cpp:9: error: ‘cabs’ was not declared in this scope