C++ stack malfunctioning?

[HazySmoke)345]

The following code works perfectly:

code:

#include <cstdio> #include <stack> using namespace std; int main(){         int a = 345; stack<int> S;         S.push(a);         printf ("%d", S.top() == a); return 0;}

It makes sense. I pushed the value 345 into a stack and compared that value immediately to a.

The following code, even though it's very similar to above, doesn't work:

code:

#include <cstdio> #include <stack> using namespace std; typedef struct{int x, y;}point; int main(){         point p; stack<point> S;         p.x = 345; p.y = -345;         S.push(p);         printf ("%d", S.top() == p); return 0;}

The error says:
testing.cpp:9: error: no match for 'operator==' in '(&S)->std::stack<_Tp, _Sequence>::top [with _Tp = point, _Sequence = std::deque<point, std::allocator<point> >]() == p'

I totally don't get it. Why does the stack.top() method work for one integer but not for a collection of two?

[Mazer]

Have you tried defining the == operator for your new structure? I could be wrong, but I don't think it's supposed to provide one by default.

[OneOffDriveByPoster]

Mazer @ Sat Sep 15, 2007 12:30 pm wrote:

Have you tried defining the == operator for your new structure? I could be wrong, but I don't think it's supposed to provide one by default.

Try std::pair<int, int> (#include <utility>)--it's great.

[md]

IIRC the compiler will generate a compare function for any user defined types. What exactly does std::stack<>::top() return? Perhaps it's not returning what you think...

What's wrong with

c++:

struct point { int x, y; };

There is nothing I hate more then needless typedefs.

[wtd]

Using std::pair<T> would be the better option.