Thread: adding an #include stops my program from compiling

hi,

I'm working on some assignment for school.
Thanks to some previous help on this board I already finished the basics.
Now I am writing the more complex stuff. I tried compiling what I wrote so far but I started getting a lot of errors from my compiler.
when I tried commenting out all the new parts I saw that just by adding 1 #include statement I got those error messages.
I really cant figure out what is happening.

here is the crashing code:

Code:

#ifndef SCHEDULEITEM_H
#define SCHEDULEITEM_H

#include <iostream>
#include <string>
#include "schedule.h"

typedef unsigned long int ulint;

class ScheduleItem
{   public:
        friend bool Schedule::check_item(ScheduleItem&, const ScheduleItem&, ScheduleItem&);
        ScheduleItem(ulint, ulint, std::string);
        ScheduleItem(std::istream&);
        ulint getbegin() const;
        ulint getend() const;
        std::string getdescription() const;
        ulint getlength() const;
    private:
        ulint begin_;
        ulint end_;
        std::string descr_;
};

std::ostream& operator<<(std::ostream&, const ScheduleItem&);

bool operator<(const ScheduleItem&, const ScheduleItem&);
bool operator>(const ScheduleItem&, const ScheduleItem&);
bool operator==(const ScheduleItem&, const ScheduleItem&);

#endif

by commenting out the bold #include (and also the bold friend-function, because it needs stuff that gets included by the #include)
everything works fine (well, fine meaning: program compiles)

schedule.h also gets included from other files so I dont believe there is something wrong with that, but I'll show it below just to be sure.

Code:

// schedule.h

#ifndef SCHEDULE_H
#define SCHEDULE_H

#include <iostream>
#include <list>
#include "scheduleitem.h"

typedef unsigned long int ulint;

class Schedule
{   public:
        friend std::ostream& operator<<(std::ostream&, const Schedule&);
        Schedule();
        Schedule(std::istream&);
        bool insert_item(const ScheduleItem&);
        bool remove_item(const ScheduleItem&);
        bool check_item(ScheduleItem&, const ScheduleItem&, ScheduleItem&);
        bool check_item(ScheduleItem&, const ScheduleItem&, ScheduleItem&, const std::list<Schedule>&);
    private:
        std::list<ScheduleItem> items_;
};

#endif

I'll also show you the Schedule::check_item code, but commenting this part out still gives the same error messages so I dont think it has anything to do with that (although there might be some mistakes in the code, but I havent been able to find that out yet because of these errors).

Code:

// part of schedule.cc

bool Schedule::check_item(ScheduleItem& sibefore, const ScheduleItem& si, ScheduleItem& siafter)
{   std::list<ScheduleItem>::iterator pos(findfreepos(items_, si));
    if (pos != 0)
        return 1;
    else
    {   sibefore.begin_ = si.getbegin();
        sibefore.end_ = si.getend();
        siafter.begin_ = si.getbegin();
        siafter.end_ = si.getend();
        for (std::list<ScheduleItem>::iterator i = items_.begin(); i != items_.end() || !(*i > sibefore); i++)
            if (!(*i < sibefore))
            {   sibefore.end_ = *i.getend() + sibefore.getlength();
                sibefore.begin_ = *i.getbegin();
            }
        for (std::list<ScheduleItem>::iterator i = items_.end(); !(*i < siafter); --i)
        {   if (!(*i > siafter))
            {   siafter.begin_ = *i.getbegin() - siafter.getlength();
                siafter.end_ = *i.getbegin()
            }
            if (*i == items_.begin())
                break;
        }
        return 0;
    }
}

the errors I get are all like this:
17 C:\Documents and Settings\ken\Desktop\struII\test\schedule.h expected `,' or `...' before '&' token
17 C:\Documents and Settings\ken\Desktop\struII\test\schedule.h ISO C++ forbids declaration of `ScheduleItem' with no type

etc...

if anybody knows what is causing this his help would be much appreciated.

EDIT:
I will include some more code that might be useful.

here is findfreepos, used in check_item

Code:

// findfreepos.cc

#include <list>
#include "scheduleitem.h"

std::list<ScheduleItem>::iterator findfreepos(std::list<ScheduleItem>& lst, const ScheduleItem& x)
{   for (std::list<ScheduleItem>::iterator i = lst.begin(); ; ++i)
    {   if (i == lst.end() || (*i > x))
            return i;
        else if (!(*i < x))
            return 0;
    }
}

and here is the mainfunction where I also include schedule.h

Code:

// main.cc

#include <iostream>
#include "scheduleitem.h"
#include "schedule.h"

int main()
{   Schedule s;
    while(true)
    {   std::cout << "give begin, end and description:\n";
        ScheduleItem i(std::cin);
        if (i.getbegin() < 10)
            break;
        s.insert_item(i);
        std::cout << s;
    }
    while(true)
    {   std::cout << "give begin, end and description:\n";
        ScheduleItem i(std::cin);
        if (i.getbegin() < 10)
            break;
        s.remove_item(i);
        std::cout << s;
    }
    return 0;
}

I just noticed some other strange thing.
if I change the order of includes in main.cc
(just switching #include "scheduleitem.h" and #include "schedule.h")
it gives totally different error messages.
it just says:

14 C:\Documents and Settings\ken\Desktop\struII\test\scheduleitem.h `Schedule' has not been declared


thanks in advance,

ken