Sequence Class

[pat270881]

hello,

I have to implement a sequence class, however the header file is
predefined

class sequence
{
public:
// TYPEDEFS and MEMBER CONSTANTS
typedef double value_type;
typedef std::size_t size_type;
static const size_type DEFAULT_CAPACITY = 30;
// CONSTRUCTORS and DESTRUCTOR
sequence(size_type initial_capacity = DEFAULT_CAPACITY);
sequence(const sequence& source);
~sequence( );
// MODIFICATION MEMBER FUNCTIONS
void resize(size_type new_capacity);
void start( );
void advance( ); //set the current_index to the next number in
the array
void insert(const value_type& entry); //insert before the
number with the current index
void attach(const value_type& entry); //insert after the number
with the current index
void remove_current( );
void operator =(const sequence& source);
// CONSTANT MEMBER FUNCTIONS
size_type size( ) const;
bool is_item( ) const;
value_type current( ) const;
private:
value_type* data; //das array mit den zahlen drinnen
size_type used; //wieviele zahlen in dem array stehen
size_type current_index;
size_type capacity;
};
 

Unfortunately, I guess something is wrong with the copy constructor, or
the insert, attach or resize function:

sequence::sequence(const sequence& source)
{
data = new value_type[source.capacity];
capacity = source.capacity;
used = source.used;
current_index = source.current_index;
copy(source.data, source.data + used, data);
}
 

Here the insert, attach and resize function:

 
void sequence::insert(const value_type& entry)
{
if(used == capacity)
resize(used);
 
if(!(is_item()))
current_index = 0;
 
for(int i = used; i current_index; i--)
{
data[i] = data[i-1];
}
data[current_index] = entry;
++used;
}
 
void sequence::attach(const value_type& entry)
{
if(used == capacity)
resize(used);
 
if(current_index >= used)
{
start();
advance();
advance();
}
if(used!=0)
{
for(int i = used; i current_index+1; i--)
{
data[i] = data[i-1];
}
data[current_index+1] = entry;
current_index++;
}
else
{
data[current_index] = entry;
}
++used;
}
 
void sequence::resize (size_type new_capacity)
{
value_type* larger_array;
 
if(new_capacity < used)
new_capacity = used;
 
larger_array = new value_type[new_capacity];
copy(data, data + used + current_index, larger_array);
delete[] data;
data = larger_array;
capacity = new_capacity;
}
 

Has anybody an idea what went wrong here? I am working on the problem
fixing for such a long time but I haven't found the error yet...:((

pat

[red floyd]

pat270881 wrote:

>
I have already debug the program and the error occurs here:

// Test copying of a sequence with cursor near the middle.
cout << "Copy constructor test: for a sequence with cursor near
middle." << endl;
original.insert (2);

but I simply don't know why...? :((

No, that's the symptom. Mlimber is telling you that if you see
bad_alloc, that means that new is failing. That's your potential
cause. Don't fixate on what you think is wrong. If you were certain,
you wouldn't have come here. If you ask someone's advice, then listen
to it.

If you're seeing bad_alloc somewhere, that means that new is failing
(not that you're overwriting heap, though that may happen as well). Put
a break point on your new statements, and check that you're passing sane
values as the sizes.

[Alan Johnson]

pat270881 wrote:

I have already debug the program and the error occurs here:

// Test copying of a sequence with cursor near the middle.
cout << "Copy constructor test: for a sequence with cursor near
middle." << endl;
original.insert (2);

but I simply don't know why...? :((

You are making it too hard to help you. Right now if I wanted to debug
your program, I'd have to collect together several pieces of it from
multiple posts, and then I'd still have to write some code of my own to
have anything that would compile and run.

Your best bet is to post a complete program that demonstrates your
problem. This means that I could copy and paste directly from your
post into my editor, compile, and see your problem (Hint: a complete
program has a main function, and you haven't posted one anywhere).

--
Alan Johnson

[Thomas J. Gritzan]

pat270881 schrieb:

void sequence::inser t(const value_type& entry)
{
if(used == capacity)
resize(used);

if(!(is_item()) )
current_index = 0;

for(int i = used; i current_index; i--)
{
data[i] = data[i-1];
}
data[current_index] = entry;
++used;
}

[...]

Has anybody an idea what went wrong here? I am working on the problem
fixing for such a long time but I haven't found the error yet...:((

resize(used);
should be
resize(used+1);

Otherwise you are accessing data[used] in the for-loop, which is one past
the last element.

Why don't you use std::vector?

--
Thomas
http://www.netmeister.org/news/learn2quote.html

[mlimber]

Thomas J. Gritzan wrote:

Why don't you use std::vector?

Because this is homework.

Cheers! --M

[pat270881]

Sorry, that I cost you so much nerves, that was the error - when a
handed over the used to the resize function I haven't increased the
used, now I use 2*used in insert and attach and now it works :))

Thank you very much for your help!!!