A function for a generic STL container

[Nafai]

Hi I want to write a function which erases al the repeated elements in a
range. How should be the prototype?

template <class Iterator>
void eraseRepeated(I terator begin, Iterator end);

doesn't work because I need the container to write: container.erase (p),
where p is an iterator.

[Alf P. Steinbach]

* Nafai:

Hi I want to write a function which erases al the repeated elements in a
range. How should be the prototype?

template <class Iterator>
void eraseRepeated(I terator begin, Iterator end);

doesn't work because I need the container to write: container.erase (p),
where p is an iterator.

Check out std::unique.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Nafai]

Alf P. Steinbach escribió:

* Nafai:

Hi I want to write a function which erases al the repeated elements in a
range. How should be the prototype?

template <class Iterator>
void eraseRepeated(I terator begin, Iterator end);

doesn't work because I need the container to write: container.erase (p),
where p is an iterator.

Check out std::unique.

Unique only erases consecutive elements. I want to erase all of them.
And I don't want to sort them.

But above all I would like to know how to program a function like that,
which can get any container and do something with its iterators.

[davidrubin]

Nafai wrote:

Alf P. Steinbach escribió:

* Nafai:

Hi I want to write a function which erases al the repeated elements in a range. How should be the prototype?

template <class Iterator>
void eraseRepeated(I terator begin, Iterator end);

doesn't work because I need the container to write: container.erase (p),where p is an iterator.

Check out std::unique.

Unique only erases consecutive elements. I want to erase all of them.

And I don't want to sort them.

But above all I would like to know how to program a function like that, which can get any container and do something with its iterators.

No such function exists because different containers have different
"erase" semantics. For example, an algorithm that erases sequential
iterators may work for one container, but may yield undefined behavior
for another. The best you can do is to copy the range, remove the
range, and then add back unique (or non-repeated) elements from the
copied data, but this is very inefficient. /david

[Alf P. Steinbach]

* Nafai:

Alf P. Steinbach escribió:

* Nafai:

Hi I want to write a function which erases al the repeated elements in a
range. How should be the prototype?

template <class Iterator>
void eraseRepeated(I terator begin, Iterator end);

doesn't work because I need the container to write: container.erase (p),
where p is an iterator.

Check out std::unique.

Unique only erases consecutive elements. I want to erase all of them.
And I don't want to sort them.

I don't think you understand the requirements.

Some way of identifying an element as duplicate is needed.

If not consecutive, and no sorting, you'll need to register elements in
a hash table or something like that.

But above all I would like to know how to program a function like that,
which can get any container and do something with its iterators.

See std::unique.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Nafai]

Alf P. Steinbach wrote:

Some way of identifying an element as duplicate is needed.

A and B are duplicate if and only if A==B.

[Nafai]

Alf P. Steinbach wrote:

* Nafai:

Alf P. Steinbach escribió:

> * Nafai:
>
>>Hi I want to write a function which erases al the repeated elements in
>>a
>> range. How should be the prototype?
>>
>>template <class Iterator>
>>void eraseRepeated(I terator begin, Iterator end);
>>
>>doesn't work because I need the container to write: container.erase (p),
>>where p is an iterator.
>
>
> Check out std::unique.
>

Unique only erases consecutive elements. I want to erase all of them.
And I don't want to sort them.

I don't think you understand the requirements.

Some way of identifying an element as duplicate is needed.

If not consecutive, and no sorting, you'll need to register elements in
a hash table or something like that.

But above all I would like to know how to program a function like that,
which can get any container and do something with its iterators.

See std::unique.

Let's see. It's quite simple. I have a collection C (ie. list or vector):
C=(1 4 4 2 1 1 4) and I get: C'=(1 4 2)

The algorithm is just this:

insert all elements of C into a set.

iterate through C and check if each element is in the set.
If it is, erase it from the set.
If it isn't erase it from C.

Or even more simpler (and suitable for any collection):

....
If it is, erase it from the set and insert it into C'.
If it isn't do nothing.
I just need to know how to declare the prototype!! ("template". ..)

[Kristo]

Nafai wrote:

Alf P. Steinbach wrote:

* Nafai:

Alf P. Steinbach escribió:
> * Nafai:
>
>>Hi I want to write a function which erases al the repeated elements in >>a
>> range. How should be the prototype?
>>
>>template <class Iterator>
>>void eraseRepeated(I terator begin, Iterator end);
>>
>>doesn't work because I need the container to write: container.erase (p), >>where p is an iterator.
>
>
> Check out std::unique.
>

Unique only erases consecutive elements. I want to erase all of them. And I don't want to sort them.

I don't think you understand the requirements.

Some way of identifying an element as duplicate is needed.

If not consecutive, and no sorting, you'll need to register elements in a hash table or something like that.

But above all I would like to know how to program a function like that, which can get any container and do something with its iterators.

See std::unique.

Let's see. It's quite simple. I have a collection C (ie. list or
vector):
C=(1 4 4 2 1 1 4) and I get: C'=(1 4 2)

The algorithm is just this:

insert all elements of C into a set.

iterate through C and check if each element is in the set.
If it is, erase it from the set.
If it isn't erase it from C.

Or even more simpler (and suitable for any collection):

...
If it is, erase it from the set and insert it into C'.
If it isn't do nothing.
I just need to know how to declare the prototype!! ("template". ..)

Does this suit you?

template <class T>
void eraseRepeated(T &container);

Kristo

[Nafai]

Kristo escribió:

Nafai wrote:

Alf P. Steinbach wrote:

* Nafai:

Alf P. Steinbach escribió:

>* Nafai:
>
>
>>Hi I want to write a function which erases al the repeated
elements in
a
>> range. How should be the prototype?
>>
>>templat e <class Iterator>
>>void eraseRepeated(I terator begin, Iterator end);
>>
>>doesn't work because I need the container to write:
container.erase (p),
where p is an iterator.
>
>
>Check out std::unique.
>

Unique only erases consecutive elements. I want to erase all of
them.
And I don't want to sort them.

I don't think you understand the requirements.

Some way of identifying an element as duplicate is needed.

If not consecutive, and no sorting, you'll need to register
elements in
a hash table or something like that.

But above all I would like to know how to program a function like
that,
which can get any container and do something with its iterators.

See std::unique.

Let's see. It's quite simple. I have a collection C (ie. list or
vector):
C=(1 4 4 2 1 1 4) and I get: C'=(1 4 2)

The algorithm is just this:

insert all elements of C into a set.

iterate through C and check if each element is in the set.
If it is, erase it from the set.
If it isn't erase it from C.

Or even more simpler (and suitable for any collection):

...
If it is, erase it from the set and insert it into C'.
If it isn't do nothing.
I just need to know how to declare the prototype!! ("template". ..)

Does this suit you?

template <class T>
void eraseRepeated(T &container);

Kristo

No, it doesn't. This doesn't work:

template <class T>
void f(T& Container)
{
T::iterator it; // <- parse error before token ';'
it = Container.begin ();
....
}

[Kristo]

Nafai wrote:

Kristo escribió:

Nafai wrote:

Let's see. It's quite simple. I have a collection C (ie. list or
vector):
C=(1 4 4 2 1 1 4) and I get: C'=(1 4 2)

The algorithm is just this:

insert all elements of C into a set.

iterate through C and check if each element is in the set.
If it is, erase it from the set.
If it isn't erase it from C.

Or even more simpler (and suitable for any collection):

...
If it is, erase it from the set and insert it into C'.
If it isn't do nothing.
I just need to know how to declare the prototype!! ("template". ..)

Does this suit you?

template <class T>
void eraseRepeated(T &container);

Kristo

No, it doesn't. This doesn't work:

template <class T>
void f(T& Container)
{
T::iterator it; // <- parse error before token ';'
it = Container.begin ();
...
}

That's because you forgot the typename keyword. The compiler has no
other way of knowing that T::iterator is a type.

typename T::iterator it;

Kristo