How to obtain iterator to beginning of inserted elements in list

[JurgenvonOerthel@hotmail.com]

I want to replace one element in a list<stringby a list<stringand
I need to obtain an iterator to the first element in the inserted
list.
In code:

void replace_element _by_list(list<s tring&my_list,
list<string>::i terator
&iter_to_remove ,
const list<string>
&list_to_insert ) {
list<string>::i terator next_iter = my_list.erase(i ter_to_remove);
my_list.insert( next_iter, list_to_insert. begin(),
list_to_insert. end());
// Does 'iter_to_remove ' point to the first element of the inserted
list, or is it invalid?
}

When I try this code I find that 'iter_to_remove ' indeed points to the
first element of the inserted list. However, I'm wondering whether
that is guaranteed.

[Victor Bazarov]

Re: How to obtain iterator to beginning of inserted elements in list

JurgenvonOerthe l@hotmail.com wrote:

I want to replace one element in a list<stringby a list<stringand
I need to obtain an iterator to the first element in the inserted
list.
In code:
>
void replace_element _by_list(list<s tring&my_list,
list<string>::i terator
&iter_to_remove ,
const list<string>
&list_to_insert ) {
list<string>::i terator next_iter = my_list.erase(i ter_to_remove);

Add
list<string>::i terator prev_iter = next_iter;
if (prev_iter == my_list.begin() )
prev_iter = my_list.end();
else
--prev_iter;

my_list.insert( next_iter, list_to_insert. begin(),
list_to_insert. end());

What does 'insert' return?

// Does 'iter_to_remove ' point to the first element of the inserted
list, or is it invalid?

'iter_to_remove ' is invalid. However, you can return 'prev_iter' here.
The catch, of course, is that if you're removing the very first element
in the list, you'll get 'end()'.

}
>
When I try this code I find that 'iter_to_remove ' indeed points to the
first element of the inserted list. However, I'm wondering whether
that is guaranteed.

Nope.

V
--
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I do not respond to top-posted replies, please don't ask

[Abhishek Padmanabh]

Re: How to obtain iterator to beginning of inserted elements in list

On Dec 7, 8:17 pm, JurgenvonOert.. .@hotmail.com wrote:

I want to replace one element in a list<stringby a list<stringand
I need to obtain an iterator to the first element in the inserted
list.
In code:
>
void replace_element _by_list(list<s tring&my_list,
list<string>::i terator
&iter_to_remove ,
const list<string>
&list_to_insert ) {
list<string>::i terator next_iter = my_list.erase(i ter_to_remove);
my_list.insert( next_iter, list_to_insert. begin(),
list_to_insert. end());
// Does 'iter_to_remove ' point to the first element of the inserted
list, or is it invalid?
>
}
>
When I try this code I find that 'iter_to_remove ' indeed points to the
first element of the inserted list. However, I'm wondering whether
that is guaranteed.

This is not guaranteed. It is invalid. You could, however, get the
iterator to the first element of the inserted range as below:

void replace_element _by_list(list<s tring&my_list,
list<string>::i terator
&iter_to_remove ,
const list<string>
&list_to_insert ) {
list<string>::i terator next_iter = my_list.erase(i ter_to_remove);
list<string>::i terator prev_to_next_it er = --next_iter;
my_list.insert( next_iter, list_to_insert. begin(),
list_to_insert. end());
// Does 'iter_to_remove ' point to the first element of the inserted
list, or is it invalid?
iter_to_remove = ++prev_to_next_ iter;
//iter_to_remove is guaranteed to point to the first element of the
//inserted list/range
}

[JurgenvonOerthel@hotmail.com]

Re: How to obtain iterator to beginning of inserted elements in list

On Dec 7, 4:30 pm, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Add
list<string>::i terator prev_iter = next_iter;
if (prev_iter == my_list.begin() )
prev_iter = my_list.end();
else
--prev_iter;

I was afraid I would have to do something ugly like this.

What does 'insert' return?

That's my point: it returns void. I think it should return an iterator
to the first inserted element. That's what 'insert' of a single
element does.