| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"" |
| Date: |
07 Dec 2007 09:17:43 AM |
| Object: |
How to obtain iterator to beginning of inserted elements in list |
I want to replace one element in a list<string> by a list<string> and
I need to obtain an iterator to the first element in the inserted
list.
In code:
void replace_element_by_list(list<string> &my_list,
list<string>::iterator
&iter_to_remove,
const list<string>
&list_to_insert) {
list<string>::iterator next_iter = my_list.erase(iter_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.
.
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| User: "Victor Bazarov" |
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| Title: Re: How to obtain iterator to beginning of inserted elements in list |
07 Dec 2007 09:30:07 AM |
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wrote:
I want to replace one element in a list<string> by a list<string> and
I need to obtain an iterator to the first element in the inserted
list.
In code:
void replace_element_by_list(list<string> &my_list,
list<string>::iterator
&iter_to_remove,
const list<string>
&list_to_insert) {
list<string>::iterator next_iter = my_list.erase(iter_to_remove);
Add
list<string>::iterator 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
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
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| User: "" |
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| Title: Re: How to obtain iterator to beginning of inserted elements in list |
07 Dec 2007 09:40:24 AM |
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On Dec 7, 4:30 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:
Add
list<string>::iterator 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.
.
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| User: "Abhishek Padmanabh" |
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| Title: Re: How to obtain iterator to beginning of inserted elements in list |
07 Dec 2007 09:38:26 AM |
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On Dec 7, 8:17 pm, wrote:
I want to replace one element in a list<string> by a list<string> and
I need to obtain an iterator to the first element in the inserted
list.
In code:
void replace_element_by_list(list<string> &my_list,
list<string>::iterator
&iter_to_remove,
const list<string>
&list_to_insert) {
list<string>::iterator next_iter = my_list.erase(iter_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<string> &my_list,
list<string>::iterator
&iter_to_remove,
const list<string>
&list_to_insert) {
list<string>::iterator next_iter = my_list.erase(iter_to_remove);
list<string>::iterator prev_to_next_iter = --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
}
.
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