incrementing an STL list interator

[Abubakar]

Hi,

lets say I have a iterator of the type:
list<string>::const_iterator itr;
lets say its at some position in a given list. Now I can goto the next item
by simply doing a itr++. But I want to increment more than just 1. Lets says
I want to increment the itr 3 times, ie being able to do something like
itr+=3. But as the += is not defined for that iterator class, I cant do
that. What should I do?

Regards,

-ab.

[Doug Harrison [MVP]]

On Wed, 13 Dec 2006 22:42:32 +0500, "Abubakar" <em**********@yahoo.com>
wrote:

>Hi,

lets say I have a iterator of the type:
list<string>::const_iterator itr;
lets say its at some position in a given list. Now I can goto the next item
by simply doing a itr++. But I want to increment more than just 1. Lets says
I want to increment the itr 3 times, ie being able to do something like
itr+=3. But as the += is not defined for that iterator class, I cant do
that. What should I do?

Look into std::advance. It can handle any iterator type and will repeatedly
increment non-random access iterators as necessary. The operator isn't
provided for non-random access iterators to emphasize that increment values

1 aren't as simple and efficient as pointer arithmetic.

--
Doug Harrison
Visual C++ MVP

[Abubakar]

Wow, pretty cool. Thanks :)

-ab.

"Doug Harrison [MVP]" <ds*@mvps.orgwrote in message
news:bs********************************@4ax.com...

On Wed, 13 Dec 2006 22:42:32 +0500, "Abubakar" <em**********@yahoo.com>
wrote:

>>Hi,

lets say I have a iterator of the type:
list<string>::const_iterator itr;
lets say its at some position in a given list. Now I can goto the next
item
by simply doing a itr++. But I want to increment more than just 1. Lets
says
I want to increment the itr 3 times, ie being able to do something like
itr+=3. But as the += is not defined for that iterator class, I cant do
that. What should I do?

Look into std::advance. It can handle any iterator type and will
repeatedly
increment non-random access iterators as necessary. The operator isn't
provided for non-random access iterators to emphasize that increment
values

>1 aren't as simple and efficient as pointer arithmetic.

--
Doug Harrison
Visual C++ MVP