Re: [Boost-users] circular_buffer: How to make push_back() increase capacity?

Subject: Re: [Boost-users] circular_buffer: How to make push_back() increase capacity?
From: strasser_at_[hidden]
Date: 2009-08-30 09:36:14

Zitat von Cory Nelson <phrosty_at_[hidden]>:

> On Fri, Aug 28, 2009 at 3:17 PM, Robert Dailey<rcdailey_at_[hidden]> wrote:
>> Hello,
>> I have a list of colors that I need to be able to cycle through, either by
>> rotating the container or by using an iterator that will rotate (i.e. return
>> to the beginning when I increment at the end, and vice-versa). The goal is
>> to be able to iterate through the container in a circular way and process
>> all of the colors repeatedly.
>> I chose a boost::circular_buffer for this job, I assumed it was the perfect
>> tool for the job. It works great, except I would like to be able to call
>> push_back() to add all of my colors to the buffer without having to call
>> set_capacity() on it first. It's a minor thing, but omitting the call to
>> set_capacity() would make it slightly more scalable/manageable since I won't
>> have to keep incrementing the size of the capacity each time I want to add
>> colors to the buffer.
>> How can I achieve this?

a circular buffer is designed to have a specific capacity.
you can cycle through any container.

>
>
> I'm not familiar with circular_buffer, but something quick n' dirty:
>
> std::vector<color> colors;
>
> colors.push_back(color());
> ...
>
> for(std::vector<color>::size_type i = 0; i < colors.size(); i = (i +
> 1) % colors.size())
> {
>   color &c = colors[i];
> }

I've got an easier way to write that:

while(true);

if you want to end the iteration at some point:

container::iterator it=start;
while(...){
   ...
   if(it == container.end()) it=container.begin();
}

if you often need to do something like that consider writing an own  
iterator. that can be achieved in just a view lines of code in this  
case with boost::iterator_adaptor.