what does it use two "!!"

[anish singh]

!! is generally used to make the return bool value.
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On Mon, Apr 1, 2013 at 12:43 PM, Ben Wu <crayben at yahoo.cn> wrote:

>
>
> Dear All：
> 1> I found some placeuse two "!!", what's means
>     if(button->gpio != INVALID_GPIO)
>         state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^
> button->active_low);
>     else
>         state = !!button->adc_state;
>
> 2> is there some MSN group to study linux kernel or discuss it ?
>
> Thanks and Best Regards
> Ben Wu
> MSN:crayben at yahoo.cn
>
>
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