I agree it is possible in C++. However you have to accept that your code
will run slow on almost all processors: most processors do not have
hardware support for 3byte integers, so you have to implement ALL
operations in software. You could write something like:
class int3{
char d[3];
public:
int3(int x){
assert(x<(1l<<24));
d[0]=x%256;
d[1]=(x/265)%256;
d[2]=(x/256/256)%256;
}
friend int3 operator +(int3, int3);
};
int3 operator +(int3 x, int3 y){
int3 z;
for(int i =0;i <3;i++)
z.d[i]=x.d[i]+y.d[i];
return z;
}
However, I'm skipping some important parts:
- how to treat overflow, if one of the three summations gives a result >
128 (C++ does not guarantee what will happen then, you have to check the
values before adding them and the do the overflow- handling yourself.)
- some test code ;)
- for std::sort you can either define " bool operator<", or you define a
functor class doing that comparison, and pass that functor to std::sort
Axel
Am 06.03.2012 06:56 schrieb "Neal Zane" <[email protected]>:
> I am thinking putting those guys in 256 buckets each holding 16 bit shorts
> and some arrangements would make each bucket sortable using sort().
> On Mar 5, 2012 3:14 PM, "Βαγγέλης Μαμαλάκης" <[email protected]> wrote:
>
>> Well I a writing a program for a competition and I am initializing some
>> arrays whose values will be less than 1million so I am trying to save
>> memory. I am also curious.
>> Would it be possible to give me some example code or psedocode.
>> Thanks for your interest.
>> On Mar 6, 2012 12:44 AM, "Damian Walczak" <[email protected]>
>> wrote:
>>
>>> Hi
>>>
>>> On Mon, Mar 5, 2012 at 8:27 PM, Sidhartha Mani <[email protected]>wrote:
>>>
>>>> You could
>>>> use 3 char vars to hold your values, but i believe, the size of char
>>>> differs on different architectures.
>>>>
>>>
>>> AFAIR size of char is always 1 byte in C/C++ and it doesn't matter what
>>> architecture you are using.
>>>
>>> the implementation of this though. I think std::sort() only works and
>>>> is meant for abstract data structures like vectors and such, not on
>>>> elementary ones like int.
>>>>
>>>
>>> You can use std::sort for sorting arrays, example is even on wikipedia
>>> [1]
>>> If you write your own class, it's enough to write proper comparison
>>> function and use second version of std::sort [2]
>>>
>>>
>>> If I may ask - why do you need 3-byte 'int' ?
>>>
>>> Best,
>>> D.
>>>
>>> [1] http://en.wikipedia.org/wiki/Sort_(C%2B%2B)
>>> [2] http://www.cplusplus.com/reference/algorithm/sort/
>>>
>>>
>>>
>>>> Sidhartha
>>>>
>>>>
>>>>
>>>> On 06-Mar-2012, at 12:42 AM, bugos <[email protected]> wrote:
>>>>
>>>> > Hello,
>>>> > is there a way to define my own data type, which will be idetical to
>>>> > an int, but just 3 bytes size? i must be able to use it as an int and
>>>> > even use std::sort() with it.
>>>> >
>>>> > --
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