unique data types

This is a discussion on unique data types within the C++ Programming forums, part of the General Programming Boards category; Originally Posted by simpleid char is not unsigned by default on my machine. i need to store values no larger ...

  1. #16
    and the hat of sweating
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    Quote Originally Posted by simpleid View Post
    char is not unsigned by default on my machine.
    i need to store values no larger than 255 for each of the three primary color components.

    storing the three color components in to an int was unnecessary since it offered too much space.
    just fyi in case anyone mentions it. and as i've said, too large of data types crashed my app.
    If you need values up to 255, you can't use anything smaller than an unsigned char.

    Also, you might want to do something like this:
    Code:
    typedef unsigned char   color;
    That way, in the future if you decide you need more than 255 shades/color, it will be much easier to change. Plus it would make the meaning of your code clearer.

  2. #17
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    Don't create things that are larger than a few kB on the stack. You only have about 1 MB of stack space on most systems. Allocate such things from the heap.
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    Quote Originally Posted by simpleid View Post
    theoretically, could i make a 4bit type? ... 2bit?
    You could do something along the lines of the vector<bool> specialisation to achieve such a thing. At last that's where I'd start if I were going to make that.
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    theoretically, could i make a 4bit type? ... 2bit?
    i would make a class that emulates a "collection" of such type, and use bitwise operations to implement operations on them. Note that it will be very inefficient though. For this particular case, just allocate the memory on the heap (new or malloc).

  5. #20
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    vector<bool> is evil, and very likely to be deprecated in the next standard.

    Use std::bitset if you have a collection of known size, or boost::dynamic_bitset if it's of unknown size. But in this case, I agree with cyberfish.
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    I worked on a C++ project that simulated a complete chip, and it had, as part of the design, n-bit wide types from 1 to 512 bits. Although, as a space-saving excercise, it wouldn't be particularly useful, since each integer was a class, which takes up more than one byte [because to make it efficient, the class essentially had two fields, one to hold the value and one that was the mask whcih whcih to extract the actual value after any math operation].

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