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[–] 187 points 1 year ago (5 children)
typedef struct {
    bool a: 1;
    bool b: 1;
    bool c: 1;
    bool d: 1;
    bool e: 1;
    bool f: 1;
    bool g: 1;
    bool h: 1;
} __attribute__((__packed__)) not_if_you_have_enough_booleans_t;
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  • [–] 16 points 1 year ago (1 child)

    This was gonna be my response to OP so I'll offer an alternative approach instead:

    typedef enum flags_e : unsigned char {
      F_1 = (1 << 0),
      F_2 = (1 << 1),
      F_3 = (1 << 2),
      F_4 = (1 << 3),
      F_5 = (1 << 4),
      F_6 = (1 << 5),
      F_7 = (1 << 6),
      F_8 = (1 << 7),
    } Flags;
    
    int main(void) {
      Flags f = F_1 | F_3 | F_5;
      if (f & F_1 && f & F_3) {
        // do F_1 and F_3 stuff
      }
    }
    
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  • [–] 146 points 1 year ago (16 children)
  • [–] 159 points 1 year ago (15 children)

    And compiler. And hardware architecture. And optimization flags.

    As usual, it's some developer that knows little enough to think the walls they see around enclose the entire world.

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  • [–] 135 points 1 year ago (23 children)

    I set all 8 bits to 1 because I want it to be really true.

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  • [–] 94 points 1 year ago* (18 children)

    01111111 = true

    11111111 = negative true = false

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  • [–] 13 points 1 year ago

    Could also store our bools as floats.

    00111111100000000000000000000000 is true and 10111111100000000000000000000000 is negative true.

    Has the fun twist that true & false is true and true | false is false .

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    [–] 96 points 1 year ago (3 children)

    string boolEnable = "True";

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  • [–] 91 points 1 year ago (10 children)

    Then you need to ask yourself: Performance or memory efficiency? Is it worth the extra cycles and instructions to put 8 bools in one byte and & 0x bitmask the relevant one?

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    [–] 57 points 1 year ago (1 child)

    Wait till you find out about alignment and padding

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    [–] 53 points 1 year ago (6 children)

    Back in the day when it mattered, we did it like

    #define BV00		(1 <<  0)
    #define BV01		(1 <<  1)
    #define BV02		(1 <<  2)
    #define BV03		(1 <<  3)
    ...etc
    
    #define IS_SET(flag, bit)	((flag) & (bit))
    #define SET_BIT(var, bit)	((var) |= (bit))
    #define REMOVE_BIT(var, bit)	((var) &= ~(bit))
    #define TOGGLE_BIT(var, bit)	((var) ^= (bit))
    
    ....then...
    #define MY_FIRST_BOOLEAN BV00
    SET_BIT(myFlags, MY_FIRST_BOOLEAN)
    
    
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    [–] 40 points 1 year ago (8 children)

    In the industrial automation world and most of the IT industry, data is aligned to the nearest word. Depending on architecture, that's usually either 16, 32, or 64 bits. And that's the space a single Boolean takes.

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  • [–] 20 points 1 year ago (7 children)

    That's why I primarily use booleans in return parameters, beyond that I'll try to use bitfields. My game engine's tilemap format uses a 32 bit struct, with 16 bit selecting the tile, 12 bit selecting the palette, and 4 bit used for various bitflags (horizontal and vertical mirroring, X-Y axis invert, and priority bit).

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  • [–] 30 points 1 year ago (6 children)

    Bit fields are a necessity in low level networking too.

    They're incredibly useful, I wish more people made use of them.

    I remember I interned at a startup programming microcontrollers once and created a few bitfields to deal with something. Then the lead engineer went ahead and changed them to masked ints. Because. The most aggravating thing is that an int size isn't consistent across platforms, so if they were ever to change platforms to a different word length, they'd be fucked as their code was full of platform specific shenanigans like that.

    /rant

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  • [–] 39 points 1 year ago* (7 children)

    The 8-bit Intel 8051 family provides a dedicated bit-addressable memory space (addresses 20h-2Fh in internal RAM), giving 128 directly addressable bits. Used them for years. I'd imagine many microcontrollers have bit-width variables.

    bit myFlag = 0;

    Or even return from a function:

    bit isValidInput(unsigned char input) { // Returns true (1) if input is valid, false (0) otherwise return (input >= '0' && input <= '9'); }

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    [–] 34 points 1 year ago (1 child)
  • [–] 33 points 1 year ago (2 children)

    std::vector<bool> fits eight booleans into one byte.

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    [–] 27 points 1 year ago (11 children)

    It's far more often stored in a word, so 32-64 bytes, depending on the target architecture. At least in most languages.

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    [–] 23 points 1 year ago (3 children)

    if wasting a byte or seven matters to you, then then you need to be working in a lower level language.

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  • [–] 22 points 1 year ago (1 child)

    Joke’s on you, I always use 64 bit wide unsigned integers to store a 1 and compare to check for value.

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    [–] 21 points 1 year ago* (1 child)

    I have a solution with a bit fields. Now your bool is 1 byte :

    struct Flags {
        bool flag0 : 1;
        bool flag1 : 1;
        bool flag2 : 1;
        bool flag3 : 1;
        bool flag4 : 1;
        bool flag5 : 1;
        bool flag6 : 1;
        bool flag7 : 1;
    };
    

    Or for example:

    struct Flags {
        bool flag0 : 1;
        bool flag1 : 1:
        int x_cord : 3;
        int y_cord : 3;
    };
    
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    [–] 21 points 1 year ago (3 children)
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    [–] 17 points 1 year ago (1 child)
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    [–] 15 points 1 year ago (1 child)

    just like electronic components, they sell the gates by the chip with multiple gates in them because it's cheaper

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    [–] 15 points 1 year ago (3 children)

    Wait until you hear about alignment

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    [–] 14 points 1 year ago (10 children)

    Are you telling me that no compiler optimizes this? Why?

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  • [–] 35 points 1 year ago

    It would be slower to read the value if you had to also do bitwise operations to get the value.

    But you can also define your own bitfield types to store booleans packed together if you really need to. I would much rather that than have the compiler do it automatically for me.

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    [–] 12 points 1 year ago (1 child)

    This reminds me that I actually once made a class to store bools packed in uint8 array to save bytes.

    Had forgotten that. I think i have to update the list of top 10 dumbest things i ever did.

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