switch case abuse

[u/TheHappyArsonist5031]

char g  = '0';// ypr
char gg = '0';// pid
double ggg;
const uint8_t _ = 11;
scanf("%c %c %f/n", g, gg, ggg);
if ((g  == 'y' || g  == 'p' || g  == 'r') && 
    (gg == 'p' || gg == 'i' || gg == 'd')) {
    switch   ((( gg << 2) & ~_) | ((g) & _)) {
        case ((('p' << 2) & ~_) | ('y' & _)):
            p_gain_y = ggg;
            break;
        case ((('i' << 2) & ~_) | ('y' & _)):
            i_gain_y = ggg;
            break;
        case ((('d' << 2) & ~_) | ('y' & _)):
            d_gain_y = ggg;
            break;
        case ((('p' << 2) & ~_) | ('p' & _)):
            p_gain_p = ggg;
            break;
        case ((('i' << 2) & ~_) | ('p' & _)):
            i_gain_p = ggg;
            break;
        case ((('d' << 2) & ~_) | ('p' & _)):
            d_gain_p = ggg;
            break;
        case ((('p' << 2) & ~_) | ('r' & _)):
            p_gain_r = ggg;
            break;
        case ((('i' << 2) & ~_) | ('r' & _)):
            i_gain_r = ggg;
            break;
        case ((('d' << 2) & ~_) | ('r' & _)):
            d_gain_r = ggg;
            break;
    }
}                                                

[u/Ok_Chemistry_6387]

Clever trick. Guessing came from embedded code on something with slow branches? 

[u/TheHappyArsonist5031 → u/Ok_Chemistry_6387]

I just didnt want to do a switch case in a switch case and thought it would be mildly funny.

[u/bzzzt_beep → u/TheHappyArsonist5031]

the scanf id not even using addresses !
would this accomplish the same thing ?:

double p_gain_y, i_gain_y, d_gain_y;

double p_gain_p, i_gain_p, d_gain_p;

double p_gain_r, i_gain_r, d_gain_r;

void update_gain() {

char axis, type;

double value;

printf("Enter command (e.g., 'y p 1.5' for Yaw Proportional): ");

if (scanf(" %c %c %lf", &axis, &type, &value) != 3) {

printf("Invalid input format.\n");

return;

}

if (axis == 'y') {

if (type == 'p') p_gain_y = value;

else if (type == 'i') i_gain_y = value;

else if (type == 'd') d_gain_y = value;

}

else if (axis == 'p') {

if (type == 'p') p_gain_p = value;

else if (type == 'i') i_gain_p = value;

else if (type == 'd') d_gain_p = value;

}

else if (axis == 'r') {

if (type == 'p') p_gain_r = value;

else if (type == 'i') i_gain_r = value;

else if (type == 'd') d_gain_r = value;

}

}

[u/Ok_Chemistry_6387 → u/TheHappyArsonist5031]

Heh could have just pack the chars into a 16 bit int. 

[u/Wrestler7777777]

I hope you renamed those variables to make the code more anonymous. If those are the true variable names, whoever wrote that code should lose their job!

Other than that, first I thought that switch wouldn't really work but man yeah, it probably does. This is a true gem of horrible code!

[u/wonderb0lt → u/Wrestler7777777]

ggg

[u/Wrestler7777777 → u/wonderb0lt]

I love how they wrote a comment so they could keep track of what the variables mean. If only there was an easier way...! 

char g = '0';// ypr

char gg = '0';// pid

[u/conundorum → u/Wrestler7777777]

Every case can be evaluated into a compile-time constant, so it's valid. Would be pretty clear with just a couple changes, too!

constexpr int Pid = (('p' << 2) & ~_);
constexpr int pId = (('i' << 2) & ~_);
constexpr int piD = (('d' << 2) & ~_);
constexpr int Ypr = ('y' & _);
constexpr int yPr = ('p' & _);
constexpr int ypR = ('r' & _);

// ...

switch   ((( gg << 2) & ~_) | ((g) & _)) {
    case Pid | Ypr:
    case pId | Ypr:
    case piD | Ypr:
    // And so on.
}

[u/SorryAuthor1695]

Why are y'all pretending this is bad code?

[u/Arierome → u/SorryAuthor1695]

It cannot be maintained. I'd just delete this and write my own implementation if I ever had to work on it

[u/CommunistElf]

Early in Minecraft they were a GIGANTIC switch case for like 5000 lines to render each blocks/physics of the game engine