Cによるアナログ時計

clock.c

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define SIZE 40

void set(char *buf, int x, int y, char c) {
    x += SIZE;
    y += SIZE / 2;
    buf[x + y * (SIZE + 1) * 2] = c;
}

void draw(const char *buf) {
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j <= SIZE * 2; j++) {
            putchar(buf[i * (SIZE + 1) * 2 + j]);
        }
        putchar('\n');
    }
}

int aboutCompare(double a, double b, int w) {
    return -w <= a - b && a - b <= w;
}

int orthant(double x, double y) {
    if (x >= 0) {
        if (y > 0)
            return 1;
        else
            return 2;
    } else {
        if (y >= 0)
            return 4;
        else
            return 3;
    }
}

void build(char *canvas, int hour, int minute, int second) {
    int xs = (SIZE * 2) * cos(second * M_PI / 30.0 - M_PI_2) * 0.45;
    int ys = SIZE * sin(second * M_PI / 30.0 - M_PI_2) * 0.45;

    int xm = (SIZE * 2) * cos((60 * minute + second) * M_PI / 1800.0 - M_PI_2) * 0.4;
    int ym = SIZE * sin((60 * minute + second) * M_PI / 1800.0 - M_PI_2) * 0.4;

    int xh = (SIZE * 2) * cos((3600 * hour + 60 * minute + second) * M_PI / 21600.0 - M_PI_2) * 0.25;
    int yh = SIZE * sin((3600 * hour + 60 * minute + second) * M_PI / 21600.0 - M_PI_2) * 0.25; 

    for (int y = SIZE / 2; y > -SIZE / 2; y--) {
        for (int x = -SIZE; x <= SIZE; x++) {
            // outline
            if ((int)(pow((double)x / SIZE, 2) + pow((double)y * 2 / SIZE, 2)) == 1) {
                set(canvas, x, y, 'o');
                continue;
            }

            // hour
            if (aboutCompare(xh * y, yh * x, 17) && orthant(x, y) == orthant(xh, yh) && abs(x) <= abs(xh) && abs(y) <= abs(yh)) {
                set(canvas, x, y, 'h');
                continue;
            }

            // minute
            if (aboutCompare(xm * y, ym * x, 12) && orthant(x, y) == orthant(xm, ym) && abs(x) <= abs(xm) && abs(y) <= abs(ym)) {
                set(canvas, x, y, 'm');
                continue;
            }

            // second
            if (aboutCompare(xs * y, ys * x, 10) && orthant(x, y) == orthant(xs, ys) && abs(x) <= abs(xs) && abs(y) <= abs(ys)) {
                set(canvas, x, y, 's');
                continue;
            }

            // axis
            if (x == 0) set(canvas, x, y, '|');
            if (y == 0) set(canvas, x, y, '-');
        }
    }
    set(canvas, 0, 0, '@');
}

int main(void) {
    char *canvas = (char *)malloc(SIZE * (SIZE + 1) * 2);
    memset(canvas, ' ', SIZE * (SIZE + 1) * 2);
    build(canvas, 7, 22, 53);
    draw(canvas);
    free(canvas);
    return 0;
}