Ecco una versione C della mia risposta Python che utilizza l'istruzione switch invece del ciclo while e riduce l'indicizzazione incrementando un puntatore anziché l'indice dell'array
La dimensione della tabella di ricerca può essere sostanzialmente ridotta usando T [x1 e 0xf] e U [x2 e 0xf] per un paio di istruzioni extra
#include <stdio.h>
#include <math.h>
unsigned short T[] = {0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001,
0xffff, 0x7fff, 0x3fff, 0x1fff, 0x0fff, 0x07ff, 0x03ff, 0x01ff,
0x00ff, 0x007f, 0x003f, 0x001f, 0x000f, 0x0007, 0x0003, 0x0001};
unsigned short U[] = {0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff,
0x8000, 0xc000, 0xe000, 0xf000, 0xf800, 0xfc00, 0xfe00, 0xff00,
0xff80, 0xffc0, 0xffe0, 0xfff0, 0xfff8, 0xfffc, 0xfffe, 0xffff};
unsigned short buf[192*16];
void clear(){
int i;
for (i=0; i<192*16; i++) buf[i]==0;
}
void render(){
int x,y;
for (y=0; y<192; y++){
for (x=0; x<256; x++) printf("%d", (buf[(y<<4)+(x>>4)]>>(15-(x&15)))&1);
printf("\n");
}
}
void drawline(int x1, int x2, int y){
int y_ = y<<4;
int x1_ = y_+(x1>>4);
int x2_ = y_+(x2>>4);
unsigned short *p = buf+x1_;
if (x1_==x2_){
*p|=T[x1]&U[x2];
return;
}
*p++|=T[x1];
switch (x2_-x1_){
case 14: *p++ = 0xffff;
case 13: *p++ = 0xffff;
case 12: *p++ = 0xffff;
case 11: *p++ = 0xffff;
case 10: *p++ = 0xffff;
case 9: *p++ = 0xffff;
case 8: *p++ = 0xffff;
case 7: *p++ = 0xffff;
case 6: *p++ = 0xffff;
case 5: *p++ = 0xffff;
case 4: *p++ = 0xffff;
case 3: *p++ = 0xffff;
case 2: *p++ = 0xffff;
case 1: *p++ = U[x2];
}
}
int main(){
int x,y;
clear();
for (y=0; y<192; y++){
drawline(y/2,y,y);
}
for (x=10; x<200; x+=6){
drawline(x,x+2,0);
drawline(x+3,x+5,1);
}
for (y=-49; y<50; y++){
x = sqrt(2500-y*y);
drawline(200-x, 200+x, y+60);
}
render();
return 0;
}