vector.c

// compiles with
// 	gcc vector.c -Wall -Wextra -Wpedantic `sdl2-config --cflags --libs` -lm

#include <SDL.h>
#include <math.h>

const double PI = 3.14159265358979323846264338327950288;

typedef struct {
  double x, y;
} vec2;

double rad2deg(double rad) { return rad * (180 / PI); }

double deg2rad(double deg) { return deg / (180 / PI); }

void vec2_print(vec2 v) { SDL_Log("(%.2f, %.2f)", v.x, v.y); }

vec2 vec2_add(vec2 a, vec2 b) { return (vec2){a.x + b.x, a.y + b.y}; }

float vec2_length(vec2 v) { return sqrtf(v.x * v.x + v.y * v.y); }

vec2 vec2_normalized(const vec2 v) {
  double length = vec2_length(v);
  return (vec2){v.x / length, v.y / length};
}

double vec2_rotation(const vec2 v) {
  double rad = atan2f(v.x, v.y);
  return rad2deg(rad);
}

vec2 vec2_rotated(const vec2 v, double angle) {
  double rad = deg2rad(angle);
  vec2 temp;
  temp.x = cos(rad) * v.x - sin(rad) * v.y;
  temp.y = sin(rad) * v.x + cos(rad) * v.y;
  return temp;
}

int main() {
  vec2 p1 = {1, 1};
  vec2_print(p1);
  SDL_Log("%f", vec2_length(p1));
  SDL_Log("%f", vec2_rotation(p1));

  SDL_Log(" ");

  vec2 p2 = vec2_normalized(vec2_rotated(p1, 90));
  vec2_print(p2);
  SDL_Log("%f", vec2_length(p2));
  SDL_Log("%f", vec2_rotation(p2));

  return 0;
}