diff --git a/vec2d.h b/vec2d.h
index 1c6a3e8..b5bbc79 100644
--- a/vec2d.h
+++ b/vec2d.h
@@ -2,73 +2,78 @@
 #define VEC2D_H_INCLUDED
 
 #include <cmath>
+#include <ostream>
 
 class vec2d {
-public:
+  public:
     double x;
     double y;
 
-    vec2d & operator = (const vec2d & other) {
-	x = other.x;
-	y = other.y;
-	return *this;
+    vec2d& operator=(const vec2d& other) {
+        x = other.x;
+        y = other.y;
+        return *this;
     }
 
-    vec2d & operator += (const vec2d & other) {
-	x += other.x;
-	y += other.y;
-	return *this;
+    vec2d& operator+=(const vec2d& other) {
+        x += other.x;
+        y += other.y;
+        return *this;
     }
 
-    vec2d & operator -= (const vec2d & other) {
-	x -= other.x;
-	y -= other.y;
-	return *this;
+    vec2d& operator-=(const vec2d& other) {
+        x -= other.x;
+        y -= other.y;
+        return *this;
     }
 
-    vec2d & operator *= (double l) {
-	x *= l;
-	y *= l;
-	return *this;
+    vec2d& operator*=(double l) {
+        x *= l;
+        y *= l;
+        return *this;
     }
 
-    vec2d operator + (const vec2d & other) const {
-	return vec2d{x + other.x, y + other.y};
+    vec2d operator+(const vec2d& other) const {
+        return vec2d{x + other.x, y + other.y};
     }
 
-    vec2d operator - (const vec2d & other) const {
-	return vec2d{x - other.x, y - other.y};
+    vec2d operator-(const vec2d& other) const {
+        return vec2d{x - other.x, y - other.y};
     }
 
-    vec2d operator * (double l) const {
-	return vec2d{x*l, y*l};
+    vec2d operator*(double l) const {
+        return vec2d{x * l, y * l};
     }
 
-    vec2d operator / (double a) const {
-	return vec2d{x/a, y/a};
+    vec2d operator/(double a) const {
+        return vec2d{x / a, y / a};
     }
 
-    vec2d & rotate (double angle) {
-	double sin_a = sin(angle);
-	double cos_a = cos(angle);
-	double x1 = x;
-	double y1 = y;
-	x = cos_a*x1 - sin_a*y1;
-	y = sin_a*x1 + cos_a*y1;
-	return *this;
+    vec2d& rotate(double angle) {
+        double sin_a = sin(angle);
+        double cos_a = cos(angle);
+        double x1 = x;
+        double y1 = y;
+        x = cos_a * x1 - sin_a * y1;
+        y = sin_a * x1 + cos_a * y1;
+        return *this;
     }
 
-    static double dot (const vec2d & a, const vec2d & b) {
-	return a.x*b.x + a.y*b.y;
+    static double dot(const vec2d& a, const vec2d& b) {
+        return a.x * b.x + a.y * b.y;
     }
 
-    static double cross (const vec2d & a, const vec2d & b) {
-	return a.x*b.x + a.y*b.y;
+    static double cross(const vec2d& a, const vec2d& b) {
+        return a.x * b.x + a.y * b.y;
     }
 };
 
-static inline vec2d operator * (double l, const vec2d & v) {
-    return vec2d{v.x*l, v.y*l};
+static inline std::ostream& operator<<(std::ostream& os, vec2d& p) {
+    return os << '(' << p.x << ", " << p.y << ')';
+}
+
+static inline vec2d operator*(double l, const vec2d& v) {
+    return vec2d{v.x * l, v.y * l};
 }
 
 #endif