add const index operator for vector classes

Author: markaren

include/threepp/math/Vector2.hpp

@@ -44,6 +44,8 @@ namespace threepp {
 
         float& operator[](unsigned int index);
 
+        float operator[](unsigned int index) const;
+
         Vector2& copy(const Vector2& v);
 
         Vector2& add(const Vector2& v);

include/threepp/math/Vector3.hpp

@@ -64,6 +64,8 @@ namespace threepp {
 
         float& operator[](size_t index);
 
+        float operator[](size_t index) const;
+
         Vector3& copy(const Vector3& v);
 
         // Adds v to this vector.

include/threepp/math/Vector4.hpp

@@ -26,6 +26,8 @@ namespace threepp {
 
         float& operator[](unsigned int index);
 
+        float operator[](unsigned int index) const;
+
         Vector4& set(float x, float y, float z, float w);
 
         Vector4& setScalar(float value);

src/threepp/math/Vector2.cpp

@@ -57,6 +57,18 @@ float& Vector2::operator[](unsigned int index) {
     }
 }
 
+float Vector2::operator[](unsigned int index) const {
+    if (index >= 2) throw std::runtime_error("index out of bounds: " + std::to_string(index));
+    switch (index) {
+        case 0:
+            return x;
+        case 1:
+            return y;
+        default:
+            throw std::runtime_error("index out of bound: " + std::to_string(index));
+    }
+}
+
 Vector2& Vector2::copy(const Vector2& v) {
 
     this->x = v.x;

src/threepp/math/Vector3.cpp

@@ -76,6 +76,19 @@ float& Vector3::operator[](size_t index) {
     }
 }
 
+float Vector3::operator[](size_t index) const {
+    switch (index) {
+        case 0:
+            return x;
+        case 1:
+            return y;
+        case 2:
+            return z;
+        default:
+            throw std::runtime_error("index out of bound: " + std::to_string(index));
+    }
+}
+
 Vector3& Vector3::copy(const Vector3& v) {
 
     this->x = v.x;

src/threepp/math/Vector4.cpp

@@ -30,6 +30,21 @@ float& Vector4::operator[](unsigned int index) {
     }
 }
 
+float Vector4::operator[](unsigned int index) const {
+    switch (index) {
+        case 0:
+            return x;
+        case 1:
+            return y;
+        case 2:
+            return z;
+        case 3:
+            return w;
+        default:
+            throw std::runtime_error("index out of bound: " + std::to_string(index));
+    }
+}
+
 Vector4& Vector4::set(float x, float y, float z, float w) {
 
     this->x = x;