tuple scalar operations

features/step_definitions/tuple.rb

@@ -107,3 +107,13 @@
   expected = Tuple.new(x: float, y: float2, z: float3, w: float4)
   assert_equal(@a.negate, expected)
 end
+
+Then('a * {float} = tuple\({float}, {float}, {float}, {float})') do |float, float1, float2, float3, float4|
+  expected = Tuple.new(x: float1, y: float2, z: float3, w: float4)
+  assert_equal(@a * float, expected)
+end
+
+Then('a \/ {float} = tuple\({float}, {float}, {float}, {float})') do |float, float1, float2, float3, float4|
+  expected = Tuple.new(x: float1, y: float2, z: float3, w: float4)
+  assert_equal(@a / float, expected)
+end

features/tuples.feature

@@ -55,18 +55,18 @@ Scenario: Negating a tuple
   Given a ← tuple(1, -2, 3, -4)
   Then -a = tuple(-1, 2, -3, 4)
 
-# Scenario: Multiplying a tuple by a scalar
-#   Given a ← tuple(1, -2, 3, -4)
-#   Then a * 3.5 = tuple(3.5, -7, 10.5, -14)
-# 
-# Scenario: Multiplying a tuple by a fraction
-#   Given a ← tuple(1, -2, 3, -4)
-#   Then a * 0.5 = tuple(0.5, -1, 1.5, -2)
-# 
-# Scenario: Dividing a tuple by a scalar
-#   Given a ← tuple(1, -2, 3, -4)
-#   Then a / 2 = tuple(0.5, -1, 1.5, -2)
-# 
+Scenario: Multiplying a tuple by a scalar
+  Given a ← tuple(1, -2, 3, -4)
+  Then a * 3.5 = tuple(3.5, -7, 10.5, -14)
+
+Scenario: Multiplying a tuple by a fraction
+  Given a ← tuple(1, -2, 3, -4)
+  Then a * 0.5 = tuple(0.5, -1, 1.5, -2)
+
+Scenario: Dividing a tuple by a scalar
+  Given a ← tuple(1, -2, 3, -4)
+  Then a / 2 = tuple(0.5, -1, 1.5, -2)
+
 # Scenario: Computing the magnitude of vector(1, 0, 0)
 #   Given v ← vector(1, 0, 0)
 #   Then magnitude(v) = 1

lib/tuple.rb

@@ -8,6 +8,14 @@ def initialize(x:, y:, z:, w:)
     @w = w
   end
 
+  def *(other)
+    Tuple.new(x: @x * other, y: @y * other, z: @z * other, w: @w * other)
+  end
+
+  def /(other)
+    Tuple.new(x: @x / other, y: @y / other, z: @z / other, w: @w / other)
+  end
+
   def +(other)
     Tuple.new(x: @x + other.x, y: @y + other.y, z: @z + other.z, w: @w + other.w)
   end

sig/lib/tuple.rbs

@@ -7,6 +7,8 @@ class Tuple
   def z: -> Float
   def w: -> Float
   def initialize: (x: Float, y: Float, z: Float, w: Float) -> void
+  def *: (Float) -> Tuple
+  def /: (Float) -> Tuple
   def +: (Tuple) -> Tuple
   def -: (Tuple) -> Tuple
   def negate: -> Tuple