tasks a-s

Task/Numeric-error-propagation/Ruby/numeric-error-propagation.rb

@@ -0,0 +1,64 @@
+class NumberWithUncertainty
+  def initialize(number, error)
+    @num = number
+    @err = error.abs
+  end
+  attr_reader :num, :err
+
+  def +(other)
+    if other.kind_of?(self.class)
+      self.class.new(num + other.num, Math::hypot(err, other.err))
+    else
+      self.class.new(num + other, err)
+    end
+  end
+
+  def -(other)
+    if other.kind_of?(self.class)
+      self.class.new(num - other.num, Math::hypot(err, other.err))
+    else
+      self.class.new(num - other, err)
+    end
+  end
+
+  def *(other)
+    if other.kind_of?(self.class)
+      prod = num * other.num
+      e = Math::hypot((prod * err / num), (prod * other.err / other.num))
+      self.class.new(prod, e)
+    else
+      self.class.new(num * other, (err * other).abs)
+    end
+  end
+
+  def /(other)
+    if other.kind_of?(self.class)
+      quo = num / other.num
+      e = Math::hypot((quo * err / num), (quo * other.err / other.num))
+      self.class.new(quo, e)
+    else
+      self.class.new(num / other, (err * other).abs)
+    end
+  end
+
+  def **(exponent)
+    Float(exponent) rescue raise ArgumentError, "not an number: #{exponent}"
+    prod = num ** exponent
+    self.class.new(prod, (prod * exponent * err / num).abs)
+  end
+
+  def sqrt
+    self ** 0.5
+  end
+
+  def to_s
+    "#{num} \u00b1 #{err}"
+  end
+end
+
+x1 = NumberWithUncertainty.new(100, 1.1)
+y1 = NumberWithUncertainty.new( 50, 1.2)
+x2 = NumberWithUncertainty.new(200, 2.2)
+y2 = NumberWithUncertainty.new(100, 2.3)
+
+puts ((x1 - x2) ** 2 + (y1 - y2) ** 2).sqrt