sapphire-lang 0.8.0

Gradually typed scripting language where every value is an object and types are optional, checked at runtime
Documentation 
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# classes.spr — class definitions, fields, methods, inheritance, super

class Shape {
  attr color = "red"

  def describe {
    "A #{self.color} shape"
  }

  def area {
    0
  }
}

class Rectangle < Shape {
  attr width: Int
  attr height: Int

  def area {
    self.width * self.height
  }

  def describe {
    super + " (rectangle #{self.width}x#{self.height})"
  }
}

class Circle < Shape {
  attr radius: Int

  def area {
    # integer approximation
    3 * self.radius * self.radius
  }

  def describe {
    super + " (circle r=#{self.radius})"
  }
}

r = Rectangle.new(width: 4, height: 5)
print r.describe
print "Area: #{r.area}"

c = Circle.new(color: "blue", radius: 3)
print c.describe
print "Area: #{c.area}"

# Field mutation via methods
class Counter {
  attr n = 0

  def inc {
    self.n = self.n + 1
  }

  def reset {
    self.n = 0
  }

  def value {
    self.n
  }
}

counter = Counter.new
counter.inc
counter.inc
counter.inc
print "Counter: #{counter.value}"
counter.reset
print "After reset: #{counter.value}"

# is_a? type checking
print r.is_a?(Rectangle)
print r.is_a?(Shape)
print r.is_a?(Circle)