wyvern: a simple, typed, and pure object-oriented language

Wyvern: A Simple, Typed, and Pure Object-Oriented Language

Ligia Nistor, Darya Kurilova, Stephanie Balzer, Benjamin Chung, Alex Potanin, and Jonathan Aldrich

Carnegie Mellon University

© Darya Kurilova 2013

[MASPEGHI‘13, Montpellier, France]

1

World Wide Web •  Cross-‐Site Scrip-ng (XSS) •  Cross-‐Site Request

Forgery (CSRF) •  Injec-on A;acks •  Insecure Direct Object

References •  Broken Authen-ca-on

and Session Management •  … (OWASP 2013)

•  JavaScript •  Ruby on Rails •  Java •  Flash •  PHP •  Python •  CoffeeScript •  …

2 © Darya Kurilova 2013


World Wide Web

A web and mobile programming language that is

secure by default.



Wyvern •  Programming language:

–  For mobile and web programming

–  Secure by default



Target Characteristics Web programming Security

•  Pure object-oriented •  Interactive, value-

based •  Supporting functional

programming •  High-level •  Static typing •  Simple



Requirements for Pure OO •  State encapsulation •  Uniform access principle (Meyer) •  Interoperability and uniform treatment

(Cook)



Current State What Is There:

•  Specialization and generalization of types

•  A pure object-oriented model that supports reuse via composition mechanisms

What Is Missing:

•  A reuse mechanism, such as inheritance or delegation

•  A first-class, typed module system

•  Support for abstract type members



Next 1.  Wyvern Object Model 2.  Translating Classes to Objects 3.  Discussion: Reuse Mechanism for Wyvern



Object-Oriented Core of Wyvern 1   type Lot =



Object-Oriented Core of Wyvern 1   type Lot = 2   meth value : Int



Object-Oriented Core of Wyvern 1   type Lot = 2   meth value : Int 3   4   meth purchase(q : Int, p : Int) : Lot = 5   new



Object-Oriented Core of Wyvern 1   type Lot = 2   meth value : Int 3   4   meth purchase(q : Int, p : Int) : Lot = 5   new 6   var quantity : Int = q 7   var price : Int = p



Object-Oriented Core of Wyvern 1   type Lot = 2   meth value : Int 3   4   meth purchase(q : Int, p : Int) : Lot = 5   new 6   var quantity : Int = q 7   var price : Int = p 8   meth value : Int = 9   this.quantity * this.price



Object-Oriented Core of Wyvern 1   type Lot = 2   meth value : Int 3   4   meth purchase(q : Int, p : Int) : Lot = 5   new 6   var quantity : Int = q 7   var price : Int = p 8   meth value : Int = 9   this.quantity * this.price 10   11   val aLot = purchase(100, 100) 12   val value = aLot.value



Syntax of Object Oriented Core of Wyvern

•  Simple •  Support for functional

programming




•  State encapsulation •  Uniform access principle •  High-level •  Pure OO



Classes Are Not Essential

Cf. Self and JavaScript

…but they are convenient.

We believe classes should be syntactic sugar on top of a foundational object-oriented core.



Syntax of Object Oriented Core of Wyvern with Classes



Translating from



Translating to



Translating Classes

1   class Option

OO Wyvern with Classes



Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0




Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0 4   meth exercise : Int = ...




Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0 4   meth exercise : Int = ... 5   6   class var totalQuantityIssued : Int = 0




Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0 4   meth exercise : Int = ... 5   6   class var totalQuantityIssued : Int = 0 7   class meth issue(q : Int, 8   p : Int) : Option = 9   new




Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0 4   meth exercise : Int = ... 5   6   class var totalQuantityIssued : Int = 0 7   class meth issue(q : Int, 8   p : Int) : Option = 9   new 10   var quantity : Int = q 11   var price : Int = p




Translating Classes

1   class Option 2   var quantity : Int = 0 3   var price : Int = 0 4   meth exercise : Int = ... 5   6   class var totalQuantityIssued : Int = 0 7   class meth issue(q : Int, 8   p : Int) : Option = 9   new 10   var quantity : Int = q 11   var price : Int = p 12   13   var optn : Option = Option.issue(100, 50) 14   var ret : Int = optn.exercise




Translating Classes





Translating Classes


OO Wyvern OO Wyvern with Classes



Translating Classes


1   type Option = 2   meth exercise : Int




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new 9   var totalQuantityIssued : Int = 0




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new 9   var totalQuantityIssued : Int = 0 10   meth issue(q : Int, 11   p : Int) : Option = 12   new




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new 9   var totalQuantityIssued : Int = 0 10   meth issue(q : Int, 11   p : Int) : Option = 12   new 13   var quantity : Int = q 14   var price : Int = p




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new 9   var totalQuantityIssued : Int = 0 10   meth issue(q : Int, 11   p : Int) : Option = 12   new 13   var quantity : Int = q 14   var price : Int = p 15   meth exercise : Int = ...




Translating Classes


1   type Option = 2   meth exercise : Int 3   4   type OptionClass = 5   meth issue : Int -> Int -> Option 6   7   var Option : OptionClass = 8   new 9   var totalQuantityIssued : Int = 0 10   meth issue(q : Int, 11   p : Int) : Option = 12   new 13   var quantity : Int = q 14   var price : Int = p 15   meth exercise : Int = ... 16   17   var optn : Option = Option.issue(100, 50) 18   var ret : Int = optn.exercise




Discussion: Reuse Mechanism for Wyvern

Inheritance vs. Delegation

•  Inheritance is more suitable for classes, but they are not essential.

•  Is delegation more appropriate? •  Inheritance implemented via delegation?



A Delegation Scenario Object A: •  has method c() that has a reference to this

Object B: •  delegates to object A •  doesn’t have method c() •  calls method c()

What object should this in method c() refer to? •  e.g., in Self, this refers to object B •  if refers to object B, open recursion



Auxiliary Slides



Interoperability and Uniform Treatment

1   type Lot = 2   meth value : Int 3   meth compare(other : Lot) : Int




4   meth purchase1(q : Int, 5   p : Int) : Lot = 6   new 7   var quantity : Int = q 8   var price : Int = p 9   meth value : Int = ... 10   meth compare(l : Lot) : Int = 11   this.value – l.value

4   meth purchase2(q : Int, 5   p : Int) : Lot = 6   new 7   var quantity : Int = q + 10 8   var price : Int = p 9   meth value : Int = ... 10   meth compare(l : Lot) : Int = 11   this.value – l.value








12   val lot1 = purchase1(70, 50) 13   val lot2 = purchase2(40, 80) 14   val diff = lot1.compare(lot2)



Full Syntax of Object Oriented Core of Wyvern



Full Syntax of Object Oriented Core of Wyvern with Classes



wyvern: a simple, typed, and pure object-oriented language

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