Experiences with an Object-Oriented, Multi-Stage Language
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Scala Tutorial
Scala Tutorial SCALA TUTORIAL Simply Easy Learning by tutorialspoint.com tutorialspoint.com i ABOUT THE TUTORIAL Scala Tutorial Scala is a modern multi-paradigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way. Scala has been created by Martin Odersky and he released the first version in 2003. Scala smoothly integrates features of object-oriented and functional languages. This tutorial gives a great understanding on Scala. Audience This tutorial has been prepared for the beginners to help them understand programming Language Scala in simple and easy steps. After completing this tutorial, you will find yourself at a moderate level of expertise in using Scala from where you can take yourself to next levels. Prerequisites Scala Programming is based on Java, so if you are aware of Java syntax, then it's pretty easy to learn Scala. Further if you do not have expertise in Java but you know any other programming language like C, C++ or Python, then it will also help in grasping Scala concepts very quickly. Copyright & Disclaimer Notice All the content and graphics on this tutorial are the property of tutorialspoint.com. Any content from tutorialspoint.com or this tutorial may not be redistributed or reproduced in any way, shape, or form without the written permission of tutorialspoint.com. Failure to do so is a violation of copyright laws. This tutorial may contain inaccuracies or errors and tutorialspoint provides no guarantee regarding the accuracy of the site or its contents including this tutorial. If you discover that the tutorialspoint.com site or this tutorial content contains some errors, please contact us at [email protected] TUTORIALS POINT Simply Easy Learning Table of Content Scala Tutorial .......................................................................... -
1 Aliasing and Immutability
Vocabulary: Accessors & Mutators Computer Science and Engineering The Ohio State University Accessor: A method that reads, but never changes, the Aliasing and Immutability (abstract) state of an object Computer Science and Engineering College of Engineering The Ohio State University Concrete representation may change, so long as change is not visible to client eg Lazy initialization Examples: getter methods, toString Lecture 8 Formally: restores “this” Mutator method: A method that may change the (abstract) state of an object Examples: setter methods Formally: updates “this” Constructors not considered mutators A Fixed Epoch Interface A Broken Time Period Class Computer Science and Engineering The Ohio State University Computer Science and Engineering The Ohio State University // Interface cover story goes here public class Period implements FixedEpoch { // Mathematical modeling … private Date start; // constructor private Date end; // requires start date < end date // initializes start and end dates // operations have specifications based on the model public Period(Date start, Date end) { // exercises … this.start = start; this.e nd = e nd; public interface FixedEpoch { } public Date getStart(); public Date getEnd(); } public Date getStart() { return start; } public Date getEnd() { return end; } } Problem: Aliasing A Better Period Class Computer Science and Engineering The Ohio State University Computer Science and Engineering The Ohio State University Assignment in constructor creates an alias public class Period -
Functional Programming Inside OOP?
Functional Programming inside OOP? It’s possible with Python >>>whoami() Carlos Villavicencio ● Ecuadorian θ ● Currently: Python & TypeScript ● Community leader ● Martial arts: 剣道、居合道 ● Nature photography enthusiast po5i Cayambe Volcano, 2021. >>>why_functional_programming ● Easier and efficient ● Divide and conquer ● Ease debugging ● Makes code simpler and readable ● Also easier to test >>>history() ● Functions were first-class objects from design. ● Users wanted more functional solutions. ● 1994: map, filter, reduce and lambdas were included. ● In Python 2.2, lambdas have access to the outer scope. “Not having the choice streamlines the thought process.” - Guido van Rossum. The fate of reduce() in Python 3000 https://python-history.blogspot.com/2009/04/origins-of-pythons-functional-features.html >>>has_django_fp() https://github.com/django/django/blob/46786b4193e04d398532bbfc3dcf63c03c1793cb/django/forms/formsets.py#L201-L213 https://github.com/django/django/blob/ca9872905559026af82000e46cde6f7dedc897b6/django/forms/formsets.py#L316-L328 Immutability An immutable object is an object whose state cannot be modified after it is created. Booleans, strings, and integers are immutable objects. List and dictionaries are mutable objects. Thread safety >>>immutability def update_list(value: list) -> None: def update_number(value: int) -> None: value += [10] value += 10 >>> foo = [1, 2, 3] >>> foo = 10 >>> id(foo) >>> update_number(foo) 4479599424 >>> foo >>> update_list(foo) 10 >>> foo 樂 [1, 2, 3, 10] >>> id(foo) 4479599424 >>>immutability def update_number(value: int) -> None: print(value, id(value)) value += 10 print(value, id(value)) >>> foo = 10 >>> update_number(foo) 10 4478220880 ڃ 4478221200 20 >>> foo 10 https://medium.com/@meghamohan/mutable-and-immutable-side-of-python-c2145cf72747 Decorators They are functions which modify the functionality of other functions. Higher order functions. -
Assignment 6: Subtyping and Bidirectional Typing
Assignment 6: Subtyping and Bidirectional Typing 15-312: Foundations of Programming Languages Joshua Dunfield ([email protected]) Out: Thursday, October 24, 2002 Due: Thursday, November 7 (11:59:59 pm) 100 points total + (up to) 20 points extra credit 1 Introduction In this assignment, you will implement a bidirectional typechecker for MinML with , , +, 1, 0, , , and subtyping with base types int and float. ! ∗ 8 9 Note: In the .sml files, most changes from Assignment 4 are indicated like this: (* new asst6 code: *) ... (* end asst6 code *) 2 New in this assignment Some things have become obsolete (and have either been removed or left • in a semi-supported state). Exceptions and continuations are no longer “officially” supported. One can now (and sometimes must!) write type annotations e : τ. The • abstract syntax constructor is called Anno. The lexer supports shell-style comments in .mml source files: any line • beginning with # is ignored. There are now two valid syntaxes for functions, the old syntax fun f (x:t1):t2 is e end • and a new syntax fun f(x) is e end. Note the lack of type anno- tations. The definition of the abstract syntax constructor Fun has been changed; its arguments are now just bindings for f and x and the body. It no longer takes two types. 1 The old syntax fun f(x:t1):t2 is e end is now just syntactic sugar, transformed by the parser into fun f(x) is e end : t1 -> t2. There are floating point numbers, written as in SML. There is a new set of • arithmetic operators +., -., *., ˜. -
Enforcing Abstract Immutability
Enforcing Abstract Immutability by Jonathan Eyolfson A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Doctor of Philosophy in Electrical and Computer Engineering Waterloo, Ontario, Canada, 2018 © Jonathan Eyolfson 2018 Examining Committee Membership The following served on the Examining Committee for this thesis. The decision of the Examining Committee is by majority vote. External Examiner Ana Milanova Associate Professor Rensselaer Polytechnic Institute Supervisor Patrick Lam Associate Professor University of Waterloo Internal Member Lin Tan Associate Professor University of Waterloo Internal Member Werner Dietl Assistant Professor University of Waterloo Internal-external Member Gregor Richards Assistant Professor University of Waterloo ii I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. iii Abstract Researchers have recently proposed a number of systems for expressing, verifying, and inferring immutability declarations. These systems are often rigid, and do not support “abstract immutability”. An abstractly immutable object is an object o which is immutable from the point of view of any external methods. The C++ programming language is not rigid—it allows developers to express intent by adding immutability declarations to methods. Abstract immutability allows for performance improvements such as caching, even in the presence of writes to object fields. This dissertation presents a system to enforce abstract immutability. First, we explore abstract immutability in real-world systems. We found that developers often incorrectly use abstract immutability, perhaps because no programming language helps developers correctly implement abstract immutability. -
Exploring Language Support for Immutability
Exploring Language Support for Immutability Michael Coblenz∗, Joshua Sunshine∗, Jonathan Aldrich∗, Brad Myers∗, Sam Webery, Forrest Shully May 8, 2016 CMU-ISR-16-106 This is an extended version of a paper that was published at ICSE [11]. Institute for Software Research School of Computer Science Carnegie Mellon University Pittsburgh, PA 15213 ∗School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA ySoftware Engineering Institute, Carnegie Mellon University, Pittsburgh, PA, USA This material is supported in part by NSA lablet contract #H98230-14-C-0140, by NSF grant CNS-1423054, and by Contract No. FA8721-05-C-0003 with CMU for the operation of the SEI, a federally funded research and development center sponsored by the US DoD. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of any of the sponsors. Keywords: Programming language design, Programming language usability, Immutability, Mutability, Program- mer productivity, Empirical studies of programmers Abstract Programming languages can restrict state change by preventing it entirely (immutability) or by restricting which clients may modify state (read-only restrictions). The benefits of immutability and read-only restrictions in software structures have been long-argued by practicing software engineers, researchers, and programming language designers. However, there are many proposals for language mechanisms for restricting state change, with a remarkable diversity of tech- niques and goals, and there is little empirical data regarding what practicing software engineers want in their tools and what would benefit them. We systematized the large collection of techniques used by programming languages to help programmers prevent undesired changes in state. -
(901133) Instructor: Eng
home Al-Albayt University Computer Science Department C++ Programming 1 (901133) Instructor: Eng. Rami Jaradat [email protected] 1 home Subjects 1. Introduction to C++ Programming 2. Control Structures 3. Functions 4. Arrays 5. Pointers 6. Strings 2 home 1 - Introduction to C++ Programming 3 home What is computer? • Computers are programmable devices capable of performing computations and making logical decisions. • Computers can store, retrieve, and process data according to a list of instructions • Hardware is the physical part of the compute: keyboard, screen, mouse, disks, memory, and processing units • Software is a collection of computer programs, procedures and documentation that perform some tasks on a computer system 4 home Computer Logical Units • Input unit – obtains information (data) from input devices • Output unit – outputs information to output device or to control other devices. • Memory unit – Rapid access, low capacity, stores information • Secondary storage unit – cheap, long-term, high-capacity storage, stores inactive programs • Arithmetic and logic unit (ALU) – performs arithmetic calculations and logic decisions • Central processing unit (CPU): – supervises and coordinates the other sections of the computer 5 home Computer language • Machine languages: machine dependent, it consists of strings of numbers giving machine specific instructions: +1300042774 +1400593419 +1200274027 • Assembly languages: English-like abbreviations representing elementary operations, assemblers convert assembly language to machine -
1 Immutable Classes
A Broken Time Period Class Computer Science and Engineering The Ohio State University public class Period { private Date start; Immutable Classes private Date end; Computer Science and Engineering College of Engineering The Ohio State University public Period(Date start, Date end) { assert (start.compareTo(end) > 0); //start < end this.start = start; this.end = end; Lecture 8 } public Date getStart() { return start; } public Date getEnd() { return end; } } Questions Problem: Aliasing Computer Science and Engineering The Ohio State University Computer Science and Engineering The Ohio State University What is an invariant in general? Assignment in constructor creates an alias Ans: Client and component both have references to the same Date object Class invariant can be undermined via alias What is an invariant for class Period? Date start = new Date(300); Ans: Date end = new Date (500); Period p = new Period (start, end); end.setTime(100); //modifies internals of p Why is this an invariant for this class? Solution: “defensive copying” Ans: Constructor creates a copy of the arguments Copy is used to initialize the private fields Metaphor: ownership A Better Period Class Good Practice: Copy First Computer Science and Engineering The Ohio State University Computer Science and Engineering The Ohio State University public class Period { private Date start; When making a defensive copy of private Date end; constructor arguments: public Period(Date start, Date end) { First copy the arguments assert (start.compareTo(end) > -
Explicitly Implicifying Explicit Constructors
Explicitly Implicifying explicit Constructors Document number: P1163R0 Date: 2018-08-31 Project: Programming Language C++, Library Working Group Reply-to: Nevin “☺” Liber, [email protected] or [email protected] Table of Contents Revision History ................................................................................................................ 3 P11630R0 .................................................................................................................................... 3 Introduction ....................................................................................................................... 4 Motivation and Scope ....................................................................................................... 5 Impact On the Standard ................................................................................................... 6 Policy .................................................................................................................................. 7 Design Decisions ................................................................................................................ 8 Technical Specifications ................................................................................................... 9 [template.bitset]........................................................................................................................ 10 [bitset.cons] .............................................................................................................................. -
Adding Crucial Features to a Typestate-Oriented Language
João Daniel da Luz Mota Bachelor in Computer Science and Engineering Coping with the reality: adding crucial features to a typestate-oriented language Dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science in Computer Science and Engineering Adviser: António Maria Lobo César Alarcão Ravara, Associate Professor, NOVA School of Science and Technology Co-adviser: Marco Giunti, Researcher, NOVA School of Science and Technology Examination Committee Chair: Hervé Miguel Cordeiro Paulino, Associate Professor, NOVA School of Science and Technology Rapporteur: Ornela Dardha, Lecturer, School of Computing Science, University of Glasgow Members: António Maria Lobo César Alarcão Ravara Marco Giunti February, 2021 Coping with the reality: adding crucial features to a typestate-oriented lan- guage Copyright © João Daniel da Luz Mota, NOVA School of Science and Technology, NOVA University Lisbon. The NOVA School of Science and Technology and the NOVA University Lisbon have the right, perpetual and without geographical boundaries, to file and publish this dissertation through printed copies reproduced on paper or on digital form, or by any other means known or that may be invented, and to disseminate through scientific repositories and admit its copying and distribution for non-commercial, educational or research purposes, as long as credit is given to the author and editor. Acknowledgements Throughout the writing of this thesis I have received a great deal of support and assis- tance. I would first like to thank my adviser, Professor António Ravara, and co-adviser, Re- searcher Marco Giunti, for the guidance and direction provided. Your feedback was crucial and allowed me to organize my work and write this thesis. -
The Cool Reference Manual∗
The Cool Reference Manual∗ Contents 1 Introduction 3 2 Getting Started 3 3 Classes 4 3.1 Features . 4 3.2 Inheritance . 5 4 Types 6 4.1 SELF TYPE ........................................... 6 4.2 Type Checking . 7 5 Attributes 8 5.1 Void................................................ 8 6 Methods 8 7 Expressions 9 7.1 Constants . 9 7.2 Identifiers . 9 7.3 Assignment . 9 7.4 Dispatch . 10 7.5 Conditionals . 10 7.6 Loops . 11 7.7 Blocks . 11 7.8 Let . 11 7.9 Case . 12 7.10 New . 12 7.11 Isvoid . 12 7.12 Arithmetic and Comparison Operations . 13 ∗Copyright c 1995-2000 by Alex Aiken. All rights reserved. 1 8 Basic Classes 13 8.1 Object . 13 8.2 IO ................................................. 13 8.3 Int................................................. 14 8.4 String . 14 8.5 Bool . 14 9 Main Class 14 10 Lexical Structure 14 10.1 Integers, Identifiers, and Special Notation . 15 10.2 Strings . 15 10.3 Comments . 15 10.4 Keywords . 15 10.5 White Space . 15 11 Cool Syntax 17 11.1 Precedence . 17 12 Type Rules 17 12.1 Type Environments . 17 12.2 Type Checking Rules . 18 13 Operational Semantics 22 13.1 Environment and the Store . 22 13.2 Syntax for Cool Objects . 24 13.3 Class definitions . 24 13.4 Operational Rules . 25 14 Acknowledgements 30 2 1 Introduction This manual describes the programming language Cool: the Classroom Object-Oriented Language. Cool is a small language that can be implemented with reasonable effort in a one semester course. Still, Cool retains many of the features of modern programming languages including objects, static typing, and automatic memory management. -
Generic Immutability and Nullity Types for an Imperative Object-Oriented Programming Language with flexible Initialization
Generic Immutability and Nullity Types for an imperative object-oriented programming language with flexible initialization James Elford June 21, 2012 Abstract We present a type system for parametric object mutability and ref- erence nullity in an imperative object oriented language. We present a simple but powerful system for generic nullity constraints, and build on previous work to provide safe initialization of objects which is not bound to constructors. The system is expressive enough to handle initialization of cyclic immutable data structures, and to enforce their cyclic nature through the type system. We provide the crucial parts of soundness ar- guments (though the full proof is not yet complete). Our arguments are novel, in that they do not require auxiliary runtime constructs (ghost state) in order to express or demonstrate our desired properties. 2 Contents 1 Introduction 4 1.1 In this document . .5 2 Background 6 2.1 Parametric Types . .6 2.1.1 Static Polymorphism through Templates . .7 2.1.2 Static Polymorphism through Generic Types . 12 2.2 Immutability . 18 2.2.1 Immutability in C++ .................... 19 2.2.2 Immutability in Java and C# ............... 21 2.2.3 An extension to Java's immutability model . 21 2.2.4 Parametric Immutability Constraints . 24 2.3 IGJ: Immutability Generic Java .................. 25 2.4 Nullity . 27 2.5 Areas of commonality . 30 3 Goals 32 4 Existing systems in more detail 34 4.1 The initialization problem . 34 4.2 What do we require from initialization? . 35 4.3 Approaches to initialization . 37 4.4 Delay Types and initialization using stack-local regions .