Functional Programming at Work in Object-Oriented Programming
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Lecture 4. Higher-Order Functions Functional Programming
Lecture 4. Higher-order functions Functional Programming [Faculty of Science Information and Computing Sciences] 0 I function call and return as only control-flow primitive I no loops, break, continue, goto I (almost) unique types I no inheritance hell I high-level declarative data-structures I no explicit reference-based data structures Goal of typed purely functional programming Keep programs easy to reason about by I data-flow only through function arguments and return values I no hidden data-flow through mutable variables/state [Faculty of Science Information and Computing Sciences] 1 I (almost) unique types I no inheritance hell I high-level declarative data-structures I no explicit reference-based data structures Goal of typed purely functional programming Keep programs easy to reason about by I data-flow only through function arguments and return values I no hidden data-flow through mutable variables/state I function call and return as only control-flow primitive I no loops, break, continue, goto [Faculty of Science Information and Computing Sciences] 1 I high-level declarative data-structures I no explicit reference-based data structures Goal of typed purely functional programming Keep programs easy to reason about by I data-flow only through function arguments and return values I no hidden data-flow through mutable variables/state I function call and return as only control-flow primitive I no loops, break, continue, goto I (almost) unique types I no inheritance hell [Faculty of Science Information and Computing Sciences] 1 Goal -
Functional Languages
Functional Programming Languages (FPL) 1. Definitions................................................................... 2 2. Applications ................................................................ 2 3. Examples..................................................................... 3 4. FPL Characteristics:.................................................... 3 5. Lambda calculus (LC)................................................. 4 6. Functions in FPLs ....................................................... 7 7. Modern functional languages...................................... 9 8. Scheme overview...................................................... 11 8.1. Get your own Scheme from MIT...................... 11 8.2. General overview.............................................. 11 8.3. Data Typing ...................................................... 12 8.4. Comments ......................................................... 12 8.5. Recursion Instead of Iteration........................... 13 8.6. Evaluation ......................................................... 14 8.7. Storing and using Scheme code ........................ 14 8.8. Variables ........................................................... 15 8.9. Data types.......................................................... 16 8.10. Arithmetic functions ......................................... 17 8.11. Selection functions............................................ 18 8.12. Iteration............................................................. 23 8.13. Defining functions ........................................... -
The Future of Embedded Software
The Future of Embedded Software Edward A. Lee Professor, Chair of EE, and Associate Chair of EECS UC Berkeley ARTEMIS 2006 Annual Conference Graz, Austria May 22-24, 2006 Why Embedded Software? Why Now? “Information technology (IT) is on the verge of another revolution. Driven by the increasing capabilities and ever declining costs of computing and communications devices, IT is being embedded into a growing range of physical devices linked together through networks and will become ever more pervasive as the component technologies become smaller, faster, and cheaper... These networked systems of embedded computers ... have the potential to change radically the way people interact with their environment by linking together a range of devices and sensors that will allow information to be collected, shared, and processed in unprecedented ways. ... The use of [these embedded computers] throughout society could well dwarf previous milestones in the information revolution.” National Research Council Report Embedded Everywhere Lee, Berkeley 2 The Key Obstacle to Progress: Gap Between Systems and Computing | Traditional dynamic systems theory needs to adapt to better account for the behavior of software and networks. | Traditional computer science needs to adapt to embrace time, concurrency, and the continuum of physical processes. Lee, Berkeley 3 The Next Systems Theory: Simultaneously Physical and Computational The standard model: Embedded software is software on small computers. The technical problem is one of optimization (coping with limited resources). The Berkeley model: Embedded software is software integrated with physical processes. The technical problem is managing time and concurrency in computational systems. Lee, Berkeley 4 Obstacles in Today’s Technology: Consider Real Time Electronics Technology Delivers Timeliness… … and the overlaying software abstractions discard it. -
Higher-Order Functions 15-150: Principles of Functional Programming – Lecture 13
Higher-order Functions 15-150: Principles of Functional Programming { Lecture 13 Giselle Reis By now you might feel like you have a pretty good idea of what is going on in functional program- ming, but in reality we have used only a fragment of the language. In this lecture we see what more we can do and what gives the name functional to this paradigm. Let's take a step back and look at ML's typing system: we have basic types (such as int, string, etc.), tuples of types (t*t' ) and functions of a type to a type (t ->t' ). In a grammar style (where α is a basic type): τ ::= α j τ ∗ τ j τ ! τ What types allowed by this grammar have we not used so far? Well, we could, for instance, have a function below a tuple. Or even a function within a function, couldn't we? The following are completely valid types: int*(int -> int) int ->(int -> int) (int -> int) -> int The first one is a pair in which the first element is an integer and the second one is a function from integers to integers. The second one is a function from integers to functions (which have type int -> int). The third type is a function from functions to integers. The two last types are examples of higher-order functions1, i.e., a function which: • receives a function as a parameter; or • returns a function. Functions can be used like any other value. They are first-class citizens. Maybe this seems strange at first, but I am sure you have used higher-order functions before without noticing it. -
Capturing Interactions in Architectural Patterns
Capturing Interactions in Architectural Patterns Dharmendra K Yadav Rushikesh K Joshi Department of Computer Science and Engineering Department of Computer Science and Engineering Indian Institute of Technology Bombay Indian Institute of Technology Bombay Powai, Mumbai 400076, India Powai, Mumbai 400076, India Email: [email protected] Email: [email protected] TABLE I Abstract—Patterns of software architecture help in describing ASUMMARY OF CCS COMBINATORS structural and functional properties of the system in terms of smaller components. The emphasis of this work is on capturing P rimitives & Descriptions Architectural the aspects of pattern descriptions and the properties of inter- Examples Significance component interactions including non-deterministic behavior. Prefix (.) Action sequence intra-component Through these descriptions we capture structural and behavioral p1.p2 sequential flow specifications as well as properties against which the specifications Summation (+) Nondeterminism choice within a component are verified. The patterns covered in this paper are variants of A1 + A2 Proxy, Chain, MVC, Acceptor-Connector, Publisher-Subscriber Composition (|) Connect matching multiple connected and Dinning Philosopher patterns. While the machines are CCS- A1 | A2 i/o ports in assembly components based, the properties have been described in Modal µ-Calculus. Restriction (\) Hiding ports from Internal The approach serves as a framework for precise architectural A\{p1, k1, ..} further composition features descriptions. Relabeling ([]) Renaming of ports syntactic renaming A[new/old, ..] I. INTRODUCTION In component/connector based architectural descriptions [6], [13], components are primary entities having identities in the represents interface points as ports uses a subset of CSP for system and connectors provide the means for communication it’s formal semantics. -
Automatic Verification of Java Design Patterns
Automatic Verification of Java Design Patterns Alex Blewitt, Alan Bundy, Ian Stark Division of Informatics, University of Edinburgh 80 South Bridge, Edinburgh EH1 1HN, UK [email protected] [email protected] [email protected] Abstract 2. Design patterns There are a number of books which catalogue and de- Design patterns are widely used by object oriented de- scribe design patterns [4, 1, 6] including an informal de- signers and developers for building complex systems in ob- scription of the key features and examples of their use. ject oriented programming languages such as Java. How- However, at the moment there are no books which attempt ever, systems evolve over time, increasing the chance that to formalise these descriptions, possibly for the following the pattern in its original form will be broken. reasons: We attempt to show that many patterns (implemented in Java) can be verified automatically. Patterns are defined 1. The implementation (and description) of the pattern is in terms of variants, mini-patterns, and constraints in a language-specific. pattern description language called SPINE. These specifi- 2. There are often several ways to implement a pattern cations are then processed by HEDGEHOG, an automated within the same language. proof tool that attempts to prove that Java source code 3. Formal language descriptions are not common within meets these specifications. the object oriented development community. Instead, each pattern is presented as a brief description, and an example of its implementation and use. Designers and developers are then expected to learn the ‘feel’ of a pat- 1. -
The Machine That Builds Itself: How the Strengths of Lisp Family
Khomtchouk et al. OPINION NOTE The Machine that Builds Itself: How the Strengths of Lisp Family Languages Facilitate Building Complex and Flexible Bioinformatic Models Bohdan B. Khomtchouk1*, Edmund Weitz2 and Claes Wahlestedt1 *Correspondence: [email protected] Abstract 1Center for Therapeutic Innovation and Department of We address the need for expanding the presence of the Lisp family of Psychiatry and Behavioral programming languages in bioinformatics and computational biology research. Sciences, University of Miami Languages of this family, like Common Lisp, Scheme, or Clojure, facilitate the Miller School of Medicine, 1120 NW 14th ST, Miami, FL, USA creation of powerful and flexible software models that are required for complex 33136 and rapidly evolving domains like biology. We will point out several important key Full list of author information is features that distinguish languages of the Lisp family from other programming available at the end of the article languages and we will explain how these features can aid researchers in becoming more productive and creating better code. We will also show how these features make these languages ideal tools for artificial intelligence and machine learning applications. We will specifically stress the advantages of domain-specific languages (DSL): languages which are specialized to a particular area and thus not only facilitate easier research problem formulation, but also aid in the establishment of standards and best programming practices as applied to the specific research field at hand. DSLs are particularly easy to build in Common Lisp, the most comprehensive Lisp dialect, which is commonly referred to as the “programmable programming language.” We are convinced that Lisp grants programmers unprecedented power to build increasingly sophisticated artificial intelligence systems that may ultimately transform machine learning and AI research in bioinformatics and computational biology. -
The Command Dispatcher Pattern Benoit Dupire and Eduardo B Fernandez {[email protected], [email protected]}
The Command Dispatcher Pattern Benoit Dupire and Eduardo B Fernandez {[email protected], [email protected]} Department of Computer Science and Engineering. Florida Atlantic University Boca Raton, FL 33431 Can also be called: Command Evaluator Pattern. Intent This pattern increases the flexibility of applications by enabling their services to be changed, by adding, replacing or removing any command handlers at any point in time without having to modify, recompile or statically relink the application. By simulating the command-evaluation feature common in interpreted languages, this pattern supports the need for continual, incremental evolution of applications. Example Autonomous Underwater Vehicles (AUVs) are small, unmanned, untethered submersibles. There are numerous applications for AUVs, such as oceanographic surveys, operations in hazardous environments, underwater structure inspection and military operations. We implement the high level controller of this AUV as a Hierarchical Finite State Machine (Figure 1). A state of the Finite State Machine (FSM) represents a mode of the system, in which some tasks have to be executed, as described in the mission plan. The system takes transitions based on the results of these actions and the progression of the AUV. The system is programmed with high-level commands of the style "set depth 3" state1 state2 action 1.1 action 2.1 Figure 1: Simplified Finite State Machine for the AUV. The FSM must be able to fire any type of actions, without knowing anything about them. This problem is addressed by the Command Pattern [GOF95], which encapsulates an action as an object, thereby letting you parameterize clients with different actions. -
Functional Programming Laboratory 1 Programming Paradigms
Intro 1 Functional Programming Laboratory C. Beeri 1 Programming Paradigms A programming paradigm is an approach to programming: what is a program, how are programs designed and written, and how are the goals of programs achieved by their execution. A paradigm is an idea in pure form; it is realized in a language by a set of constructs and by methodologies for using them. Languages sometimes combine several paradigms. The notion of paradigm provides a useful guide to understanding programming languages. The imperative paradigm underlies languages such as Pascal and C. The object-oriented paradigm is embodied in Smalltalk, C++ and Java. These are probably the paradigms known to the students taking this lab. We introduce functional programming by comparing it to them. 1.1 Imperative and object-oriented programming Imperative programming is based on a simple construct: A cell is a container of data, whose contents can be changed. A cell is an abstraction of a memory location. It can store data, such as integers or real numbers, or addresses of other cells. The abstraction hides the size bounds that apply to real memory, as well as the physical address space details. The variables of Pascal and C denote cells. The programming construct that allows to change the contents of a cell is assignment. In the imperative paradigm a program has, at each point of its execution, a state represented by a collection of cells and their contents. This state changes as the program executes; assignment statements change the contents of cells, other statements create and destroy cells. Yet others, such as conditional and loop statements allow the programmer to direct the control flow of the program. -
Framework Overview with UML Diagrams
Framework Overview with UML Diagrams Learn to Build Robust, Scalable and Maintainable Applications using PureMVC Framework Overview This document discusses the classes and interfaces of the PureMVC framework; illustrating their roles, responsibilities and collaborations with simple UML (Unified Modeling Language) diagrams. The PureMVC framework has a very narrow goal. That is to help you separate your application’s coding concerns into three discrete tiers; Model, View and Controller. In this implementation of the classic MVC design meta-pattern, the application tiers are represented by three Singletons (a class where only one instance may be created). A fourth Singleton, the Façade, simplifies development by providing a single interface for communications throughout the application. The Model caches named references to Proxies, which expose an API for manipulating the Data Model (including data retrieved from remote services). The View primarily caches named references to Mediators, which adapt and steward the View Components that make up the user interface. The Controller maintains named mappings to Command classes, which are stateless, and only created when needed. The Façade initializes and caches the Core actors (Model, View and Controller), and provides a single place to access all of their public methods. AUTHOR: Cliff Hall <[email protected]> LAST MODIFIED: 3/05/2008 Façade and Core The Façade class makes it possible for the Proxies, Mediators and Commands that make up most of our final application to talk to each other in a loosely coupled way, without having to import or work directly with the Core framework actors. When we create a concrete Façade implementation for our application, we are able to use the Core actors ‘out of the box’, incidental to our interaction with the Façade, minimizing the amount of API knowledge the developer needs to have to be successful with the framework. -
Co-Occurrence of Design Patterns and Bad Smells in Software Systems
XI Brazilian Symposium on Information System, Goi^ania,GO, May 26-29, 2015. Co-Occurrence of Design Patterns and Bad Smells in Software Systems: An Exploratory Study Bruno Cardoso Eduardo Figueiredo Software Engineering Lab (LabSoft) Software Engineering Lab (LabSoft) Federal University of Minas Gerais (UFMG) Federal University of Minas Gerais (UFMG) Belo Horizonte, MG - Brazil Belo Horizonte, MG - Brazil [email protected] [email protected] ABSTRACT In a previous work [1], we performed a systematic literature A design pattern is a general reusable solution to a recurring review in order to understand how studies investigate these two problem in software design. Bad smells are symptoms that may topics, design patterns and bad smells, together. Our results indicate something wrong in the system design or code. showed that, in general, studies have a narrow view concerning Therefore, design patterns and bad smells represent antagonistic the relation between these concepts. Most of them focus on structures. They are subject of recurring research and typically refactoring opportunities. Among these, some tools [3][7][15][17] appear in software systems. Although design patterns represent have been proposed to identify code fragments that can be good design, their use is often inadequate because their refactored to patterns. Other studies [2][6] establish a structural implementation is not always trivial or they may be unnecessarily relationship between the terms design pattern and bad smell. In employed. The inadequate use of design patterns may lead to a addition, there are reported cases in the literature where the use of bad smell. Therefore, this paper performs an exploratory study in design patterns may not always be the best option and the wrong order to identify instances of co-occurrences of design patterns use of a design pattern can even introduce bad smells in code [19] and bad smells. -
Enterprise Development with Flex
Enterprise Development with Flex Enterprise Development with Flex Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Beijing • Cambridge • Farnham • Köln • Sebastopol • Taipei • Tokyo Enterprise Development with Flex by Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Copyright © 2010 Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky.. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or [email protected]. Editor: Mary E. Treseler Indexer: Ellen Troutman Development Editor: Linda Laflamme Cover Designer: Karen Montgomery Production Editor: Adam Zaremba Interior Designer: David Futato Copyeditor: Nancy Kotary Illustrator: Robert Romano Proofreader: Sada Preisch Printing History: March 2010: First Edition. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Enterprise Development with Flex, the image of red-crested wood-quails, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information con- tained herein.