DOCSLIB.ORG

Introduction to Object-Oriented Programming in MATLAB

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Introduction to Object-Oriented Programming in MATLAB Introduction to Object-Oriented Programming in MATLAB By Stuart McGarrity OBJECT-ORIENTED PROGRAMMING (00) APPLIES TO SOFTWARE DEVELOPMENT the standard science and engineering practice of identifying patterns and de- fining a classification system describing those patterns. Classification systems and design patterns enable engineers and scientists to make sense of complex systems and to reuse efforts by others. By applying classification systems and design patterns to programming, the 00 approach improves your ability to manage software complexity-particularly important when developing and maintaining large applications and data structures. ThiS article demonstrates the use of object-oriented techniques in the MATLAB 16 sensor array with 2 sources language to implement a typical technical o Sensors - - - Direction of Array application. The examples use features avail- -- Direction of Source able in MATLAB 7.6, part of Release 2008a. Application Example: Analyzing Sensor Array Data A sensor array (Figure 1) is a collection of sensors, often arranged in a line, that is used to sample a medium such as air, water, or the ground for radar, sonar, cellular communi- cations, and other applications. By collecting time samples from multiple points in space, you can extract additional information from the medium being sampled. Our application uses a sensor array to determine the direction of arrival (DOA) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 of multiple distant electromagnetic sources, Sensor spacing is 0.125 m such as radio beacons and radar transmit- ters. In this particular scenario, we will FIG URE 1. A sensor array detecting two distant electromagnetic sources at unknown angles. 12 TheMathWorks News&Notes I 2008 The Language of Object- attempt to estimate the angles 91 and 92 of of code, denoted by keywords and end state- the two sources relative to the direction in ments that describe different aspects of the Oriented Programming which the sensor array is pointing. class. The definition file shown in Figure 2 describes a class sads (for sensor array data When creating software applications, the Reviewing Data Items and Operations set), with all the data items that we need to categories you could represent include We will begin by reviewing the data items to represent listed in a properties block. physical objects, such as a car or an or- represent and the operations to implement. ganism; a virtual entity, such as a financial As with most applications, many pieces of Creating an Obiecf and Accessing Properties market; or information, such as a set of data must be stored and tracked to perform To create an object or instance of the class test results. In object-oriented program- the required operations. In our example, we that we defined, we use the statement ming, these categories are represented as need to represent the following data: »s=sads; classes. Data elements, or states, are re- • Numbers of sensors and samples To set the value of a property, we specify its presented as class properties and opera- • Sampled sensor data name just like fields of a structure with tions are implemented as class methods. • Sensor sample rate »s.NumSensors=16; An obiect is an instance of a class- • Sensor spacing We can display the object, seeing all the when a program executes, the object is • Wavelength of distant sources available properties and current values, by created based on its class and behaves • Speed of wave typing its name. in the way defined by the class. The val- • Sensor data set name or description »s ues stored in MATLABvariables all be- We will use a simple FFT-based technique s = long to a closs. These values include not to estimate the DOA of the sources. This sads only what you might normally consider technique can be broken down into parts properties: objects, such as a time series or state and implemented as a collection of opera- NumSensors: 16 space object, but also simple doubles. tions. A small number of utility operations NumSamples: [] needs to be implemented to help with devel- Data: [) opment work. For example, we must: SampleRate: [] identified as a sads object using the class and • Create the data set from synthetic data Spacing: [] isa functions and the whos command, some- or acquired live data Wavelength: [] thing that is not possible with structures. • Inspect and modify data-set values and c: 300000000 » class(s) parameters Name: [] ans = • Plot the sample data to help with inter- list of methods sads pretation and validation All the properties except NumSensors and The ability to identify the class of a vari- • Calculate and plot the averaged magni- c are still empty. The data set can now be able is important to users who create code to tude squared of the FFT (periodogram) of the data set • Find the peaks of the periodogram to es- timate DOA of the sources We can now determine what to represent with class properties and what to implement (just pcoper c re sj with class methods. properties Wavelength % Wavelength o~ sources (m) c""3e8; ~ Speed of wave in medium (m/s) Representing Data NumSensors Number of sensors NwnSamples Number of samples with Class Properties Data Sampled sensor daca We begin by defining a class to describe the Spacing % Spacing of arra7 (m) t4 SampleRate Sample rate (Hz) sensor array. This initial representation con- J. Name % Sensor array test run n~ tains only the data items, representing them 12 end 1-3 end as class properties. You define a class in MATLAB with a class definition file, which contains blocks FIGURE 2. Class definition file sads. mwith properties. TheMathWorks News&Notes I 2008 13 operate on the data set, as it lets them deter- We expand on the class definition file in You then specify a get method that is auto- mine the available data items to be accessed Figure 2 by dividing the current list of prop- matically called when the property is accessed. and operations that can be legally performed. erties into multiple property blocks, each See the "Accessing Properties with Get and Set with unique property attributes: GetAccess, Methods" section of this article for details on Error Checking Constant, and Dependent (Figure 3). how to specify class methods. In our applica- If you use structures to represent your data, You prohibit modification of a property by tion, we set the NumSensors and NumSamples you could add a new field name at any time setting the Constant attribute, In our exam- properties to be dependent. simply by specifying a new field name and ple, we will set the speed of light property c assigning it a value. This capability is partic- to be constant. Because constant properties Implementing Operations with ularly convenient when you are experiment- do not change, they can be accessed simply Class Methods ing with and prototyping algorithms. How- by referencing the class name. Methods, or the operations that can be per- ever, if you misspell a field name, a new field » sads.c _ formed on the object, are specified as a list will be added silently, which might cause an ans ; of functions in a methods block. A class can error later that is difficult to diagnose. 300000000 contain many types of methods, each fulfill- Unlike structures, you cannot arbitrarily add You make a property read-only by setting ing a different purpose, each specified dif- a new property to an object simply by specify- the SetAccess attribute to private. You can ferently. The following section describes a ing a new property name and assigning it a make a property visible only to the meth- number of these types of methods, value. If you misspell an object property name, ods operating on it by setting the GetAccess We will add a methods block to the sads MATLAB immediately issues an error. This ad- attribute to private, as we will do with the definition file and add each new method in- ditional level of error checking is useful when Wavelength property. side this block (Figure 4). the object is being accessed by users who are less You can freely change the names or charac- familiar with it than the author, common during teristics of a private property without affect- Specifying a Constructor Method the development of a large application. ing users of the object. This "black box" ap- In our example, we will specify a constructor proach to defining a piece of software, known method that lets the user provide parameters Controlling Access to Data as encapsulation, prevents the user of the ob- to be used in the creation of the object. The Classes give you great control over property ject from becoming dependent on an imple- constructor method often performs data ini- access. For example, they let you prohibit mentation detail or characteristic that could tialization and validation. The object is now modification of a property, hide a property, change and break their code. created with or cause it to be calculated dynamically. You You specify that a property is calculated »s;sads(Data, wavelength, control access to properties by specifying only when asked for by setting its Dependent SampleRate, Spacing, Name); property attributes in the class definition file. attribute. - c185sc1et sads - c la.!lsdet' sa~ :c seeece Arrav Data Set. elas!! % Sell!!liorArra? Data Set Cla~s propert.ies (Get:A.cce!ls-pr1velCe) arcpecc re e (GeeAccess=privace) [] Wavelengeh \ Wavelength ot eour cee (D'l) properties (Constant.) D end properties (DependenclQ 6 propert.ies (Co~tanel ,. propert.ie~D 1 c-3e8; \ Speed at wave lin medium (ro/!!) j met.hods 8 end tunct.1on obj=sads (Data~ Wavelength,S8l'QpleRate,5pacing~N~) 0 9 properc,1es (Dependene) .function plot (obj) 0 lO NumSensors ~ Number ot sensors funct ion [mags, t.f.lip]-me.gt:t.t (obj, 2eroPadTo) D 1 NUlIIS~ple5 'Number o:f oamples l :function magttcploC,(obj, zeroPadTo) 0 12 end funct.ion angles-doe.
Load more

Recommended publications
  • Operator Overloading ______
    Chapter 10: Operator Overloading _________________________________________________________________________________________________________ Consider the following C++ code snippet: vector<string> myVector(kNumStrings); for(vector<string>::iterator itr = myVector.begin(); itr != myVector.end(); ++itr) *itr += "Now longer!"; Here, we create a vector<string> of a certain size, then iterate over it concatenating “Now longer!” to each of the strings. Code like this is ubiquitous in C++, and initially does not appear all that exciting. However, let's take a closer look at how this code is structured. First, let's look at exactly what operations we're performing on the iterator: vector<string> myVector(kNumStrings); for(vector<string>::iterator itr = myVector.begin(); itr != myVector.end(); ++itr) *itr += "Now longer!"; In this simple piece of code, we're comparing the iterator against myVector.end() using the != operator, incrementing the iterator with the ++ operator, and dereferencing the iterator with the * operator. At a high level, this doesn't seem all that out of the ordinary, since STL iterators are designed to look like regular pointers and these operators are all well-defined on pointers. But the key thing to notice is that STL iterators aren't pointers, they're objects, and !=, *, and ++ aren't normally defined on objects. We can't write code like ++myVector or *myMap = 137, so why can these operations be applied to vector<string>::iterator? Similarly, notice how we're concatenating the string “Now longer!” onto the end of the string: vector<string> myVector(kNumStrings); for(vector<string>::iterator itr = myVector.begin(); itr != myVector.end(); ++itr) *itr += "Now longer!"; Despite the fact that string is an object, somehow C++ “knows” what it means to apply += to strings.
    [Show full text]
  • Property Mapping: a Simple Technique for Mobile Robot Programming
    Property Mapping: a simple technique for mobile robot programming Illah R. Nourbakhsh The Robotics Institute, Carnegie Mellon University Pittsburgh, PA 15213 [email protected] Abstract In this paper we present robot observability as a The mobile robot programming problem is a software predictor for diagnostic transparency. Then, we present a engineering challenge that is not easily conquered using language-independent technique called property mapping contemporary software engineering best practices. We for constructing robot programs that are diagnostically propose robot observability as a measure of the diagnostic transparent and thereby achieve high degrees of transparency of a situated robot program, then describe reliability. property mapping as a simple, language-independent approach to implementing reliable robot programs by maximizing robot observability. Examples from real- The Robot Programming Problem world, working robots are given in Lisp and Java. A mobile robot is a situated automata, or a module that comprises one part of a closed system together with the Introduction environment. Fig. 1 shows the standard depiction of a robot, with its outputs labeled as actions and the outputs The recent availability of inexpensive, reliable robot of the environment in turn labeled as percepts. chassis (e.g. ActivMedia Pioneer, IS-Robotics Magellan, Nomad Scout) has broadened the accessibility of mobile robotics research. Because these robots consist of fixed E hardware out-of-the-box, this technology is shifting the actions A P percepts emphasis of mobile robot research from a joint hardware and software design process toward hardware-unaware R mobile robot programming. This is a software design problem, and yet software Figure 1: The standard view of an embedded robot engineering best practices are not very helpful.
    [Show full text]
  • C++ Properties -- a Library Solution
    Document Number: SC22/WG21/N1615=04-0055 Date: 2004-04-09 Author: Lois Goldthwaite Email: [email protected] C++ Properties -- a Library Solution N1600 is a summary of the "property" language extension that is proposed for C++/CLI. I can't help feeling that this is an effort to impose an alien idiom on C++. There is too much of "the compiler will perform black magic behind your back" in it. There are too many ways in which the programmer must be aware that some [pseudo-]data members must be handled in different ways from [real] data members. The C++/CLI draft spec (N1608)says in 8.8.4 and 18.4 that "A property is a member that behaves as if it were a field." I think "behaves" is absolutely the wrong word to use here. A property is behavior that pretends to be state. From an OO design point of view, I think this is A Bad Idea. Behaviour should be visible; state should not. Further on, the document continues, "the X and Y properties can be read and written as though they were fields. In the example above, the properties are used to implement data hiding within the class itself." The subtle advantage of "hiding" a private data member by treating it as a public data member escapes me. Properties are just syntactic saccharine for getter and setter member functions for individual fields. C++ experts have spent years trying to educate people NOT to use public data, to use member functions instead, and now we propose to introduce something that looks just like public data? Do we really want to try to teach people that public fields are still bad, but properties are good, even though they look just the same from outside the class? Moreover, these public fields have side effects! There is a danger that too many novice programmers will prototype their designs using public fields, with the intent of changing them to properties later, if and when it proves necessary, and the general quality of code will suffer because of it.
    [Show full text]
  • Property Conveyances As a Programming Language
    Property Conveyances as a Programming Language Shrutarshi Basu∗ Nate Foster James Grimmelmann Harvard University Cornell University Cornell Law School & Cornell Tech Cambridge, MA, USA Ithaca, NY, USA New York, NY, USA [email protected] [email protected] [email protected] Abstract 1 Introduction Anglo-American law enables property owners to split up Many legal issues depend on vague, open-ended standards. rights among multiple entities by breaking their ownership For example, nuisance law prohibits “unreasonable” interfer- apart into future interests that may evolve over time. The con- ence with neighbors’ use of land. What counts as “unreason- veyances that owners use to transfer and subdivide property able” depends on an eight-factor balancing test, and many of rights follow rigid syntactic conventions and are governed the individual factors are themselves vague and open-ended, by an intricate body of interlocking doctrines that determine including “the social value that the law attaches to the pri- their legal eect. These doctrines have been codied, but mary purpose of the conduct;” and “the suitability of the only in informal and potentially ambiguous ways. particular use or enjoyment invaded to the character of the This paper presents preliminary work in developing a locality.” [American Law Institute 1979] A lawyer who wants formal model for expressing and analyzing property con- to know whether a client’s cement plant will be considered veyances. We develop a domain-specic language capable a nuisance will have to research numerous previous cases, of expressing a wide range of conveyances in a syntax ap- gather extensive facts about the plant and its neighbors, and proximating natural language.
    [Show full text]
  • Dealing with Properties
    Dealing with Properties Martin Fowler [email protected] lmost every object you create needs properties: some statement about the object. A person may have a height, a company may have a CEO, a flight may have a flight Anumber. There are a number of ways to model properties. In this article I will explore some of these ways and when you may want to use them. I’ve often seen patterns touch on this subject, but they usually only cover part of the picture. Here I want to cover the issue more broadly to give a better discussion of the options. The most common, and the simplest case is to use a Fixed Property, that is just declare the attribute on the class. In the vast majority of cases that is all you need to do. Fixed properties begin to fail when you have a large amount of them, or you need to change them frequently, possibly at run time. These forces lead you to the varieties of Dynamic Property. All dynamic properties have the quality of a parameterized attribute where to query a property you need to use a query method with a parameter. The simplest of these is the Flexible Dynamic Property where the parameter is just a string. This makes it easy to define and use properties, but is difficult to control. If you need that control you can use a Defined Dynamic Property where your parameters must be instances of some class. A further step of control allows you to strongly type your dynamic property with a Typed Dynamic Property.
    [Show full text]
  • Alice Glossary
    Adventures in Alice Programming // Glossary of Useful Terms by Michael Marion // July 2012 Worlds, methods, functions, properties, variables - it’s pretty easy to get all of the terminology and concept matter confused when it comes to programming in Alice. To that point, we’ve developed this handy reference to use. Hopefully it helps you not to get mixed up. Enjoy! World A world in Alice encompasses everything. Just as we’d say that everyone and everything exists in our world in real life; every object, method, event, or anything else lies inside the world in Alice. The whole .a2w file represents the world. Object An object is just what it sounds like. Any sort of three-dimensional shape such as a person, animal, piece of furniture, building, or anything else of the sort in your world is an object. Most objects are added to the world via the Add Objects button, but some - the ground, camera, and light, for instance - are there by default. There are also two-dimensional objects such as text and billboards. Properties An object’s properties are also what they sound like. All objects have certain properties - whether or not they’re showing, their color, their position, and so forth. Color Defines the color of an object. There is a limited number of color choices in Alice, but it covers all primary colors and some extras, including red, blue, green, yellow, black, and cyan. To specify a white object, select “no color”. Opacity Defines the transparency of an object. Unlike isShowing, setting the opacity to a middle amount allows it to be only slightly transparent.
    [Show full text]
  • Operator Overloading in C Sharp with Simple Example
    Operator Overloading In C Sharp With Simple Example Clonic and thick-witted Stephan synopsize his lashkars violated commence laughably. Selig cosponsors his self-understanding refurbishes incompletely, but oculomotor Elias never supernaturalise so earthwards. Morning Robbie never spatted so ineptly or infract any instance detractingly. We will send you exclusive offers when we launch our new service. Even an instance of a class cannot access its private members. Overloading also has surprising ramifications. Net mvc with plus method overloading example overloads must have a simple examples and conceptual way they occur at times. The example with encapsulation comes in. Get in with implicit cast operator methods and examples of overloaded only overload resolution and commentary before. If a variety of ansi sql, if many various other. The example with it in a directional vector class methods in operations of examples of parameters, we avoid building reactive concurrent applications. It adds numbers, concatenates strings or delegates; indicates the sign of a number. In her sense, MATLAB can be used to rapidly prototype an algorithm. Operator specifies an object or two shift operator overloading and b are compiled for this website is only not change these arguments should be accessed from? The process four sections each implement one of different concrete classes. Calling a simple examples of creating an underscore followed if we can be completely new scheduling demands and meaningful. You can definitely overload Casting. This operator with operators, simple examples illustrate, most ad packages based off of operations. We offer such diverse selection of courses from leading universities and cultural institutions from around in world.
    [Show full text]
  • Oberon Script: a Lightweight Compiler and Runtime System for the Web
    Oberon Script: A Lightweight Compiler and Runtime System for the Web Ralph Sommerer1 1 Microsoft Research, 7 J J Thomson Avenue, Cambridge, United Kingdom [email protected] Abstract. Oberon Script is a scripting language and runtime system for build- ing interactive Web Client applications. It is based on the Oberon programming language and consists of a compiler that translates Oberon Script at load-time into JavaScript code, and a small runtime system that detects and compiles script sections written in Oberon Script. 1 Introduction Oberon is the name of a modular, extensible operating system for single user worksta- tions [19], and also of an object-oriented programming language specifically devel- oped to implement the former [17]. Although originally designed as the native operat- ing system for custom built workstations, Oberon was subsequently ported to various different computing platforms including personal computers [2][4] and Unix worksta- tions [1][14][15]. With the recent emergence and proliferation of sophisticated Web client applica- tions, the Web browser has become a computing platform on its own. It offers the Web application programmer scripting facilities to programmatically interact with a Web server, and to manipulate the Web page in-place and without reloading. It thus allows the construction of complex Web application user interfaces that are not lim- ited to the page-based hypertext model anymore. As the Web browser morphs into a runtime system and operating platform for Web client application, the question arises whether it can provide a suitable target platform for one more installment of Oberon, especially in light of all previous porting efforts that have shown Oberon’s demands of the host platform to be very limited.
    [Show full text]
  • Project Oberon the Design of an Operating System and Compiler
    1 Niklaus Wirth Jürg Gutknecht Project Oberon The Design of an Operating System and Compiler Edition 2005 2 Project Oberon Preface This book presents the results of Project Oberon, namely an entire software environment for a modern workstation. The project was undertaken by the authors in the years 1986-89, and its primary goal was to design and implement an entire system from scratch, and to structure it in such a way that it can be described, explained, and understood as a whole. In order to become confronted with all aspects, problems, design decisions and details, the authors not only conceived but also programmed the entire system described in this book, and more. Although there exist numerous books explaining principles and structures of operating systems, there is a lack of descriptions of systems actually implemented and used. We wished not only to give advice on how a system might be built, but to demonstrate how one was built. Program listings therefore play a key role in this text, because they alone contain the ultimate explanations. The choice of a suitable formalism therefore assumed great importance, and we designed the language Oberon as not only an effective vehicle for implementation, but also as a publication medium for algorithms in the spirit in which Algol 60 had been created three decades ago. Because of its structure, the language Oberon is equally well suited to exhibit global, modular structures of programmed systems. In spite of the small number of man-years spent on realizing the Oberon System, and in spite of its compactness letting its description fit a single book, it is not an academic toy, but rather a versatile workstation system that has found many satisfied and even enthusiastic users in academia and industry.
    [Show full text]
  • Object-Oriented Programming in Oberon-2
    Hanspeter Mössenböck Object-Oriented Programming in Oberon-2 Second Edition © Springer‐Verlag Berlin Heidelberg 1993, 1994 This book is out of print and is made available as PDF with the friendly permission of Springer‐Verlag Contents 1 Overview......................................................................................... 1 1.1 Procedure-Oriented Thinking............................................. 1 1.2 Object-Oriented Thinking .................................................... 2 1.3 Object-Oriented Languages................................................. 3 1.4 How OOP Differs from Conventional Programming...... 6 1.5 Classes as Abstraction Mechanisms ................................... 9 1.6 History of Object-Oriented Languages ............................ 11 1.7 Summary .............................................................................. 12 2 Oberon-2........................................................................................ 13 2.1 Features of Oberon-2 .......................................................... 14 2.2 Declarations ......................................................................... 14 2.3 Expressions .......................................................................... 16 2.4 Statements ............................................................................ 18 2.5 Procedures............................................................................ 19 2.6 Modules................................................................................ 21 2.7 Commands..........................................................................
    [Show full text]
  • Discovering Hidden Properties to Attack Node.Js Ecosystem
    Discovering Hidden Properties to Attack Node.js Ecosystem Feng Xiao, Jianwei Huang, Yichang Xiong, Guangliang Yang, Hong Hu, Guofei Gu, Wenke Lee #BHUSA @BLACKHATEVENTS Feng Xiao @f3ixiao • CS PhD student at Georgia Tech. • Vulnerability researcher. Develop tools to detect and exploit 0days. • Focus on web/application security, but also enjoy network security+ and virtualization security. +Hacking the Brain: Customize Evil Protocol to Pwn an SDN Controller. DEF CON 2018 #BHUSA @BLACKHATEVENTS Agenda • Hi, you’ve found some new Node.js vulnerabilities! what are they? • Sounds interesting, you’ve built bug finding tools? how does it work? • Cool. More details on the real-world impact? #BHUSA @BLACKHATEVENTS $ cat vuls.txt #BHUSA @BLACKHATEVENTS Background $ man node • A JavaScript runtime built on Chrome’s v8 engine. Apps AppApps Code Core Modules libuv … Node.js Operating System #BHUSA @BLACKHATEVENTS $ man node • A JavaScript runtime built on Chrome’s v8 engine. • Widely-used for deploying server-side programs and desktop apps. #BHUSA @BLACKHATEVENTS $ man node • A JavaScript runtime built on Chrome’s v8 engine. • Widely-used for deploying server-side programs and desktop apps. • Object sharing is a very popular communication method for Node.js web apps. Request parsing modules that convert input into objects. #BHUSA @BLACKHATEVENTS Object Sharing GET /update?age=23 Querystring-based Serialization Client-side JS {func: update, age: 23} JSON-based Serialization Node.js web #BHUSA @BLACKHATEVENTS What if we inject additional properties that are unexpected to the program? Hidden Property Abusing HPA leverages the widely-used data exchanging feature in Node.js (object sharing) to tamper or forge critical program states of Node.js applications.
    [Show full text]
  • A GROOVY Way to Enhance Your SAS Life
    Paper CT05 A GROOVY way to enhance your SAS life Karl Kennedy, GCE Solutions, Manchester, UK ABSTRACT PROC GROOVY is a relatively new (SAS® 9.3+) and little-known SAS procedure that can unleash the power of Apache's GROOVY language (Java™-syntax compatible object-oriented programming language) within your SAS environment. To display the power of PROC GROOVY two methods for producing a bookmarked PDF containing trial results (tables, figures, and listings) are described. The first method uses PROC GROOVY/Java while the second uses standard BASE SAS. The primary goal of this paper is to show that with minimal Java and PROC GROOVY knowledge the programming burden/complexity of the task can be greatly reduced, for example by removing the requirement to parse an RTF file. This is achieved by utilising Java's vast collection of Application Programming Interfaces (APIs). A secondary goal is to open the world of Java to SAS programmers. INTRODUCTION In Clinical Trial reporting it is often required to provide the analysis results (tables, figures, and listings (TFLs)) in one complete PDF document. In a previous role, a client made such a request at the end of the study and without any process in place to handle this request we had to investigate how to combine all the RTFs into one PDF document. Fortunately, an excellent paper “A SAS Macro Utility to Append SAS-Generated RTF Outputs and Create the Table of Contents” [1] describes how to append RTF tables and listings into one RTF document which could then be saved as a PDF file.
    [Show full text]