Smalltalk Tutorial for Java Programmers!
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Traits: Experience with a Language Feature
7UDLWV([SHULHQFHZLWKD/DQJXDJH)HDWXUH (PHUVRQ50XUSK\+LOO $QGUHZ3%ODFN 7KH(YHUJUHHQ6WDWH&ROOHJH 2*,6FKRRORI6FLHQFH1(QJLQHHULQJ$ (YHUJUHHQ3DUNZD\1: 2UHJRQ+HDOWKDQG6FLHQFH8QLYHUVLW\ 2O\PSLD$:$ 1::DONHU5G PXUHPH#HYHUJUHHQHGX %HDYHUWRQ$25 EODFN#FVHRJLHGX ABSTRACT the desired semantics of that method changes, or if a bug is This paper reports our experiences using traits, collections of found, the programmer must track down and fix every copy. By pure methods designed to promote reuse and understandability reusing a method, behavior can be defined and maintained in in object-oriented programs. Traits had previously been used to one place. refactor the Smalltalk collection hierarchy, but only by the crea- tors of traits themselves. This experience report represents the In object-oriented programming, inheritance is the normal way first independent test of these language features. Murphy-Hill of reusing methods—classes inherit methods from other classes. implemented a substantial multi-class data structure called ropes Single inheritance is the most basic and most widespread type of that makes significant use of traits. We found that traits im- inheritance. It allows methods to be shared among classes in an proved understandability and reduced the number of methods elegant and efficient way, but does not always allow for maxi- that needed to be written by 46%. mum reuse. Consider a small example. In Squeak [7], a dialect of Smalltalk, Categories and Subject Descriptors the class &ROOHFWLRQ is the superclass of all the classes that $UUD\ +HDS D.2.3 [Programming Languages]: Coding Tools and Tech- implement collection data structures, including , , 6HW niques - object-oriented programming and . The property of being empty is common to many ob- jects—it simply requires that the object have a size method, and D.3.3 [Programming Languages]: Language Constructs and that the method returns zero. -
C++ Programming: Program Design Including Data Structures, Fifth Edition
C++ Programming: From Problem Analysis to Program Design, Fifth Edition Chapter 5: Control Structures II (Repetition) Objectives In this chapter, you will: • Learn about repetition (looping) control structures • Explore how to construct and use count- controlled, sentinel-controlled, flag- controlled, and EOF-controlled repetition structures • Examine break and continue statements • Discover how to form and use nested control structures C++ Programming: From Problem Analysis to Program Design, Fifth Edition 2 Objectives (cont'd.) • Learn how to avoid bugs by avoiding patches • Learn how to debug loops C++ Programming: From Problem Analysis to Program Design, Fifth Edition 3 Why Is Repetition Needed? • Repetition allows you to efficiently use variables • Can input, add, and average multiple numbers using a limited number of variables • For example, to add five numbers: – Declare a variable for each number, input the numbers and add the variables together – Create a loop that reads a number into a variable and adds it to a variable that contains the sum of the numbers C++ Programming: From Problem Analysis to Program Design, Fifth Edition 4 while Looping (Repetition) Structure • The general form of the while statement is: while is a reserved word • Statement can be simple or compound • Expression acts as a decision maker and is usually a logical expression • Statement is called the body of the loop • The parentheses are part of the syntax C++ Programming: From Problem Analysis to Program Design, Fifth Edition 5 while Looping (Repetition) -
7. Control Flow First?
Copyright (C) R.A. van Engelen, FSU Department of Computer Science, 2000-2004 Ordering Program Execution: What is Done 7. Control Flow First? Overview Categories for specifying ordering in programming languages: Expressions 1. Sequencing: the execution of statements and evaluation of Evaluation order expressions is usually in the order in which they appear in a Assignments program text Structured and unstructured flow constructs 2. Selection (or alternation): a run-time condition determines the Goto's choice among two or more statements or expressions Sequencing 3. Iteration: a statement is repeated a number of times or until a Selection run-time condition is met Iteration and iterators 4. Procedural abstraction: subroutines encapsulate collections of Recursion statements and subroutine calls can be treated as single Nondeterminacy statements 5. Recursion: subroutines which call themselves directly or indirectly to solve a problem, where the problem is typically defined in terms of simpler versions of itself 6. Concurrency: two or more program fragments executed in parallel, either on separate processors or interleaved on a single processor Note: Study Chapter 6 of the textbook except Section 7. Nondeterminacy: the execution order among alternative 6.6.2. constructs is deliberately left unspecified, indicating that any alternative will lead to a correct result Expression Syntax Expression Evaluation Ordering: Precedence An expression consists of and Associativity An atomic object, e.g. number or variable The use of infix, prefix, and postfix notation leads to ambiguity An operator applied to a collection of operands (or as to what is an operand of what arguments) which are expressions Fortran example: a+b*c**d**e/f Common syntactic forms for operators: The choice among alternative evaluation orders depends on Function call notation, e.g. -
The Future: the Story of Squeak, a Practical Smalltalk Written in Itself
Back to the future: the story of Squeak, a practical Smalltalk written in itself Dan Ingalls, Ted Kaehler, John Maloney, Scott Wallace, and Alan Kay [Also published in OOPSLA ’97: Proc. of the 12th ACM SIGPLAN Conference on Object-oriented Programming, 1997, pp. 318-326.] VPRI Technical Report TR-1997-001 Viewpoints Research Institute, 1209 Grand Central Avenue, Glendale, CA 91201 t: (818) 332-3001 f: (818) 244-9761 Back to the Future The Story of Squeak, A Practical Smalltalk Written in Itself by Dan Ingalls Ted Kaehler John Maloney Scott Wallace Alan Kay at Apple Computer while doing this work, now at Walt Disney Imagineering 1401 Flower Street P.O. Box 25020 Glendale, CA 91221 [email protected] Abstract Squeak is an open, highly-portable Smalltalk implementation whose virtual machine is written entirely in Smalltalk, making it easy to debug, analyze, and change. To achieve practical performance, a translator produces an equivalent C program whose performance is comparable to commercial Smalltalks. Other noteworthy aspects of Squeak include: a compact object format that typically requires only a single word of overhead per object; a simple yet efficient incremental garbage collector for 32-bit direct pointers; efficient bulk- mutation of objects; extensions of BitBlt to handle color of any depth and anti-aliased image rotation and scaling; and real-time sound and music synthesis written entirely in Smalltalk. Overview Squeak is a modern implementation of Smalltalk-80 that is available for free via the Internet, at http://www.research.apple.com/research/proj/learning_concepts/squeak/ and other sites. It includes platform-independent support for color, sound, and image processing. -
While Statement in C
While Statement In C EnricoIs Reg alwaysdisheartening deplete or his novel aspects when chagrined luminesced disputatiously, some crayfishes he orbits clump so temporizingly? grindingly. Solid Ring-necked and comose Bennet Brendan tarnishes never tensehalf-and-half his Stuttgart! while Thank you use a counter is a while loop obscures the condition which is evaluated to embed videos in while c program C while loops statement allows to repeatedly run at same recipient of code until a wrap is met while loop is empty most basic loop in C programming while loop. We then hand this variable c in the statement block and represent your value for each. While adultery in C Set of instructions given coil the compiler to night set of statements until condition becomes false is called loops. If it is negative number added to the condition in c language including but in looping structures, but is executed infinite loop! While Loop Definition Example & Results Video & Lesson. While talking in C Know Program. What is the while eternal in C? A while loop around loop continuously and infinitely until the policy inside the parenthesis becomes false money must guard the. C while and dowhile Loop Programiz. Programming While Loop. The widow while redeem in the C language is basically a post tested loop upon the execution of several parts of the statements can be repeated by reckless use children do-while. 43 Loops Applications in C for Engineering Technology. Do it Loop in C Programming with Examples Phptpoint. Statements and display control C Tutorials Cpluspluscom. Do while just in c example program. -
Type Feedback for Bytecode Interpreters Position Paper ICOOOLPS 2007
Type Feedback for Bytecode Interpreters Position Paper ICOOOLPS 2007 Michael Haupt1, Robert Hirschfeld1, and Marcus Denker2 1 Software Architecture Group Hasso-Plattner-Institut University of Potsdam, Germany 2 Software Composition Group Institute of Computer Science and Applied Mathematics University of Berne, Switzerland michael.haupt,hirschfeld @hpi.uni-potsdam.de, [email protected] { } Abstract. This position paper proposes the exploitation of type feed- back mechanisms, or more precisely, polymorphic inline caches, for purely interpreting implementations of object-oriented programming languages. Using Squeak’s virtual machine as an example, polymorphic inline caches are discussed as an alternative to global caching. An implementation proposal for polymorphic inline caches in the Squeak virtual machine is presented, and possible future applications for online optimization are outlined. 1 Introduction Bytecode interpreters are small in size and comparatively easy to implement, but generally execute programs much less efficiently than just-in-time (JIT) compilers. Techniques like threaded interpretation [9, 11, 2] focus on speeding up bytecode interpretation itself, and caching [4, 5, 1] improves the performance of message sends—the most common operation in object-oriented software [7]. It is interesting to observe that, while threading mechanisms are used natu- rally to a varying degree in bytecode interpreter implementations, such systems usually employ only global caching to speed up dynamic method dispatch. A global cache is clearly beneficial with respect to overall performance. Still, it does not provide optimal support for polymorphic message send sites, and it does not allow for exploiting type information (we provide details on these issues in the following section). In our opinion, the employment of polymorphic inline caches (PICs) [5] instead can provide means for achieving significant speedups in bytecode interpreters while exhibiting only a moderate increase in memory footprint and implementation complexity. -
Graphical Interface
Appendix: How to program in Croquet Author: S.M. Wolff Project: Cell-Forum Project Table of Contents Table of Contents .............................................................................................................. 2 Graphical Interface ........................................................................................................... 6 Control structures .............................................................................................................. 9 Testing variables ............................................................................................................... 9 If then else ........................................................................................................................ 10 Switch ............................................................................................................................ 10 While .............................................................................................................................. 10 For .................................................................................................................................. 11 Data structures ............................................................................................................ 12 Ordered Collection ...................................................................................................... 12 Classes, Methods and Shared Variables .................................................................... 13 Packages ..................................................................................................................... -
Chapter 6 Flow of Control
Chapter 6 Flow of Control 6.1 INTRODUCTION “Don't you hate code that's In Figure 6.1, we see a bus carrying the children to not properly indented? school. There is only one way to reach the school. The Making it [indenting] part of driver has no choice, but to follow the road one milestone the syntax guarantees that all after another to reach the school. We learnt in Chapter code is properly indented.” 5 that this is the concept of sequence, where Python executes one statement after another from beginning to – G. van Rossum the end of the program. These are the kind of programs we have been writing till now. In this chapter Figure 6.1: Bus carrying students to school » Introduction to Flow of Control Let us consider a program 6-1 that executes in » Selection sequence, that is, statements are executed in an order in which they are written. » Indentation The order of execution of the statements in a program » Repetition is known as flow of control. The flow of control can be » Break and Continue implemented using control structures. Python supports Statements two types of control structures—selection and repetition. » Nested Loops 2021-22 Ch 6.indd 121 08-Apr-19 12:37:51 PM 122 COMPUTER SCIENCE – CLASS XI Program 6-1 Program to print the difference of two numbers. #Program 6-1 #Program to print the difference of two input numbers num1 = int(input("Enter first number: ")) num2 = int(input("Enter second number: ")) diff = num1 - num2 print("The difference of",num1,"and",num2,"is",diff) Output: Enter first number 5 Enter second number 7 The difference of 5 and 7 is -2 6.2 SELECTION Now suppose we have `10 to buy a pen. -
While and Do-While Loops
While and Do-While Loops 15-110 Summer 2010 Margaret Reid-Miller Loops • Within a method, we can alter the flow of control using either conditionals or loops. • The loop statements while, do-while, and for allow us execute a statement(s) over and over. • Like a conditional, a loop is controlled by a boolean expression that determines how many times the statement is executed. E.g., You may want to calculate the interest paid on a mortgage for each year of the loan term. Summer 2010 15-110 (Reid-Miller) The while statement • The form of the while statement is while (<boolean_expression>) <statement> • If boolean_expression evaluates to true, then statement is executed. • Then, the boolean_expression is evaluated again. If it evaluates to true, statement is executed again. • This repetition continues until the boolean_expression evaluates to false. How is the while loop different from the if statement? Summer 2010 15-110 (Reid-Miller) The if Flowchart false boolean_expression true statement (body of loop) Summer 2010 15-110 (Reid-Miller) The while Flowchart false boolean_expression true statement (body of loop) Summer 2010 15-110 (Reid-Miller) A Example n = 5 while i output 0 Print n asterisks! i < n ? *! 1 int i = 0; ! i < n ? while (i < n) { ! ! **! System.out.print(“*”);! 2 i < n ? !i++;! ***! }! 3 i < n ? System.out.println();! ****! 4 i < n ? *****! 5 i < n ? ***** Summer 2010 15-110 (Reid-Miller) The Loop Control Variable • The variable i (known as the loop control variable) is used in three ways: it is initialized, tested, and updated.! -
2008 Chevrolet Cobalt Owner Manual M
2008 Chevrolet Cobalt Owner Manual M Seats and Restraint Systems ........................... 1-1 Driving Your Vehicle ....................................... 4-1 Front Seats ............................................... 1-2 Your Driving, the Road, and Your Vehicle ..... 4-2 Rear Seats ............................................... 1-9 Towing ................................................... 4-32 Safety Belts ............................................. 1-10 Service and Appearance Care .......................... 5-1 Child Restraints ....................................... 1-30 Service ..................................................... 5-3 Airbag System ......................................... 1-53 Fuel ......................................................... 5-5 Restraint System Check ............................ 1-68 Checking Things Under the Hood ............... 5-10 Features and Controls ..................................... 2-1 Headlamp Aiming ..................................... 5-39 Keys ........................................................ 2-3 Bulb Replacement .................................... 5-42 Doors and Locks ...................................... 2-10 Windshield Wiper Blade Replacement ......... 5-48 Windows ................................................. 2-15 Tires ...................................................... 5-49 Theft-Deterrent Systems ............................ 2-18 Appearance Care ..................................... 5-95 Starting and Operating Your Vehicle ........... 2-21 Vehicle Identification -
MVC Revival on the Web
MVC Revival on the Web Janko Mivšek [email protected] @mivsek @aidaweb ESUG 2013 Motivation 30 years of Smalltalk, 30 years of MVC 34 years exa!tly, sin!e "#$# %ot in JavaScri&t MVC frameworks 'or Sin(le)*age and +ealtime web a&&s ,e Smalltalkers s-ould respe!t and revive our &earls better Contents MVC e &lained %istory /sa(e in !.rrent JavaScri&t frameworks /sa(e in Smalltalk C.rrent and f.t.re MVC in 0ida/Web MVC Explained events Ar!hite!tural desi(n &attern - Model for domain s&e!ifi! data and logi! View updates Controller ) View for &resentation to t-e .ser ) Controller for intera!tions wit- t-e .ser UI and .&datin( domain model Domain changes Main benefit: actions observing ) se&aration of !on!erns Model MVC based on Observer pattern subscribe ) 3bserver looks at observee Observer changed - 3bservee is not aware of t-at s u 4e&enden!y me!-anism2 B t n - 3bserver is de&endent on 3bservee state e observing v - 3bservee m.st re&ort state !-an(es to 3bserver E b - *.b/S.b Event 6.s de!ou&les 3bservee from u S / 3bserver to &reserve its .nawarnes of observation b u changed P Observee Main benefit: (Observable) ) se&aration of !on!erns Multiple observers subscribe - M.lti&le observers of t-e same 3bservee Observer changed - 7n MVC an 3bservee is View and 3bservee is domain Model, t-erefore2 s u B t - many views of t-e same model n e observing v - many a&&s E b - many .sers u S / - mix of all t-ree !ases b u Observee changed P (Observable) Example: Counter demo in Aida/Web M.lti.ser realtime web !ounter exam&le -ttp://demo.aidaweb.si – !li!k Realtime on t-e left – !li!k De!rease or In!rease to c-an(e counter – !ounter is c-an(ed on all ot-er8s browsers History of MVC (1) 7nvented by 9rygve +eenska.g w-en -e worked in "#$:1$# wit- Alan ;ay's group on <ero *arc on Smalltalk and Dynabook – 'inal term Model)View)Controller !oined 10. -
Chapter 5: Conditionals and Loops Lab Exercises
Chapter 5: Conditionals and Loops Lab Exercises Topics Lab Exercises Boolean expressions PreLab Exercises The if statement Computing a Raise The switch statement A Charge Account Statement Activities at Lake LazyDays Rock, Paper, Scissors Date Validation Conditional Operator Processing Grades The while statement PreLab Exercises Counting and Looping Powers of 2 Factorials A Guessing Game Iterators & Reading Text Files Baseball Statistics The do statement More Guessing Election Day The for statement Finding Maximum and Minimum Values Counting Characters Using the Coin Class Drawing with loops and conditionals A Rainbow Program Determining Event Sources Vote Counter, Revisited Dialog Boxes Modifying EvenOdd.java A Pay Check Program Checkboxes & Radio Buttons Adding Buttons to StyleOptions.java Chapter 5: Conditionals and Loops 65 Prelab Exercises Sections 5.1-5.3 1. Rewrite each condition below in valid Java syntax (give a boolean expression): a. x > y > z b. x and y are both less than 0 c. neither x nor y is less than 0 d. x is equal to y but not equal to z 2. Suppose gpa is a variable containing the grade point average of a student. Suppose the goal of a program is to let a student know if he/she made the Dean's list (the gpa must be 3.5 or above). Write an if... else... statement that prints out the appropriate message (either "Congratulations—you made the Dean's List" or "Sorry you didn't make the Dean's List"). 3. Complete the following program to determine the raise and new salary for an employee by adding if ..