Run For Leprosy!

Hallo teman-teman!

Pada tanggal 15 Maret 2015 kemarin, TFI Binus mengadakan kegiatan Run For Leprosy dengan bekerja sama bersama pihak Alam Sutra.Bagi yang belum tau TFI, TEACH FOR INDONESIA (TFI) adalah Community Program yang concern terhadap aspek pembelajaran dengan konsep pembinaan komunitas yang bertujuan agar komunitas tersebut dapat mandiri dan dapat meningkatkan kualitas hidup komunitas tersebut khususnya bagi perkembagan masa depan anak-anak. Singkat cerita, TFI adalah komunitas mahasiswa Binus yang peduli terhadap perkembangan masa depan anak-anak Indonesia.

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Pada kesempatan kali ini, TFI mengambil topik Leprosy (penyakit Kusta). Penyakit kusta atau lepra (leprosy) atau disebut juga Morbus Hansen, adalah sebuah penyakit infeksi menular kronis yang disebabkan oleh bakteri Mycobacterium leprae.

Apa itu Leprosy / Kusta?

Penyakit kusta disebabkan oleh kuman yang dimakan sebagai microbakterium, dimana microbacterium ini adalah kuman aerob, tidak membentuk spora, berbentuk batang yang tidak mudah diwarnai namun jika diwarnai akan tahan terhadap dekolorisasi oleh asam atau alkohol sehingga oleh karena itu dinamakan sebagai basil “tahan asam”.

Mekanisme penularan yang tepat belum diketahui. Beberapa hipotesis telah dikemukakan seperti adanya kontak dekat dan penularan dari udara. Dan diduga faktor genetika juga ikut berperan, setelah melalui penelitian dan pengamatan pada kelompok penyakit kusta di keluarga tertentu. Belum diketahui pula mengapa dapat terjadi tipe kusta yang berbeda pada setiap individu. (dikutip dari http://www.indosiar.com/ragam/apa-dan-bagaimana-penyakit-kusta_79313.html).

Sosialisasi di Indonesia mengenai penyakit ini sangatlah kurang, karena itu hanya sedikit sekali masyarakat Indonesia yang concern dan mengetahui tentang komunitas kusta di Indonesia.

Kesan dan Pesan terhadap acara Run For Leprosy

TFI mencoba mengangkat tema Leprosy dan mengemas acara berupa sebuah acara marathon sejauh 5 atau 10 kilometer yang berlokasi di daerah alam sutra. Acara marathon saat ini sangatlah fenomenal di kalangan masyarakat, oleh karena itu kreativitas TFI patutlah diacungi jempol karena dapat mengemas topik Leprosy ke dalam acara ini.

Ketika kita mengikuti acara ini, kita diberikan baju Run For Leprosy yang bermotifkan polkadot. Dengan mengikuti kegiatan ini, kita diajak untuk mulai mengerti dan menerima teman-teman yang terkena atau pernah terkena kusta. Semangat dari setiap pelari yang terus berjuang sampai ke garis finish menjadi salah satu inspirasi untuk mengadakan sebuah acara charity untuk rekan-rekan yang saat ini sedang terkena atau sudah sembuh dari kusta.

Kesan saya terhadap acara ini adalah acara ini sangatlah kreatif dan ada baiknya acara semacam ini diadakan oleh pihak-pihak penyelenggara lainnya di luar sana. Pesan saya terhadap acara ini adalah akan lebih baik apabila diadakan booth kreatifitas seperti mini games, dan lain sebagainya.

Komitmen Dari Diri

Melalui kegiatan ini, saya dapat mengambil komitmen untuk tidak membeda-bedakan komunitas kusta dengan orang-orang biasa, karena seperti kita, mereka adalah saudara kita yang membutuhkan bantuan kita ketika mereka kesulitan. Karena itu daripada menjauhi mereka, lebih baik kita ulurkan tangan kita untuk membantu mereka.

Saran Bagaimana Sosialisasi Yang Baik

Saran saya dalam sosialisasi penyakit Leprosy ini adalah ada baiknya diadakan kegiatan-kegiatan semacam ini lagi. Karena dengan kegiatan yang melibatkan banyak orang dan kreatifitas, kita dapat lebih mengetahui dan peduli terhadap issue sosial seperti Leprosy.

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Programming Language Concept – Chapter 16

1. What are the three primary uses of symbolic logic in formal logic?

• to express propositions

• to express the relationships between propositions, and

• to describe how new propositions can be inferred from other propositions that are assumed to be true.

2. Two parts of a compound term are: a functor, which is the function symbol that names the relation, and an ordered list of parameters, which together represent an element of the relation.

3. Propositions can be stated in two modes: one in which the proposition is defined to be true, and one in which the truth of the proposition is something that is to be determined. In other words, propositions can be stated to be facts or queries.

5. Antecedents are the right side of clausal form propositions, whereas Consequents are the left side of clausal form propositions, because it is the consequence of the truth of the antecedent.

7. What are the forms of Horn clauses ?
• Have a single atomic proposition on the left side
• empty left side.

9. What does it mean for a language to be nonprocedural ?
– Language in which the programs do not exactly state how a result is to be computed but rather describe the form of the result.

11. An uninstantiated variable is a variable that has not been assigned a value.

13. Conjunctions contain multiple terms that are separated by logical AND operations.

PROBLEM SET

1.”All predicate calculus propositions can be algorithmically converted to clausal form”. Is this statement true or false?

This statement is true. Nilsson (1971) gives proof that this can be done, as well as a simple conversion algorithm for doing it.

2. Describe how a logic programming language is different from a general programming language.

Programming that uses a form of symbolic logic as a programming language, unlike other general programming language, is often called logic programming; languages based on symbolic logic are called logic programming languages, or declarative languages.

7. Horn clauses can be in only two forms: They have either a single atomic proposition on the left side or an empty left side. The left side of a clausal form proposition is sometimes called the head, and Horn clauses with left sides are called headed Horn clauses. Headed Horn clauses are used to state relationships, such as

likes( bob, trout ) likes( bob, fish ) x fish( trout )

8. Critically comment on the following statement : “ Logic programs are nonprocedural”
– It is true, because logical programs use lots of different processes based on its conditions. If a certain logical requirement is true, then a program will execute the corresponding process, instead of procedurally executing the statements.

10. Using the internet for reference, find some of the applications of expert systems.

• Expert system in healthcare: The Electronic health record (EHR) is designed to replace the traditional medical and bring together a more versatile, expansive and robust expert system to provide greater quality care.

• Expert systems in the financial field: Loan departments are interested in expert systems for morgages because of the growing cost of labour, which makes the handling and acceptance of relatively small loans less profitable.

• A new application for expert systems is automated computer program generation. Funded by a US Air Force grant, an expert system-based application (hprcARCHITECT) that generates computer programs for mixed processor technology (FPGA/GPU/Multicore) systems without a need for technical specialists has recently been commercially introduced

Programming Language Concept – Chapter 15

2. A lambda expression specifies the parameters and the mapping of a function.

3. Atoms and lists were parts of the original LISP.

6. Simple list is a list which membership of a given atom in a given list that does not include sublists.

7. REPL stand for read-evaluate-print loop.

8. Three parameters to IF are: a predicate expression, a then expression, and an else expression.

18. A function is tail recursive if its recursive call is the last operation in the function. This means that the return value of the recursive call is the return value of the nonrecursive call to the function. It is important to specify repetition to be tail recursive because it is more efficient(increase the efficiency).

22. During reader phase of a common LISP language processor, There is a special kind of macro, named reader macros or read macros, that are expanded. A reader macro expands a specific character into a string of LISP code. For example, the apostrophe in LISP is a read macro that expands to a call to QUOTE.

24. What is stored in an ML evaluation environment?

A table called the evaluation environment stores the names of all implicitly and explicitly declared identifiers in a program, along with their types. This is like a run-time symbol table.

29. Curried function let new functions can be constructed from them by partial evaluation.

30. Partial evaluation means that the function is evaluated with actual parameters for one or more of the leftmost formal parameters.

33. Explain the process of currying.
The process of currying replaces a function with more than one parameter with a function with one parameter that returns a function that takes the other parameters of the initial function.

35. A language is nonstrict if it does not have the strict requirement.

43. What is the syntax of a lambda expression in F#?

The following lambda expression illustrates their syntax:
(fun a b −> a / b)

PROBLEM SET

2. Give the general form of function declaration in ML.

Function declarations in ML appear in the general form
fun function_name( formal parameters ) = expression;

8. How is the functional operator pipeline ( | > )used in F#?

The pipeline operator is a binary operator that sends the value of its left operand, which is an expression, to the last parameter of the function call, which is the right operand. It is used to chain together function calls while flowing the data being processed to each call.

Consider the following example code, which uses the high-order functions filter and map:

let myNums = [1; 2; 3; 4; 5]
let evensTimesFive = myNums

|> List.filter (fun n −> n % 2 = 0)

10. What does the following Scheme function do?

(define ( x lis)

(cond

(( null? lis) 0 )

(( not(list? (car lis)))

(cond

((eq? (car lis) #f) (x (cdr lis)))

(else (+1 (x (cdr lis))))))

(else (+ (x (car lis)) (x (cdr lis))))

x returns the number of non-#f atoms in the given list

|> List.map (fun n −> 5 * n)

Programming Language Concept – Chapter 14

6 . What is exception propagation in Ada?

Exception propagation allows an exception raised in one program unit to be handled in some other unit in its dynamic or static ancestry. This allows a single exception handler to be used for any number of different program units. This reuse can result in significant savings in development cost, program size, and program complexity.

9. What is the scope of exception handlers in Ada?

Exception handlers can be included in blocks or in the bodies of subprograms, packages, or tasks.

10. What are the four exceptions defined in the Standard package of Ada?

There are four exceptions that are defined in the default package, Standard:

Constraint_aError

Program_Error

Storage_Error

Tasking_Error

11. are they any predefined exceptions in Ada?

Yes, they are.

12. What is the use of Suppress pragma in Ada?

The suppress pragma is used to disable certain run-time checks that

are parts of the built-in exceptions in Ada.

14. What is the name of all C++ exception handlers?

Try clause.

30. In which version were assertions added to Java?

Assertions were added to Java in version 1.4.

31. What is the use of the assert statement?

The assert statement is used for defensive programming. A program may be written with many assert statements, which ensure that the program’s computation is on track to produce correct results.

32. What is event-driven programming?

Event-driven programming is a programming where parts of the program are executed at completely unpredictable times, often triggered by user interactions with the executing program.

33. What is the purpose of a Java JFrame?

The JFrame class defines the data and methods that are needed for frames. So, a class that uses a frame can be a subclass of JFrame. A JFrame has several layers, called panes.

34. What are the different forms of assert statement?

There are two possible forms of the assert statement:

assert condition;

assert condition : expression;

PROBLEM SET:

1.What mechanism did early programming languages provide to detect or attempt to deal with errors?

Early programming languages were designed and implemented in such a way that the user program could neither detect nor attempt to deal with such errors. In these languages, the occurrence of such an error simply causes the program to be terminated and control to be transferred to the operating system.

2.Describe the approach for the detection of subscript range errors used in C and Java.

In C subscript ranges are not checked. Java compilers usually generate code to check the correctness of every subscript expression. If any exception generates, then an unchecked exception is thrown.

6.In languages without exception-handling facilities, it is common to have most subprograms include an “error” parameter, which can be set to some values representing “OK” or some other value representing “error in procedure”. What advantage does a linguistic exception-handling facility like that of Ada have over this method?

There are several advantages of a linguistic mechanism for handling exceptions, such as that found in Ada, over simply using a flag error parameter in all subprograms. One advantage is that the code to test the flag after every call is eliminated. Such testing makes programs longer and harder to read. Another advantage is that exceptions can be propagated farther than one level of control in a uniform and implicit way. Finally, there is the advantage that all programs use a uniform method for dealing with unusual circumstances, leading to enhanced readability.

7.In languages without exception-handling facilities, we could send an error-handling procedure as parameter to each procedure that can detect errors than must be handled. What disadvantage are there to this method?

There are several disadvantages of sending error handling subprograms to other subprograms. One is that it may be necessary to send several error handlers to some subprograms, greatly complicating both the writing and execution of calls. Another is that there is no method of propagating exceptions, meaning that they must all be handled locally. This complicates exception handling, because it requires more attention to handling in more places.

14. Summarize the arguments in favor of the termination and resumption models of continuation.

The resumption model is useful when the exception is only an unusual condition, rather than an error. The termination model is useful when the exception is an error and it is highly unlikely that the error can be corrected so that execution could continue in some useful way.

Programming Language Concept – Chapter 13

Review Question

1. Three possible levels of concurrency in programs:
• instruction level (executing two or more machine instructions simultaneously),
• statement level (executing two or more high-level language statements simultaneously)
• unit level (executing two or more subprogram units simultaneously)

2. In an SIMD computer, each processor has its own local memory. One processor controls the operation of the other processors. Because all of the processors, except the controller, execute the same instruction at the same time, no synchronization is required in the software.

5. Unit-level concurrency is best supported by MIMD computers.

6. Vector processor have groups of registers that store the operands of a vector operation in which
the same instruction is executed on the whole group of operands simultaneously.

7. Physical concurrency is several program units from the same program that literally execute simultaneously.

Logical concurrency is multiple processors providing actual concurrency, when in fact the actual execution of programs is taking place in interleaved fashion on a single processor.

8. A scheduler manages the sharing of processors among the tasks. If there were never any interruptions and tasks all had the same priority, the scheduler could simply give each task a time slice, such as 0.1 second, and when a task’s turn came, the scheduler could let it execute on a processor for that amount of time.

16. A task descriptor is a data structure that stores all of the relevant information about the execution state of a task.

18. The purpose of a task-ready queue is to be storage of tasks that are ready to run.

21. A binary semaphore is a semaphore that requires only a binary-valued counter.

A counting semaphore is a synchronization object that can have an arbitrarily large number of states.

30. Ada terminate clause, when selected, means that the task is finished with its job but is not yet terminated. Task termination is discussed later in this section.

34. Sleep method in Java blocks the the thread.

35. Yield method in Java surrenders the processor voluntarily as a request from the running thread.

36. The join method in Java is used to force a method to delay its execution until the run method of another thread has completed its execution.

55. Concurrent ML is an extension to ML that includes a fform of threads and a form of synchronous message passing to support concurrency.

56. The use of spawn primitive of CML is to take the function as its parameter and to create a thread.

57. The use of subprograms BeginInvoke and Endinvoke in F# is to call threads asynchronously.

60. What is the type of an F# heap-allocated mutatable variable?

A mutable heap-allocated variable is of type ref

63. The FORALL statement of High-Performance Fortran is to specifies a sequence of assignment statements that may be executed concurrently.

Problem Set

1. Explain clearly why a race condition can create problems for a system.

Race condition can create problems for a system, because two or more tasks are racing to use the shared resource and the behavior of the program depends on which task arrives first (and wins the race).

2. The different ways to handle deadlock:

– Ignoring deadlock

– Detection

– Prevention

– Avoidance

3. Busy waiting is a method whereby a task waits for a given event by continuously checking for that event to occur. What is the main problem with this approach?

Busy-waiting or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input or a lock is available. Spinning can also be used to generate an arbitrary time delay, a technique that was necessary on systems that lacked a method of waiting a specific length of time. Processor speeds vary greatly from computer to computer, especially as some processors are designed to dynamically adjust speed based on external factors, such as the load on the operating system. Busy waiting may loop forever and it may cause a computer freezing

Programming Language Concept – Chapter 12

2. What are the problems associated with programming using abstract data types?

In nearly all cases, the features and capabilities of the existing type are not quite right for the new use.
The type definitions are all independent and are at the same level.
4. What is message protocol?
The entire collection of methods of an object is called the message protocol, or message interface, of the object.

5. What is an overriding method?
An overriding method is a method that provide an operation in the subclass that is similar to one in the parent class, but is customized for objects of the subclass. For example, a parent class, Bird, might have a draw method that draws a generic bird. A subclass of Bird named Waterfowl could override the draw method inherited from Bird to draw a generic waterfowl, perhaps a duck.

7. What is dynamic dispatch?
Dynamic dispatch is the third characteristic (after abstract data types and inheritance) of object-oriented programming language which is a kind of polymorhphism provided by the dynamic binding of messages to method definitions.

8. What is an abstract method? What is an abstract class?
For example, suppose a program defined a Building class and a collection of subclasses for specific types of buildings, for instance, French_Gothic. It probably would not make sense to have an implemented draw method in Building. But because all of its descendant classes should have such an implemented method, the protocol (but not the body) of that method is included in Building. Such a method is often called an abstract method ( pure virtual method in C++). A class that includes at least one abstract method is called an abstract class (abstract base class in C++).

10. What is an inner class?
Inner classes are non-static classes that are nested directly in another class.

12. From where are Smalltalk objects allocated?
Smalltalk objects are allocated from the heap and are referenced through reference variables, which are implicitly dereferenced.

15. What kind of inheritance, single or multiple, does Smalltalk support?
Smalltalk supports single inheritance; it does not allow multiple inheritance.

19. How are C++ heap-allocated objects deallocated?
C++ heap-allocated objects are deallocated using destructor.

29. Does Objective-C support multiple inheritance?
No Objective-C doesn’t support it. (It supports only single inheritance).

33. What is the purpose of an Objective-C category?
The purpose of an Objective-C category is to add certain functionalities to different classes and also to provide some of the benefits of multiple inheritance, without the naming collisions that could occur if modules did not require module names on their functions.

38. What is boxing?
Boxing is primitive values in Java 5.0+ which is implicitly coerced when they are put in object context. This coercion converts the primitive value to an object of the wrapper class of the primitive value’s type.

39. How are Java objects deallocated?
By implicitly calling a finalizemethod when the garbage collector is about to reclaim the storage occupied by the object.

Problem Set

1 . What important part of support for inheritance is missing in Java?
Java does not support the private and protected derivations of C++. One can surmise that the Java designers believed that subclasses should be subtypes, which they are not when private and protected derivations are supported. Thus, they did not include them.

3. Compare the inheritance of C++ and Java.

In Java, all classes inherit from the Object class directly or indirectly. Therefore, there is always a single inheritance tree of classes in Java, and Object class is root of the tree. In Java, if we create a class that doesn’t inherit from any class then it automatically inherits from Object Class. In C++, there is forest of classes; when we create a class that doesn’t inherit from anything, we create a new tree in forest.
In Java, members of the grandparent class are not directly accessible.
The meaning of protected member access specifier is somewhat different in Java. In Java, protected members of a class “A” are accessible in other class “B” of same package, even if B doesn’t inherit from A (they both have to be in the same package)
Java uses extends keyword for inheritence. Unlike C++, Java doesn’t provide an inheritance specifier like public, protected or private. Therefore, we cannot change the protection level of members of base class in Java, if some data member is public or protected in base class then it remains public or protected in derived class. Like C++, private members of base class are not accessible in derived class.
Unlike C++, in Java, we don’t have to remember those rules of inheritance which are combination of base class access specifier and inheritance specifier.
In Java, methods are virtual by default. In C++, we explicitly use virtual keyword.
Java uses a separate keyword interface for interfaces, and abstract keyword for abstract classes and abstract functions.
Unlike C++, Java doesn’t support multiple inheritance. A class cannot inherit from more than one class. A class can implement multiple interfaces though.
– In C++, default constructor of parent class is automatically called, but if we want to call parametrized constructor of a parent class, we must use Initalizer list. Like C++, default constructor of the parent class is automatically called in Java, but if we want to call parametrized constructor then we must use super to call the parent constructor
5. Compare abstract class and interface in Java.

First and major difference between abstract class and interface is that, abstract class is a class while interface is a interface, means by extending abstract class you can not extend another class becauseJava does not support multiple inheritance but you can implement multiple inheritance in Java.
Second difference between interface and abstract class in Java is that you can not create non abstract method in interface, every method in interface is by default abstract, but you can create non abstract method in abstract class. Even a class which doesn’t contain any abstract method can be abstract by using abstract keyword.
Third difference between abstract class and interface in Java is that abstract class are slightly faster than interface because interface involves a search before calling any overridden method in Java. This is not a significant difference in most of cases but if you are writing a time critical application than you may not want to leave any stone unturned.
Fourth difference between abstract class vs interface in Java is that, interface are better suited for Type declaration and abstract class is more suited for code reuse and evolution perspective.
Another notable difference between interface and abstract class is that when you add a new method in existing interface it breaks all its implementation and you need to provide an implementation in all clients which is not good. By using abstract class you can provide default implementation in super class.
10. Explain one advantage of inheritance.
Inheritance offers a solution to both the modification problem posed by abstract data type reuse and the program organization problem. If a new abstract data type can inherit the data and functionality of some existing type, and is also allowed to modify some of those entities and add new entities, reuse is greatly facilitated without requiring changes to the reused abstract data type. Programmers can begin with an existing abstract data type and design a modified descendant of it to fit a new problem requirement. Furthermore, inheritance provides a framework for the definition of hierarchies of related classes that can reflect the descendant relationships in the problem space.

12. Compare inheritance and nested classes in C++. Which of these supports an is-a relationship?
Inheritance is where one class (child class) inherits the members of another class (parent class).Nested class is a class declared entirely within the body of another class or interface.

Inheritance does.

17. What are the different options for object destruction in Java?
Finalize is related to C++ destructor. A finalize method is implicitly called when the garbage collector is about to reclaim the storage occupied by the object. The problem with finalize is that the time it will run cannot be forced or even predicted. The alternative to using finalize to reclaim resources held by an object about to be garbage collected is to include a method that does the reclamation. The only problem with this is that all clients of the objects must be aware of this method and remember to call it.

20. Compare the way Smalltalk provides dynamic binding with that of C++.
In C++, the programmer can specify whether static binding or dynamic binding is to be used. Because static binding is faster, this is an advantage for those situations where dynamic binding is not necessary. Furthermore, even the dynamic binding in C++ is fast when compared with that of Smalltalk. Binding a virtual member function call in C++ to a function definition has a fixed cost, regardless of how distant in the inheritance hierarchy the definition appears. Calls to virtual functions require only five more memory references than statically bound calls (Stroustrup, 1988). In Smalltalk, however, messages are always dynamically bound to methods, and the farther away in the inheritance hierarchy the correct method is, the longer it takes. The disadvantage of allowing the user to decide which bindings are static and which are dynamic is that the original design must include these decisions, which may have to be changed later.

21. Compare the support for polymorphism in C# with that of in Objective-C.
In Objective-C, polymorphism is implemented in a way that differs from the way it is done in most other common programming languages. A polymorphic variable is created by declaring it to be of type id. Such a variable can reference any object. The run-time system keeps track of the class of the object to which
an id type variable refers. If a call to a method is made through such a variable, the call is dynamically bound to the correct method, assuming one exists.
To allow dynamic binding of method calls to methods in C#, both the base method and its corresponding methods in derived classes must be specially marked. The base class method must be marked with virtual, as in C++. To make clear the intent of a method in a subclass that has the same name and protocol as a virtual method in an ancestor class, C# requires that such methods be marked override if they are to override the parent class virtual method.

25. Study and explain private and public modifiers in C++. How do those modifiers differ in C#?
C++ includes both classes and structs, which are nearly identical constructs. The only difference is that the default access modifier for class is private, whereas for structs it is public. C# also has structs, but they are very different from those of C++. In C#, structs are, in a sense, lightweight classes. They can have constructors, properties, methods, and data fields and can implement interfaces but do not support inheritance.

Programming Language Concept – Chapter 11

1. Two kinds of abstractions in programming languages are process abstraction and data abstraction.

5. The first design issue for abstract data types is the form of the container for the interface to the type. The second design issue is whether abstract data types can be parameterized. The third design issue is what access controls are provided and how such controls are specified.

6. Explain how information hiding is provided in an Ada package.
There are two approaches to hiding the representation from clients in the package specification. One is to include two sections in the package specification—one in which entities are visible to clients and one that hides its contents.

9. Package specification, is an Ada package which provides the interface of the encapsulation (and perhaps more)
Body package, is an Ada package which provides the implementation of most, if not all, of the entities named in the associated package specification.

10. The ‘with’ clause in Ada makes the names defined in external packages visible.

15. The purpose of a C++ destructor is to deallocate heap space (memory) that the object or class used.

16. A destructor has no return types.

20. Limited private types are useful when the usual predefined operations of assignment and comparison are not meaningful or useful.

21. Intializers in Objective-C are constructors.

26. The purpose of a Destructor is usually to clear off unused variables and clean up the memory. Java has in built memory handling mechanisms (Garbage collection) that clear off unused memory automatically. Hence there is no requirement for destructor methods. So that Java doesn’t need any destructor

27. Methods in Java must be defined completely in a class.

28. Java classes are allocated from the heap and accessed through reference variables.

PROBLEM SET

2. Suppose someone designed a stack abstract data type in which the function top returned an access path (or pointer ) rather than returning a copy of the top element. This is not a true data abstraction. Why ? Give an example that illustrates the problem.

– The problem with this is that the user is given access to the stack through the returned value of the “top” function. For example, if p is a pointer to objects of the type stored in the stack, we could have:

p = top(stack1);

*p = 42;

These statements access the stack directly, which violates the principle of a data abstraction.

4. The advantages of the nonpointer concept in Java?

• There is no memory leak such as dangling pointers or unnamed variables.

• Memory access via pointer arithmetic – this is fundamentally unsafe. Java has a robust security model and disallows pointer arithmetic for this reason.

• Array access via pointer offsets – Java does this via indexed array access so you don’t need pointers. A big advantage of Java’s indexed array access is that it detects and disallows out of bounds array access, which can be a major source of bugs.

• References to objects – Java has this, it just doesn’t call them pointers. Any normal object reference works as one of these.

8. Some drawbacks of user-defined generic classes in Java 5.0 are: for one thing, they cannot store primitives. Second, the elements cannot be indexed. Elements must be added to user-defined generic collections with the add method.

9. If the constuctor is absent in Java and C++, it will be automatically made by the compiler.

11. Destructors in C# are rarely used because it uses garbage collection for most of its heap objects.

12. Classes in Ruby are dynamic in the sense that members can be added at any time. This is done by simply including additional class definitions that specify the new members.

Programming Language Concept – Chapter 10

Review Question

1. By “simple” it means that subprograms cannot be nested and all local variables are static

2. Which of the caller of callee saves execution status information ?

-Either can save the execution status

3. Execution status information be stored for the linkage to a subprogram

4. What is the task of a linker?
Its first task is to find the files that contain the translated subprograms referenced in that program and load them into memory. Then, the linker must set the target addresses of all calls to those subprograms in the main program to the entry addresses of those subprograms.

6. What is the difference between an activation record and an activation record instance?
An activation record is the format, or layout, of the moncode part of a subprogram, whereas an activation record instance is a concrete example of an activation record, a collection of data in the form of an activation record.

8. What kind of machines often use registers to pass parameters?
RISC machines, parameters are passed in registers

11. What is an EP, and what is its purpose?
EP is a point or first address of the activation record instance of the main program. It is required to control the execution of a subprogram.

14. What are two potentialproblems with the static-chain method?
• It is difficult for a programmer working on a time-critical program to estimate the costs of nonlocal references, because the cost of each reference depends on the depth of nesting between the reference and the scope of declaration.
• Subsequent code modifications may change nesting depths, thereby changing the timing of some references, both in the changed code and possibly in code far from the changes.

Problem Set

6. Although local variables in Java methods are dynamically allocated at the beginning of each activation, under what circumstances could the value of a local variable in a particular activation retain the value of previous activation?
If the variable is declared as static. Static modifier is a modifier that makes a variable history – sensitive.

7. It is stated in this chapter that when nonlocal variables are accessed in a dynamic-scoped language using the dynamic chain, variable names must be stored in the activation records with the values. If this were actually done, every nonlocal access would require a sequence of costly string comparisons on names. Design an alternative to these string comparisons that would be faster.

Using approach that uses an auxiliary data structure called a display. Or, to write variable names as integers. These integers act like an array. So when the activation happens, the comparisons will be faster.

8. Pascal allows gotos with nonlocal targets. How could such statements be handled if static chains were used for nonlocal variable access? Hint:Consider the way the correct activation record instance of the static parent of a newly enacted procedure is found(see Section 10.4.2).

Based on the hint statement, the target of every goto in a program could be represented as an address and a nesting_depth, where the nesting_depth is the difference between the nesting level of the procedure that contains the goto and that of the procedure containing the target. Then, when a goto is executed, the static chain is followed by the number of links indicated in the nesting_depth of the goto target. The stack top pointer is reset to the top of the activation record at the end of the chain.

9. The static-chain method could be expanded slightly by using two static links in each activation record instance where the second points to the static grandparent activation record instance. How would this approach affect the time required for subprogram linkage and nonlocal references?

Including two static links would reduce the access time to nonlocals that are defined in scopes two steps away to be equal to that for nonlocals that are one step away. Overall, because most nonlocal references are relatively close, this could significantly increase the execution efficiency of many programs.

11. If a compiler uses the static chain approach to implementing blocks, which of the entries in the activation records for subprograms are needed in the activation records for blocks?

There are two options for implementing blocks as parameterless subprograms: One way is to use the same activation record as a subprogram that has no parameters. This is the most simple way, because accesses to block variables will be exactly like accesses to local variables. Of course, the space for the static and dynamic links and the return address will be wasted. The alternative is to leave out the static and dynamic links and the return address, which saves space but makes accesses to block variables different from subprogram locals

Programming Language Concept – Chapter 9

1. What are the three general characteristics of subprograms?
• Each subprogram has a single entry point.
• The calling program unit is suspended during the execution of the called
subprogram, which implies that there is only one subprogram in execution
at any given time.
• Control always returns to the caller when the subprogram execution
terminates.

2. What does it mean for a subprogram to be active?
A subprogram is said to be active if, after having been called, it has begun execution but has not yet completed that execution.

3. What is given in a header of a subprogram?
A subprogram header, which is the first part of the definition, serves several purposes. First, it specifies that the following syntactic unit is a subprogram definition of some particular kind.1 In languages that have more than one kind of subprogram, the kind of the subprogram is usually specified with a special word. Second, if the subprogram is not anonymous, the header provides a name for the subprogram. Third, it may optionally specify a list of parameters.

4. What characteristic of Python subprograms sets them apart from those of other languages?
One characteristic of Python functions that sets them apart from the functions of other common programming languages is that function def statements are executable. When a def statement is executed, it assigns the given name to the given function body. Until a function’s def has been executed, the function cannot be called. Consider the following skeletal example:
if . . .
def fun(. . .):
. . .
else
def fun(. . .):
. . .

5. What languages allow a variable number of parameters?
C# allows methods to accept a variable number of parameters, as long as they are of the same type.

6. What is a Ruby array formal parameter?
Ruby supports a complicated but highly flexible actual parameter configuration. The initial parameters are expressions, whose value objects are passed to the corresponding formal parameters. The initial parameters can be following by a list of key => value pairs, which are placed in an anonymous hash and a reference to that hash is passed to the next formal parameter. These are used as a substitute for keyword parameters, which Ruby does not support. The hash item can be followed by a single parameter preceded by an asterisk. This parameter is called the array formal parameter.

23. What is Automatic Generalization?
The type inferencing system of F# is not always able to determine the type of parameters or the return type of a function. When this is the case, for some functions, F# infers a generic type for the parameters and the return value. This is called automatic generalization.

24. What is an overloaded subprogram?
An overloaded subprogram is a subprogram that has the same name as another subprogram in the same referencing environment.

25. What is ad hoc binding?
Ad hoc binding is when the environment of the call statement that passed the subprogram as an actual parameter.

26. What is multicast delegate?
All of the methods stored in a delegate instance are called in the order in which they were placed in the instance. This is called a multicast delegate.

30. What are the design issues for functions?
The following design issues are specific to functions:
• Are side effects allowed?
• What types of values can be returned?
• How many values can be returned?

31. What two languages allow multiple values to be returned from a function?
Ruby allows the return of more than one value from a method. Lua also allows functions to return multiple values.

Problem Set
3. Argue in support of the template functions of C++. How is it different from the template functions in other languages?
C++ templated classes are instantiated to become typed classes at compile time. For example, an instance of the templated Stack class, as well as an instance of the typed class, can be created with the following declaration:
Stack myIntStack;
However, if an instance of the templated Stack class has already been created for the int type, the typed class need not be created.

6 . Compare and contrast PHP’s parameter passing with that of C#.
PHP’s parameter passing is similar to that of C#, except that either the actual parameter or the formal parameter can specify pass-by-reference. Passby- reference is specified by preceding one or both of the parameters with an ampersand.

8 . Argue against the Java design of not providing operator overloading
Arithmetic operators are often used for more than one purpose. For example, + usually is used to specify integer addition and floating-point addition. Some languages—Java, for example—also use it for string catenation. This multiple use of an operator is called operator overloading and is generally thought to be acceptable, as long as neither readability nor reliability suffers.

12 . Research Jensen’s Device, which was a widely known use of pass-by-name parameters, and write a short description of what it is and how it can be used.
Implementing a pass-by-name parameter requires a subprogram to be passed to the called subprogram to evaluate the address or value of the formal parameter. The referencing environment of the passed subprogram must also be passed. This subprogram/referencing environment is a closure. Pass-by-name parameters are both complex to implement and inefficient. They also add significant complexity to the program, thereby lowering its readability and reliability. Because pass-by-name is not part of any widely used language, it is not discussed further here. However, it is used at compile time by the macros in assembly languages and for the generic parameters of the generic subprograms in C++, Java 5.0, and C# 2005.

15. How is the problem of passing multidimensional arrays handles by Ada?
Ada compilers are able to determine the defined size of the dimensions of all arrays that are used as parameters at the time subprograms are compiled. In Ada, unconstrained array types can be formal parameters. An unconstrained array type is one in which the index ranges are not given in the array type definition. Definitions of variables of unconstrained array types must include index ranges. The code in a subprogram that is passed an unconstrained array can obtain the index range information of the actual parameter associated with such parameters

Programming Language Concept – Chapter 8

1. What is definition of control structure?

Control Structure : Control statement and the collection of statements whose execution it controls.

2. What did Bohm and Jocopini prove about flowchart?The algorithms that can be expressed by flowcharts can be coded in a programming language with only two control statements: one for choosing between two control flow paths and one for logically controlled iterations.

3. What is the definition of block?

Block : An anonymous method that is sent to the method (whose call precedes it) as a parameter

4. What is/are the design issue(s) for all selection and iteration control statements?

There is only one design issue that is relevant to all of the selection and iteration control statements: Should the control structure have multiple entries?

9. What are the design issues for multiple-selection statement?

The following is a summary of these design issues:

-What is the form and type of the expression that controls the selection?

– How are the selectable segments specified?

– Is execution flow through the structure restricted to include just a single selectable segment?

– How are the case values specified?

– How should unrepresented selector expression values be handled, if at all?

12. On what previous language was C’s switch statement based?

C’s switch statement is based from the ALGOL 68.

14. What are the design issues for all iterative control statement

– How is the iteration controlled?

– Where should the control mechanism appear in the loop statement?

21. What are the design issues for logically controlled loop statements?

The design issues are whether the control should be pretest/posttest and whether the logically controlled loop should be a special form of a counting loop or a separate statement.

23. What are the design issues for user-located loop control mechanisms?

The design issues for such a mechanism are the following:

– Should the conditional mechanism be an integral part of the exit?

– Should only one loop body be exited, or can enclosing loops also be exited?

29. How are iterator implemented in Ruby?

Ruby predefines several iterator methods, such as times and upto for counter-controlled loops and each for simple iterations of arrays and also the hashes too.

PROBLEM SET

1. What design issues should be considered for two-way selection statements?

The design issues for two-way selectors can be summarized as follows:

• What is the form and type of the expression that controls the selection?

• How are the then and else clauses specified?

• How should the meaning of nested selectors be specified?

2. Python uses indentation to specify compound statements. Give an example in support of this statement!

Python uses indentation to specify compound statements. For example,

if a > b :

a = b

print “case 7″

3. How can a straightforward grammar for a two-way selector statement lead to the problem of syntactic ambiguity? Give an example!

That ambiguous grammar was as follows:

if→ then

| if then else

The issue was when a selection statement is nested in the then clause of a selection statement, it is not clear to which, if an else clause should be associated.

14. State one of the main legitimate needs for gotos!

Premature exits from loops.