Concepts Of Programming Languages by Robert W. Sebesta Chapter 16, Logic Programming Language – Pg 779

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

1. What are 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. What are the two parts of a compound term?
– 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. What are the two modes in which a proposition can be stated?
– 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.

4. What is general form of a proposition in clausal form ?
-B1 U B2 U . . . U Bn C A1 n A2 n . . . n Am

5. What are antecedents? Consequents?
– 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.

6. Give general definitions of resolution and unification
– Resolution : inference rule that allows inferred propositions to be computed from given propositions, thus providing a method with potential application to automatic theorem proving.
Unification : Process of determining useful values for variables.

7. What are the forms of Horn clauses?
– 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 )

11. What is an uninstantiated variable?
– An uninstantiated variable is a variable that has not been assigned a value.

13. What is a conjunction?
– 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.

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.

Concepts Of Programming Languages by Robert W. Sebesta Chapter 15, Functional Programming Languages– Pg 740

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

3. What data types were parts of the original LISP?
– Atoms and list were the two data types in original LISP.

5. Explain why QUOTE is needed for a parameter that is a data list.
– To avoid evaluating a parameter, it is first given as a parameter to the primitive function QUOTE, which simply returns it without change.

6. What is a simple list?
– A list which membership of a given atom in a given list that does not include sublists.

7. What does the abbreviation REPL stand for?
-REPL stand for read-evaluate-print loop.

11. What are the two forms of DEFINE?
-The simplest form of DEFINE is one used to bind a name to the value of an expression. This form is (DEFINE symbol expression) The general form of such a DEFINE is (DEFINE (function_name parameters) (expression)

13. Why are CAR and CDR so named?
– The names of the CAR and CDR functions are peculiar at best. The origin of these names lies in the first implementation of LISP, which was on an IBM 704 computer. The 704’s memory words had two fields, named decrement and address, that were used in various operand addressing strategies. Each of these fields could store a machine memory address. The 704 also included two machine instructions, also named CAR (contents of the address part of a register) and CDR (contents of the decrement part of a register), that extracted the associated fields. It was natural to use the two fields to store the two pointers of a list node so that a memory word could neatly store a node. Using these conventions, the CAR and CDR instructions of the 704 provided efficient list selectors. The names carried over into the primitives of all dialects of LISP.

18. What is tail recursion? Why is it important to define functions that use recursion to specify repetition to be tail recursive?
– 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).

19. Why were imperative features added to most dialects of LISP?
– LISP began as a pure functional language but soon acquired some important imperative features to increased its execution efficiency.

26. What is type inferencing, as used in ML?
– Type inference refers to the automatic deduction of the type of an expression in a programming language. If some, but not all, type annotations are already present it is referred to as type reconstruction.

29. What is a curried function?
– Curried functions a function which a new functions can be constructed from them by partial evaluation.

30. What does partial evaluation mean?
– Partial evaluation means that the function is evaluated with actual parameters for one or more of the leftmost formal parameters.

32. What is the use of the evaluation environment table?
– 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.

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.

 

Problem Set

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.

9. What does the following Scheme function do?
(define ( y s lis)
(cond
(( null? lis) ‘ () )
((equal? s (car lis)) lis)
(else (y s (cdr lis)))
))

=> y returns the given list with leading elements removed up to but not including the first occurrence of the first given parameter.

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

Concepts Of Programming Languages by Robert W. Sebesta Chapter 14, Exception Handling and Event Handling – Pg 684

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

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.

 

Concepts Of Programming Languages by Robert W. Sebesta Chapter 13, Concurrency – Pg 645

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

1. What are the 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)

– Program level (executing two or more programs simultaneously)

7. What is the difference between physical and logical concurrency?
– 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. What is the work of a scheduler?
-Scheduler manages the sharing of processors among the tasks.

12. What is a heavyweight task? What is a lightweight task?
-Heavyweight task executes in its own address space. Lightweight task all run in the same address space.

16. What is a task descriptor?
– Task descriptor is a data structure that stores all of the relevant information about the execution state of a task.

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

21. What is a binary semaphore? What is a counting semaphore?
– Binary semaphore is a semaphore that requires only a binary-valued counter, like the one used to provide competition synchronization. A counting semaphore is a synchronization object that can have an arbitrarily large number of states.

30. What is purpose of an Ada terminate clause?
– The purpose of an Ada terminate clause is to mark that the task is finished with its job but is not yet terminated.

34. What does the Java sleep method do?
– Sleep method blocks the the thread.

35. What does the Java yield method do?
– Yield method surrenders the processor voluntarily as a request from the running thread.

36. What does the Java join method do?
– Java forces a method to delay its execution until the run method of another thread has completed its execution.

37. What does the Java interrupt method do?
– Interrupt becomes one way to communicate to a thread that it should stop.

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

56. What is the use of the spawn primitive of CML?
– The use of Spawn primitive of CML is to create a thread.

57. What is the use of subprograms BeginInvoke and EndInvoke in F#?
– The use of subprograms BeginInvoke and Endinvoke in F# is to call threads asynchronously.

58. What is the use of the DISTRIBUTE and ALIGN specification of HPC?
– The use of DISTRIBUTE and ALIGN specification of HPC is to provide information to the compiler on machines that do not share memory, that is, each processor has its own memory.

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Concepts Of Programming Languages by Robert W. Sebesta Chapter 12, Support for Object-Oriented Programming – Pg 590

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

3. What is the advantage of inheritance?

– It allows the new abstract data type to inherit the data and functionality of existing one. We can also apply some modification to it.

4. What is message protocol?
-Message protocol is the entire collection of methods of an object.

5. What is an overriding method?
– Overriding method is when a new method overrides the inherited method.

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.

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 finalize method when the garbage collector is about to reclaim the storage occupied by the object.

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Concepts Of Programming Languages by Robert W. Sebesta Chapter 11, Abstract Data Types and Encapsulation Constructs – Pg 538

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

1. What are the two kinds of abstractions in programming language?

– Process abstraction and data abstraction.

2. Define abstract data type.
Data type that satisfies the following conditions:
-The representation of objects of the type is hidden from the program units that use the type, so the only direct operations possible on those objects are those provided in the type’s definition.
-The declarations of the type and the protocols of the operations on objects of the type, which provide the type’s interface, are contained in a single syntactic unit. The type’s interface does not depend on the representation of the objects or the implementation of the operations. Also, other program units are allowed to create variables of the defined type.

8. What is the difference between private and limited private types in Ada?
– Limited private is more restricted form and objects of a type that is declared limited private have no built-in operations.

10. What is the use of the Ada with clause?
– With clause makes the names defined in external packages visible; in this case Ada. Text_IO, which provides functions for input of text.

11. What is the use of the Ada use clause?
– Use clause eliminates the need for explicit qualification of the references to entities from the named package.

12. What is the fundamental difference between a C++ class and an Ada package?
– Ada packages are more generalize encapsulations that can define any number of types.

15. What is the purpose of a C++ destructor?
– The purpose of a C++ desctructor is as a debugging aid, in which case they simply display or print the values of some or all of the object’s data members before those members are deallocated.

16. What are the legal return types of a desctructor?
-Destructor has no return types and doesn’t use return statements.

21. What are initializers in Objective-C?
– The initializers in Objective-C are constructors.

22. What is the use of @private and @public directives?
– The use is to specify the access levels of the instance variables in a class definition.

27. Where are all Java methods defined?
– All Java methods are defined in a class.

30. What is a friend function? What is a friend class?
– a “friend” of a given class is allowed access to public, private, or protected data in that class. Normally, function that is defined outside of a class cannot access such information. Class that can access the private and protected members of the class in which it is declared as a friend. On declaration of friend class all member function of the friend class become friends of the class in which the friend class was declared.

43. What is a C++ namespace, what is its purpose?
– In general, a namespace is a container for a set of identifiers and allows the disambiguation of homonym identifiers residing in different namespaces. The purpose is to help programs manage the problem of global namespace.

Problem Set

4. What are the advantages of the nonpointer concept in Java?
– Any task that would require arrays, structures, and pointers in C can be more easily and reliably performed by declaring objects and arrays of objects. Instead of complex pointer manipulation on array pointers, you access arrays by their arithmetic indices. The Java run-time system checks all array indexing to ensure indices are within the bounds of the array. You no longer have dangling pointers and trashing of memory because of incorrect pointers, because there are no pointers in Java.

9. What happens if the constructor is absent in Java and C++?
– It will be made automatically by the built-up in.

10. Which two conditions make data type “abstract” ?
– The representation, or definition, of the type and the operations are contained in a single syntactic unit
– The representation of objects of the type is hidden from the program units that use the type, so only direct operations possible on those objects are those provided in the type’s definition

17. The namespace of the C# standard library, System, is not implicitly available to C# programs. Do you think this is a good idea? Defend your answer.
=> I think it is not, because it reduces its efficiency.

19. Compare Java’s packages with Ruby’s modules.
– In Ruby, the require statement is used to import a package or a module. For example, the extensions package/module is imported as follows.
– require ‘extensions’
External files may be included in a Ruby application by using load or require. For example, to include the external file catalog.rb, add the following require statement.
-require “catalog.rb”
The difference between load and require is that load includes the specified Ruby file every time the method is executed and require includes the Ruby file only once.
In Java, the import statement is used to load a package. For example, a Java package java.sql is loaded as follows.

Concepts Of Programming Languages by Robert W. Sebesta Chapter 10, Implementing Subprograms – Pg 486

Review Questions

(Assignment by Mr Tri Djoko Wahyono)

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

4. What is the task of a linker?
– The task of a linker is to find the files that contain the translated subprograms referenced in that program and load them into memory.

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.

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.
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
the previous activation?
– If the variable is declared as static. Static modifier is a modifier that makes a variable history – sensitive.

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).
Following the hint stated with the question, 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.