Chapter 15 Review

REVIEW

2. What does a lambda expression specify?

The predicate function is often given as a lambda expression, which in ML is defined exactly like a function, except with the fn reserved word, instead of fun, and of course the lambda expression is nameless.

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?

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 stands 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: The function that 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

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Chapter 14 Review

REVIEW

6 . What is exception propagation in Ada?

Exception propagation in Ada: A propagation that allows an exception raised in one program unit to be handled in some other unit in its dynamic or static ancestry. 

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

The scope of exception handlers in Ada: The exception that 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?

Four exceptions that are defined in the Standard package of Ada:

Constraint_aError

Program_Error

Storage_Error

Tasking_Error

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: 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.

Chapter 13 Review

REVIEW


1. What are the three possible levels of concurrency in programs?

Three possible levels of concurrency:
– 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)


7. What is the difference between physical and logical concurrency?

Physical concurrency: Several program units from the same program that literally execute simultaneously

Logical concurrency:  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?

The work of a scheduler is a scheduler that manages the sharing of processors among the tasks.

12. What is a heavyweight task? What is a lightweight task?

Heavyweight Task: The task that executes in its own address space.

Lightweight Task: The tasks that run in the same address space.

16. What is a task descriptor?

Task descriptor: 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 mark the task that its finished with its job but is not terminated yet.

34. What does the Java sleep method do?

The Java sleep method blocks the the thread.

35. What does the Java yield method do?

Java 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: 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 each processor has its own memory.

PROBLEM SET

1. Explain clearly why a 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. The importance of competition synchronization should now be clear.

2. What are the different ways to handle deadlock?

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: 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 very 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.

Chapter 12 Review

REVIEW

 

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

-The features and capabilities of the existing type are not really understanding by the beginner
-The type definitions are all independent and at the same level

4. What is message protocol?
Message protocol: The entire collection of methods of an object.

5. What is an overriding method?
Overriding method: A method that overrides the inherited method.

7. What is dynamic dispatch?
Dynamic dispatch: The third characteristic of object-oriented programming language which is a kind of polymorhphism provided by the dynamic binding of messages.

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, it doesn’t. Objective-C is not support it. It supports the single inheritance only.

33. What is the purpose of an Objective-C category?
The purpose of an Objective-C category: 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

3. Compare the inheritance of C++ and Java!
Java
:
– All classes inherit from the Object class directly or indirectly
– If we create a class that doesn’t inherit from any class, then it automatically inherits from Object Class
– Members of the grandparent class are not directly accessible
– Protected members of a class “A” are accessible in other class “B” of same package, even if B doesn’t inherit from A
– Java uses extends keyword for inheritance
– We don’t have to remember those rules of inheritance which are combination of base class access specifier and inheritance specifier
– Methods are virtual by default
– Uses a separate keyword interface for interfaces and abstract keyword for abstract classes and abstract functions

C++:
– Private members of base class are not accessible in derived class
– Have the forest of classes. When we create a class that doesn’t inherit from anything, we create a new tree in forest
– Support the multiple inheritance
– Default constructor of parent class is automatically called, but if we want to call parametrized the constructor of a parent class, we
must use Initalizer list
– Use virtual keyword


5. Compare abstract class and interface in Java!
– Abstract class is a class while interface is a interface, means by extending abstract class you can not extend another class because Java does not support multiple inheritance but you can implement multiple inheritance in Java.

– 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.

– The abstract class are slightly faster than interface because interface involves a search before calling any overridden method in Java

– The interface are better suited for Type declaration and abstract class is more suited for code reuse and evolution perspective

– 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

7. What is one programming situation where multiple inheritance has a significant disadvantage over interfaces?
A situation when there are two classes derived from a common parent and those two derived class has one child.


9. Give an example of inheritance in C++, where a subclass overrides the superclass methods!
class ship{

 public:
void sink(){
cout << “sink” << endl;
 }
 };
class titanic:public class ship{
 public:
void sink()
 {
 cout << “Sink! Titanic has been fallen!” << endl;
 }
 }


10. Explain one advantage of inheritance!
Provides a framework for the definition of hierarchies of related classes that can reflect the descendant relationship 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.

17. What are the different options for object destruction in Java?
There is no explicit deallocation operator.

Chapter 11 Review

REVIEW

2. Define abstract data type!
Abstract Data Type: The declarations of the type and the protocols of the operations on objects of the type, which provide the type’s interfaces contained in a single syntactic unit.

10. What is the use of the Ada with clause?
With clause makes the names defined in external packages visible.

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?
C++ is have a few encapsulations.

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 destructor?
Destructor has no return types.

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

22. What is the use of @private and @public directives?
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?
Friends Function: A “friend” of a given class is allowed access to public, private, or protected data in that class.
Friend Class: Class that can access the private and protected members of the class in which it is declared as a friend.

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
– By the complex pointer manipulation on array pointers, you can access arrays by their arithmetic indices
– Can checks all array indexing to ensure indices within the bounds of the array
– You no longer have dangling pointers and trashing of memory

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

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!
In my opinion, that’s not a good idea because it might be not become efficient.

Chapter 10 Review

REVIEW

1. What are the two reasons why implementing subprograms with stack-dynamic local variables is more difficult than implementing simple sub-programs?
– A stack-dynamic local variable is more complex activation records
– Recursion must be supported

2. What is the difference between an activation record and activation record instance?
Activation record: The Format, or layout, of the non-code part of a subprogram

An activation record instance stores all the information about subprogram calls, activation records stores the following data:
– Return address
– Static link  to the static parent
– Dynamic link  to the caller of this subprogram.
– Parameters
– Local variables

4. What are the two steps in locating a nonlocal variable in a static-scoped language with stack-dynamic local variables and nested subprograms?
– Find the correct activation record instance
– Determine the correct offset within that activation record instance

5. Define static chain, static depth, nesting depth, and chain offset!

Static chain: Chain of static links that connects certain activation record instances

Static depth: Integer associated with a static scope representing the scope’s nesting depth

The chain offset or nesting depth of a non-local reference is the difference between the static depth of the reference and that of the scope where it is declared.

6. What are the two potential problems with the static chain methods?
– A non-local reference is slow if the number of scopes between the reference and the declaration of the referenced variable is large
– Time critical code is difficult, because the costs of non-local references are not equal, and can change with code upgrades and fixes

7.  What is display?

One alternative to static chain is to use a display, for this approach, the static links are collected in a single array called a display. Display uses a pointer array to store the activation records along the static chain.

10. Explain the two methods of implementing block?

Blocks are treated as parameter less subprograms that are always called from the same place in the program.

Block can also be implemented in a different and somewhat simpler and more efficient way. The maximum amount of storage required for block variables at any time during the exaction of program can be statically determined, because block are entered and exited in strictly textual order.

11. Describe the deep access method of implementing dynamic scoping?

Deep Access -> nonlocal references are found by searching the activation record instances on the dynamic chain. Length of chain cannot be statically determined every activation record instance must have variable names

12. Describe the shallow access method of implementing dynamic scoping?

In case of shallow access names and values are stored in a global table. Using this method, space is allocated for every variable name that is in the program. When a sub-routine is called it saves the current value of the variable and replaces it with the value in its current scope and restores the value of the variable while exiting.

14.  Compare the efficiency of the deep access method to that of the shallow access method, in term of both call and non-local access?

The deep access methods provides fast subprogram linkage, but references to non-local, especially references to distant non-locals are costly. The shallow access methods provide much faster references to nonlocals, especially distant nonlocals, but are more costly in term of subprogram linkage.

PROBLEM SET

7. It 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!

One very simple alternative is to assign integer values to all variable names used in the program. Then the integer values could be used in the activation records, and the comparisons would be between integer values, which are much faster than string comparisons.

8. Pascal allows gotos with nonlocal targets. How could such statements be handled if static chains were used for nonlocal variable access?

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. 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.

 

Chapter 9 Review

Review

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 to be active means that after having been called, it has begun execution but has not yet complete execution.

4. What are formal parameters? What are actual parameters?
–  Formal parameters: The parameters in the subprogram header
– Actual parameters:  The parameters that the call statements must including the name of the subprogram and list of parameters to be bound to the formal parameters of the subprogram

 

5. What are the advantages and disadvantages of keyword parameters?
– Advantage: Can appear in any order in the actual parameter list
– Disadvantage:  User of the subprogram must know the names of formal parameters

6. What are the design issues for subprograms?
– What parameter-passing method or methods are used
– Are local variable statically or dynamically allocated?
– Can subprogram definitions appear in other subprogram definitions?
– Can a subprogram be overloaded?
– Can subprograms be generic?

7. What are the advantages and disadvantages of dynamic local variables?
Advantages:
– They provide flexibility to the subprogram
– The storage of local variables in an active subprogram can be shared with the local variables in all inactive subprograms
– They efficiently used when computer has small memory (Faster Access)

Disadvantages:
– Cost of the time required to allocate
– Access to dynamic local variable must be indirect
– The stack dynamic local variables, subprograms cannot be history sensitive

10. In what ways can aliases occur with pass-by-reference parameters?
Aliases can be occurred because pass-by-reference makes access paths being available to called the subprograms.

17. What is parametric polymorphism?
Parametric polymorphism is provided by a subprogram that takes a generic parameter that is used in a type expression that describes the types of the parameters of the subprogram. Both ADA and C++ provides a kind of compile-time parametric polymorphism.

18.  What causes a C++ template function to be instantiated?
C++ template functions are instantiated implicitly when the function is named in a call or when its address is taken with the processor.

20. If a Java 5.0 method returns a generic type, what type of object is actually returned?
In Java any type or class can be returned by methods. Because methods are not types, they cannot be returned.

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 aqqqes an instance of the typed class, can be created with the following declaration:

Stack<int> 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.

 

7. Consider the following program written in C syntax:

void fun (int first, int second){
first += first;
second += second;
}
void main() {
int list [2] = {3,5};
fun(list[0], list[1]);
}

For each of the following parameter-passing methods, what are the values of the list array after execution?

a. Passes by value

b. Passes by reference

c. Passes by value-result

(a) 3, 5

(b) 6, 10

(c) 6, 10

11. Compare the use of closures by programming languages!
Nearly all functional programming languages, most scripting languages, and at least one primarily imperative language, C#, support closures. These languages are static-scoped, allow nested subprograms, and allow subprograms to be passed as parameters.

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.