Chapter 6 Programming Language Concepts R Sebesta

Nama: Stefanus Eduard Adrian
NIM: 1801382963

Kali ini saya akan menjawab Assignment #6 dari Chapter 6 Programming Language Concepts R Sebesta

Review Questions

6. What are the advantages of user-defined enumeration types?

*User-defined enumeration types are most useful when a data type can take one of a small, discrete set of values, each of which have some meaning that is not a number. A favorite example in textbooks is a type for the suit of a playing card. There are four options: SPADE, CLUB, HEART, DIAMOND, and so we would make an enumeration type with these four entries. The main advantages are efficiency in storage (compared to e.g. storing these values as strings) and more readable code.

7. In what ways are the user-defined enumeration types of C# more reliable than those of C++?

*Since C# enumeration types are not coerced into integer types, as the C++ does so, it's more reliable.

8. What are the design issues for arrays?

*-What types are legal for subscripts?

-Are subscripting expressions in elemnet refrence range checked?

-When are subscript ranges bound?

-When does allocation take place?

-What is the maximum number of subscripts?

-Can array objects be initialized?

-Are any kind of slices supported?

9. Define static, fixed stack-dynamic, stack-dynamic, fixed heap-dynamic, and heap-dynamic arrays. What are the advantages of each?

*Static array is an array which the subscript ranges are statically bound and storage allocation is static (before run-time). The advantage is efficiency (no dynamic allocation).

Fixed stack-dynamic array is an array which the subscript ranges are statically bound, but the allocation is done at declaration time. The advantage is space efficiency

Stack-dynamic array is an array which the subscript ranges are dynamically bound and the storage allocation is dynamic (done at run-time). The advantage is flexibility (the size of an array need not be known until the array is to be used).

Fixed heap-dynamic array is similar to fixed stack-dynamic, storage binding is dynamic but fixed after allocation (i.e., binding is done when requested and storage is allocated from heap, not stack). The advantage of fixed heap-dynamic array is flexibility (the array’s size always fits the problem).

Heap-dynamic array is an array which the binding of subscript ranges and storage allocation is dynamic and can change any number of times. The advantage is flexibility (arrays can grow or shrink during program execution).

10. What happens when a nonexistent element of an array is referenced in Perl?

*If an r-value is required, undef is returned. If an l-value is required, the array is extended, then the newly created but undefined element is returned. No error is reported.

Problem Set

6. Explain all of the differences between Ada’s subtypes and derived types.

*Ada’s subtype is compatible with its base type, so you can mix operands of the base type with operands of the base type. While Ada’s derived type is a completely separate type that has the same characteristics as its base type. We can’t mix operands of a derived type with operands of the base type.

7. What significant justification is there for the -> operator in C and C++?

*The only justification for -> operator in C and C++ is writability. It is slightly easier to write p->q than (*p).q.

8. What are all of the differences between the enumeration types of C++ and those of Java?

*In C++, an enumeration is just a set of named, integral constants. Also, C++ will implicitly convert enum values to their integral equivalent. In Java, an enumeration is more like a named instance of a class. You have the ability to customize the members available on the enumeration. Java will explicitly convert enum values to their integral equivalent.

9. The unions in C and C++ are separate from the records of those languages, rather than combined as they are in Ada. What are the advantages and disadvantages to these two choices?

*

	Union separated from records	Union combined with records
Advantages	-Reduce developer overhead (less checking) -Goes with the C++ design (C++ is not a weak strong typing language)	-Support type checking -Goes with the Ada design (Ada is strong typing language)
Disadvantages	-No type checking of references -May end with wrong or unexpected results	-Increase developer overhead -Using more functions to resolve type compatibility

10. Multidimensional arrays can be stored in row major order, as in C++, or in column major order, as in Fortran. Develop the access functions for both of these arrangements for three-dimensional arrays.

*Let the subscript ranges of the three dimensions be named min(1), min(2), min(3), max(1), max(2), and max(3). Let the sizes of the subscript ranges be size(1), size(2), and size(3). Assume the element size is 1.

Row Major Order:

 location(a[i,j,k]) = (address of a[min(1),min(2),min(3)]) + ((i-min(1))*size(3) + (j-min(2)))*size(2) + (k-min(3))

Column Major Order:

 location(a[i,j,k]) = (address of a[min(1),min(2),min(3)]) + ((k-min(3))*size(1) + (j-min(2)))*size(2) + (i-min(1))