Example Test Questions for Inheritance

Transcription

1 2009 November 23 Example Test Questions for Inheritance Give and explain the type rule with genericity using an example method call. escribe constraint genericity. How is such genericity related to inheritance? Provide an example where constraint genericity is useful. When you redefine a, you can redefine the signature and body indepently. Explain why you need redefinition of each part and what are the constraints on redefinition. When you redefine a, there are two parts of a you can redefine indepently. Explain what they are, why you need redefinition of each part and what are the constraints on redefinition? What is the rule of change in the context of deciding between use and inheritance? Give three natural language definitions and their corresponding Eiffel class definitions that illustrate the choices in deciding between use and inheritance? When using multiple inheritance sharing and replication of attributes are the choices that are available. Using a ON diagram, give an example where sharing is not an option. Explain why sharing is not an option. When using multiple inheritance sharing and replication of attributes are the choices that are available. Using a ON diagram, give an example where sharing and replication are options. Explain why sharing is an option and how you get sharing. Explain why replication is an option and how you get replication. When using multiple inheritance some s may be joined. Using a ON diagram, give an example where join is an option and explain under what conditions join is possible. Explain what happens to the export status of inherited s in an heir. Why would you not normally build the QUEUE class from the RRY class using inheritance? In Eiffel, inherited functions can be redefined as attributes but not vice versa. Why not? onsider the following inheritance diagram. What problems can arise and how can they resolved? You are not required to solve all problems simultaneously, just describe the various problems and their resolution.

2 2009 November 23 Sample Inheritance Test Questions Page 2 of 9 f, h, j ++ f g f g 13. onsider the following ON diagram. + PERSON work : T TEHER STUENT work ++ : T T 14. Give and explain one variation of the Eiffel inheritance and adaptation clauses for the class T that permit sharing the common. Give and explain a different variation of the Eiffel inheritance and adaptation clauses for the class T that permit sharing the common. Give and explain the Eiffel inheritance and adaptation clauses for the class T that permit replicating the common Using an example, explain static and dynamic types of an entity and how they relate. Explain polymorphism and dynamic binding.

3 2009 November 23 Sample Inheritance Test Questions Page 3 of Explain why the creation status of a in the parent has no bearing on the creation status of that in an heir. Explain the difference between renaming and redefining an inherited. Is the following inheritance scenario correct? If yes, state why. If not, state what is the problem and how it can be resolved? class [G] class inherit f: G [REL] [STRING] Given following class hierarchy: PERSON EMPLOYEE STUENT T and declaration and instructions: p : PERSON; e: EMPLOYEE; s : STUENT; t1, t2 : T create p.make( ); create s.make( ); create t1.make( ) are the following instructions valid? Give a reason for your answer. create PERSON t2.make( ) create T e.make( ) p := t1 s?= p 19. In the following design, the class STUENT_TRINEE is missing adaptation or other Eiffel inheritance statements, thereby introducing inconsistencies and errors. There is additional missing program text. Identify what is missing and supply Eiffel program text to correct the program. ssume the given rename and redefine statements are correct. class PERSON eat (what: FOO) is print ("I eat sometimes!") sleep is print ("I sleep sometimes!") play is print ("I play sometimes!") -- class PERSON class EMPLOYEE inherit PERSON rename play as work redefine eat eat (what: STEK) is class STUENT inherit PERSON rename play as study redefine eat eat (what: SNWIH) is print ("I eat sandwich!") -- class STUENT class STUENT_TRINEE inherit STUENT redefine work, eat EMPLOYEE redefine eat

4 2009 November 23 Sample Inheritance Test Questions Page 4 of 9 print ("I eat steak!") -- class EMPLOYEE class FOO -- class FOO eat (what: STEK_SNWIH) is print ("I eat well!") -- class STUENT_TRINEE class STEK inherit FOO -- class STEK class SNWIH inherit FOO -- class SNWIH The creation inheritance rule states that the creation status of a in the parent has no bearing on its creation status in an heir. Explain what this means and why it is a reasonable rule. In the following diagram class inherits two versions of "f": one from and a redefined version from. ased on whether "f " is deferred or not, discuss the problems associated with "f" in and how they can be resolved. f f onsider the following program text. class ITY the_city: ITY is once Result := urrent invariant lonely_city: the_city = urrent -- class ITY class LONON inherit ITY -- class LONON class TORONTO inherit ITY -- class TORONTO ssuming the class invariant is checked, es the execution of the following statements lead to any assertion violation in Eiffel? Justify your answer. city1, city2 : ITY toronto: TORONTO lonn: LONON

5 2009 November 23 Sample Inheritance Test Questions Page 5 of 9 create toronto create lonn city1 := lonn.the_city city2 := toronto.the_city 23. ssume class LONON, from part, is modified as defined below. raw memory diagrams for objects created as a result of execution of the set of statements in Part above. ssume assertions are turned on. class LONON inherit ITY redefine the_city the_city: LONON is once Result := urrent -- class LONON onsider the following program text. class THING the_thing: THING is once Result := urrent invariant only_thing: the_thing = urrent class ETTER inherit SOMETHING class WORSE inherit SOMETHING ssuming the class invariant is checked, es the execution of the following statements lead to any assertion violation in Eiffel? Justify your answer. thing_1, thing_2 : THING the_worse: WORSE the_better: ETTER create the_worse create the_better thing_1 := the_better.the_thing thing_2 := the_worse.the_thing ssume class ETTER, from part, is modified as defined below. raw memory diagrams for objects created as a result of execution of the set of statements in Part above. ssume assertions are turned on. class ETTER inherit SOMETHING redefine the_thing the_thing: ETTER is once Result := urrent 24. The following hierarchy defines players in baseball.

6 2009 November 23 Sample Inheritance Test Questions Page 6 of 9 ssume that PITHER introduces a starts (indicating the number of games the pitcher started), while the class PLYER introduces a deferred display that is implemented by the subtypes. LOSER is a special kind of pitcher, one who always finishes games. Show the inheritance clause for LOSER, including and redefine and export clauses. Supose you wanted to modify this design to handle designated hitters, players who only hit and not play infield or outfield. What changes would you suggest to the hierarchy? In the National League, pitchers also hit. Show modifications to the inheritance hierarchy that would take into account National League pitchers and merican League pitchers (who not hit). team has a set of players. Sketch an Eiffel implementation of a routine that would display all the players on a team. 25. Suppose you wrote the following four classes but you haven t tried to compile them. onsider how the class ELT can handle possible name clashes. deferred class LPH one is print( alpha one ) two is print( alpha two ) three is print( alpha three ) four is deferred deferred class ET inherit LPH redefine two two is print( beta two )

7 2009 November 23 Sample Inheritance Test Questions Page 7 of 9 class HRLIE inherit LPH redefine two, three two is print( charlie two ) three is print( charlie three ) four is print( charlie four ) class ELT inherit ET rename one as beta_one HRLIE rename one as charlie_one select four The answers to the following questions require either a yes or no, as appropriate, and must give a rationale that references appropriate rules or principles. yes or no without a rationale receives a zero grade. 26. Is it necessary for class ELT to include the procedure one in a rename clause? If so, please explain why. If not, please explain why not. Is it acceptable for class ELT to not refer to the procedure two in a rename, redefine, undefine, or select clause? If so, you must explain why. If not, you must explain why not, and describe one way in which the problem can be resolved. Is it acceptable for class ELT to not refer to the procedure three in a rename, redefine, undefine, or select clause? If so, you must explain why. If not, you must explain why not, and describe one way in which the problem can be resolved. Is it necessary for class ELT to refer to the procedure four in a select clause? If so, please explain why. If not, please explain why not. onsider the following class hierarchy and program text. p : PERSON; t : TEHER; s : STUENT; ta1, ta2 : T create p.make( ) create s.make( ) create ta1.make( ) 27. For each of the following instructions state whether or not the instruction is valid and give the reason why. 1) create {PERSON} ta2.make( ) 2) create {T} t.make( ) 3) p := ta1 4) s?= p ) We learned that software modeling is difficult: by changing our view point we can rephrase an "isa" relationship to a "has-a" relationship. For example "every software engineer is an engineer" can be rephrased as "every software engineer has an engineer component", therefore changing "inheritance"

8 2009 November 23 Sample Inheritance Test Questions Page 8 of relationship to "client-supplier". iscuss what criteria can be used, in such situations, to decide whether is-a or has-a is the most appropriate relation for the chosen entities. ) We have two relations between classes: client-supplier and inheritance. ompare these two relations in terms of reuse, information hiding and protection against change. That is to say which one of these relationships allow for reuse of services provided by a class, which allows for information hiding, and which protects a class against change. Justify your answers. ) In Eiffel a descent can redefine a function with no argument into an attribute, but not vice versa. First explain why it is not possible to redefine an attribute into a function. Then explain how a descent defining a function into an attribute should handle the postcondition of that function. With multiple inheritance sharing and replication of s are the choices that are available. Using a ON diagram, give an example where sharing and replication are options. Explain why sharing is an option and give the Eiffel program text that enables sharing. Explain why replication is an option and give the Eiffel program text that enables replication.. With multiple inheritance sharing and replication of attributes are the choices that are available. Using a ON diagram, give an example where sharing is not an option. Explain why sharing is not an option. nswer the following questions with respect to the program text given at the of the question. What would be the class invariant for class? Will the class invariant be satisfied immediately after creating an instance of create a.make. Justify your answer completely and in detail. ssume that all assertions are changed to true, what would be the result of executing the program text in the ROOT_LSS. Justify your answer completely and in detail. Is the redefinition of the printa in class correct. Justify your answer in detail by using the complete pre and post conditions to justify your conclusion. class creation make x : INTEGER y : INTEGER make is x := 2 ; y := 5 printa( a : INTEGER) is require y > x class inherit rename printa as c_print redefine uble creation make printa( a : INTEGER) is require true class ROOT_LSS creation make a : ; b : c : ; d : make is!! a.make ;!!b.make

9 2009 November 23 Sample Inheritance Test Questions Page 9 of 9 io.put_string("in a is: ") io.put_integer(a) ensure y - x > 0 uble : INTEGER is require y > 2 result := 2 * y + x ensure result > y + x invariant x > 1 io.put_string("in a is: ") io.put_integer(a) ensure true uble : INTEGER is require else y > 0 result := x + y - x*y ensure then result > x + y invariant y >= 5!! c.make ;!!d.make a.printa(a.uble) d := a d.printa(a.uble) class inherit redefine printa, make creation make z : INTEGER make is precursor ; z := -4 printa( a : INTEGER) is require else x > 0 io.put_string("in a is: ") io.put_integer(a) ensure then true invariant z < x or z > y y 5 > x class inherit rename printa as b_print redefine uble, make undefine make redefine uble select c_print creation make make is precursor uble := z + x + y uble : INTEGER invariant??? Eiffel has four mechanisms for adaptation. escribe and give an example of each one.. What is the rule of change in the context of deciding between use and inheritance?. Give three natural language definitions and their corresponding Eiffel class definitions that illustrate the choices in deciding between use and inheritance?