Bertrand Meyer. Ei#el: The Language. Prentice Hall International, New York, 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....since each language has its own constructs that allow for implementation of OO mechanisms in more or less detail, a binding for the case studies language (C ) is included ahead . Similar bindings will be proposed for other OO languages in the near future. A validation experiment with Eiffel [Meyer92] is currently under way. This expected, but yet to be proved, language independence will broaden the applicability of this metric set by allowing comparison of heterogeneous system implementations. 3.2 A supporting example To help clarify the metrics determination process, the following C ....

Meyer B., Eiffel: The Language, Prentice Hall International, 1992.

....Each OO programming language has its own constructs that allow for implementation of OO mechanisms in somewhat distinct fashions. A mapping, hereafter referred as binding, of MOOD concepts and terminology to the adopted implementation language is thus needed. A binding for the Eiffel language [Meyer92] is included in this section. A binding for the C language was introduced in [Abreu95] Bindings for other OO languages are expected to be defined in the near future. This section will present a stepwise introduction of each relevant concept in MOOD, immediately followed by the corresponding ....

Meyer, B., Eiffel: The Language, Prentice Hall International, 1992.

....String are in no way related. In Python [vR01] on the other hand, C will contain only the method from A since it is interested solely in the name of the method as opposed to how many arguments it has and chooses which particular method to inherit on a left to right depth rst basis. Ei el [Mey92] renders this example invalid as it stands, and insists that each element in a class must have a unique name. Figure 1(b) is much trickier as both of the methods m in A and B have the same signature. We have already seen that Python will choose the m from A. Whereas C and UML could safely ....

Bertrand Meyer. Eiel: The Language. Prentice Hall International, 1992.

....browser presents various views of the class, including its name and position in the class hierarchy, a list of the functions it provides, and the complete source text with function and variable definitions. The organization of Eiffel is very similar to the one file model described in this paper [12, 13]. The developer of a class maintains a single file that contains all of the information about the class. The utility short extracts a human readable interface from the class document and the utility flatten shows all the features provided by a class independently of their origin in the class ....

Bertrand Meyer. Eiffel: the Language. Prentice Hall International, 1992.

....for which it is not important which exception is structurally first. Our semantics is presented in the context of Java, but it could be applied to other languages. The partial results feature may be particularly helpful in implementing the retry keyword in languages that have one, such as Eiffel [10]. This would allow the loop to restart at the point the logically first exception occurred, while keeping previously computed partial results. The ability to express concurrency in a clean and natural way is an important feature to have in modern programming languages. Parts of programs that ....

B. Meyer. Eiffel: The Language. Prentice Hall International, Hemel Hempstead, UK, 1992.

....semantics would be useful or would make programs more understandable. Our semantics is presented in the context of Java, but it could be applied to other languages. The partial results feature may be particularly helpful in implementing the retry keyword in languages that have one, such as Ei#el [23]. This would allow the loop to restart at the point the logically first exception occurred, while keeping previously computed partial results, and should greatly simplify the try. repair. retry pattern described in the examples. The ability to express concurrency in a clean and natural way is an ....

B. Meyer. Ei#el: The Language. Prentice Hall International, Hemel Hempstead, UK, 1992.

....for which it is not important which exception is structurally rst. Our semantics is presented in the context of Java, but it could be applied to other languages. The partial results feature may be particularly helpful in implementing the retry keyword in languages that have one, such as Ei el [17]. This would allow the loop to restart at the point the logically rst exception occurred, while keeping previously computed partial results. The ability to express concurrency in a clean and natural way is an important feature to have in modern programming languages. Parts of programs that ....

Meyer, B.: Eiel: The Language. Prentice Hall International, Hemel Hempstead, UK (1992)

....additional constraints would be implicit and could be viewed as a kind of rigorous type check. We are considering a limited form of automatic insertion for future versions of C Patrol. However, problems relating to stability are the predominant force in shaping the current system of labeled code [8]. Stability is defined relative to an object, its invariant, and a point in program control flow. An unstable state is a program state where the object invariant is temporarily violated. Unstable states occur frequently during an operation on an object, where the object is being incrementally ....

....Boundary Insertion Internal stability problems result from interrupting a procedure with a check. This problem can be circumvented by performing checks only at function boundaries essentially, adding the checks to the operation s pre and post conditions. This is the approach favored by Eiffel [8] and A [2] where data invariants are enforced as an additional pre and post conditions for operations on objects. Special pre condition exceptions are made for initialization routines. The approach used in Eiffel and A is feasible because the underlying languages support object oriented ....

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B. Meyer. Eiffel the Language. Prentice Hall International, 1992.

....false false false true (5) false false true false X Y A Z Z ae ae X Y q q A H Hj Phi Phi X Y q q A A X Y q q A B X Y q q q q A A A XX z : XX z Fig. 6. Four kinds of equality According to the definitions of Eiffel [16, 17], in contrast, Z is a deep clone of X. Clearly, a complete implementation of deep cloning in Eiffel must detect cyclic references and create corresponding cyclic references in the target object. A similar problem occurs when the object structure contains no (directed) cycles but there are several ....

....of two objects without considering the values of their non reference components. Because structural comparisons can be expensive, it would also be useful to offer also a three valued comparison operation: equal by structure and leaf values; equal by structure only; and unequal by structure. Meyer [16, 305 307] notes that comparison of cyclic structures introduces problems similar to those involved in cloning cyclic structures. In Figure 8, we would like both A = 1 B and C = 1 D to be true, but it is not obvious how to arrive at these results. The attributes f and b are intended to suggest forward ....

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Bertrand Meyer. Eiffel: the Language. Prentice Hall International, 1992.

....of their roots have been scanned. Mutator threads can generate and delete stack frames while they are running, and they are allowed to modify the references of already scanned frames, making rescanning of these frames necessary. Fortunately, in most modern languages like Java [AG98] or Eiffel [Meyer92], it is not possible to modify the contents of stack frames other than the current stack frame. Rescanning is only needed for the frames of those methods that were active since they have last been scanned. A simple solution is to add a flag that indicates the need for rescanning. It is again ....

Bertrand Meyer: Eiffel: The Language, Prentice Hall International (UK) Ltd, Hertforshire, 1992

....decides where the requested information is stored and then accesses that database. Note that from the user s point of view there appears to be only one database. 2. 4 The Active Objects Processor The implementation language for the Active Objects Processor is the object oriented language Eiffel [Meyer, 1992]. We chose an object oriented language as the record structure of the database fitted in well with classes. Database fields are then methods on these classes which access the appropriate database. Also active fields are methods on these classes which access and manipulate the values of non active ....

B. Meyer. Eiffel: The Language. Prentice-Hall International, 1992.

....this tool (metrics definition dictionary, metrics storage, human machine interface) is language independent. Specific implementation language stubs will parse the specification code and determine the base measure function values. The C stub is under construction and we plan to develop an Eiffel [Meyer92] one in the near future. When the tool becomes fully operational, we will proceed to an extensive evaluation of available systems and try to derive and refine the values for the limits mentioned in the design recommendations. The study of correlation between MOOD metrics and quality attributes as ....

Meyer B., Eiffel: The Language, Prentice Hall International, 1992.

....a warehouse of objects which can be pulled into a program and used immediately. The simplest object oriented database, which is nonetheless very useful, just provides object persistence via the assignment of a unique identifier to each object for direct access (as in Eiffel, see Chapter 30 in [Mey92] Another option is to allow queries about object attributes to be issued from within a program (e.g. via SQL strings in [AHS89] here, object caching, indexing and query optimisation need to be carefully controlled to avoid retrieving and interrogating each object in turn. Another style of ....

....the facilities of C available. Since the object oriented paradigm is not enforced, C programs can easily degenerate into bad C programs fast but unstructured, and therefore difficult to maintain. It would be better to employ a purer object oriented language such as Smalltalk[GR85] or Eiffel [Mey92] the latter having the added benefits of static type checking and executable specification code (pre conditions, post conditions and class invariants) The modularity of MMIS 2 means that the implementations of its components with different tools can be compared, while retaining their ....

B. Meyer. Eiffel: The Language. Prentice-Hall International, 1992.

....since each language has its own constructs that allow for implementation of OO mechanisms in more or less detail, a binding for the case studies language (C ) is included ahead 7 . Similar bindings will be proposed for other OO languages in the near future. A validation experiment with Eiffel [Meyer92] is currently under way. This expected, but yet to be proved, language independence will broaden the applicability of this metric set by allowing comparison of heterogeneous system implementations. 3.2 A supporting example To help clarify the metrics determination process, the following C ....

Meyer B., Eiffel: The Language, Prentice Hall International, 1992.

....component of a wide range of modern programming language systems. Examples include very high level languages, such as Icon [1] object oriented languages with late binding times, such as Smalltalk [2] and Self [3] and new languages with traditional compile time type systems such as ML [4] Eiffel [5], Oberon [6] and Modula 3 [7] Garbage collectors have also been implemented for languages that were not originally designed to support garbage collection, such as Modula 2 [8] C [9] and even C [10] Recent implementations tend to use copying collection algorithms instead of mark and sweep ....

Bertrand Meyer. Eiffel: The Language. Prentice Hall International, London, 1992.

....techniques, with several new programming languages being developed to provide the facilities required to implement object oriented systems. One of the most popular is C , a hybrid object oriented language developed from C by Bjarne Stroustrup [24] Another is Eiffel, developed by Bertrand Meyer [19]. The object oriented paradigm provides several new concepts. The most fundamental is the class, which encapsulates data and the methods used to access that data in one package. Similar to the use of ADTs in traditional programming, classes provide a means to enforce data privacy. Classes cannot ....

B. Meyer. Eiffel: The Language. Prentice Hall International, 1992.

....become a handicap in large applications: recent Eiffel compilers generate code that is substantially more efficient than C [8] The language Eiffel was also designed according to principles similar to ours, but Eiffel has additional features that add to its complexity. The official reference is [16] but [17] has a more complete discussion of the rationale for the language. As in Dee and CLU, there is no explicit syntax for pointers. Nevertheless, objects of primitive and expanded classes have value semantics and objects of other classes have reference semantics. Eiffel also provides both ....

....copying may be used to avoid the cost of non local access. There are a few circumstances in which the programmer needs to duplicate an object. Since the assignment operator is not appropriate for rare operations, the language should provide special operations such as Eiffel s Copy and Clone [16] for this purpose. For assignment of immutable objects, the compiler should choose an implementation appropriate to the size of the object. Mutable objects should be assigned by reference. The semantics of the assignment operator should not depend on the form of its operands. Sharing of immutable ....

Bertrand Meyer. Eiffel: the Language. Prentice Hall International, 1992.

....is declarational; it uses the principles of set theory and predicate logic. Appendix A shows parts of a Phone database system (based on [3] as an example of an Object Z specification. We use this example throughout the paper to demonstrate the framework. The OZTEST system uses Eiffel [10] as the implementation language. This does not mean that other object oriented languages could not have been selected; we chose Eiffel because it encourages formalism and it is used in both research and commercial environments. OZTEST consists of several subsystems which will be explained in ....

Bertrand Meyer. Eiffel The Language. Prentice Hall International, Campus 400, Maylands Avenue, Hemel Hempstead, Hertfordshire, HP2 7EL, 1992.

.... have added persistent data types and procedures to Pascal like languages [3] some languages have mechanisms for transmitting arbitrary values between programs and hence long term storage [16] and most object oriented languages have facilities for saving some objects on disk for later retrieval [20]. Persistence is also an important aspect of some programming environments for traditional languages [30] and for maintaining programming environment databases [29] The key difference between these systems and EZ is that most offer persistence as a separate facility and usually restrict it to ....

B. Meyer. Eiffel: The Language. Prentice Hall International, London, 1992.

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Bertrand Meyer. Ei#el: The Language. Prentice Hall International, New York, 1992.

....or without contracts on the development of applications using a library: ease of use, ease of learning, bug avoidance. Section 9 concludes with an assessment of the lessons learned. 2. THE CONTEXT A distinctive design style Applying to reusable libraries the ideas of Design by Contract [6] [7] [9] 11] means equipping each library class with precise specifications, or contracts , governing its interaction with the library s clients. Contracts include the class invariant, stating general consistency conditions to be maintained by every exported routine of the class, and, for every ....

....of current libraries [18] becomes partly unjustified when libraries are built according to this style. The difference is clear, for example, in a comparison of two libraries that cover some of the same ground: EiffelBase, which is based on Design by Contract, and the . NET Collections library [7], which is not. Most non Eiffel libraries, such as the .NET framework s libraries, have indeed been built without consideration to the notion of contract. Three possible explanations come to mind: The library authors do not know about Design by Contract. They know about the concepts, but ....

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Bertrand Meyer: Object-Oriented Software Construction, (1 st edition), Prentice Hall International, 1988.

....additional checking. Only groups, of which the user is a member are allowed. Violating this restriction generates a warning and the assignment is refused. 1 Deferred stands for not fully implemented , abstract . This is one of a set of notions which we borrowed from the nomenclature of Ei el[12]. 3. In fact the previous example already hints at a third application of guarded attributes. The attribute current group is not only documentation but e ectively de nes the permissions of the current user. The effective access rights are always the combination of the user s personal rights and ....

Bertrand Meyer, Eiel: The Language, Prentice Hall International, New York, 1992.

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Bertrand Meyer. Ei#el: The Language. Prentice Hall International, New York, 1992.

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Bertrand Meyer. Ei#el: The Language. Prentice Hall International, New York, 1992. 38, 55, 63, 77, 208

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Bertrand Meyer. EIFFEL The Langage. Prentice Hall International (UK) Ltd, 1992.

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