Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....be exploited to design a language as efficient as C but with significantly more uniformity and flexibility. 2 Language Design Research The Cecil language design began in 1991 as an attempt to combine the advantages of Self [Ungar Smith 87] CLOS [Bobrow et al. 88, Steele 90] and Trellis [Schaffert et al. 85, Schaffert et al. 86] a simple, uniform language based on dynamic dispatching, the use of multiple dispatching, and a sound static type system. The central design principle followed 2 in Cecil was to base the language on a flexible dynamic dispatching mechanism, and then to use this mechanism ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November 1985.

....with ambiguities according to C s rules produce IL code. Vortex s semantics are sufficient to handle the inheritance rules for single inheritance languages such as Java, Modula 3, and Smalltalk [Goldberg Robson 83] and to handle multiple inheritance languages such as Cecil, C , and Trellis [Schaffert et al. 85] However, some languages use other rules for method lookup (such as CLOS, which uses a left to right ordering of parents for resolving ambiguities [Bobrow et al. 88] and compiling such languages would require adding back end support for more generally computing the required partial order from ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical Report DEC-TR-372, Digital Equipment Corporation, November 1985.

....Leavens 94] Cecil is unusual in combining a pure, classless object model, multiple dispatching (multi methods) modules, and mixed static and dynamic type checking. Cecil was inspired initially by Self [Ungar Smith 87, Hlzle et al. 91a] CLOS [Bobrow et al. 88, Gabriel et al. 91] and Trellis [Schaffert et al. 85, Schaffert et al. 86] The current version of Cecil extends the earlier version [Chambers 93a] with predicate objects, modules, and efficient typechecking algorithms. 1.1 Design Goals and Major Features Cecil s design results from several goals: Maximize the programmer s ability to develop ....

....on function arguments, but all overloading is resolved at compile time based on the static types of the arguments (and results, in the case of Ada) rather than on their dynamic types as would be required for true multiple dispatching. Trellis supports an expressive, safe static type system [Schaffert et al. 85, Schaffert et al. 86] Cecil s parameterized type system includes features not present in Trellis, such as implicitly bound type variables and uniform treatment of constrained type variables. Trellis restricts the inheritance hierarchy to conform to the subtype hierarchy; it only supports ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

....local objects. However, the language also provides constructs to force the creation or execution of an object to take place at a specified node. Persistence is usually provided in languages for databases (FAD [4] Galileo [2] and distributed systems (Emerald [6] Other languages (Trellis Owl [25], Eiffel [20] provide persistent objects as an add on feature. Objects in Guide are potentially persistent. However, only objects which are reachable from a persistent root are made persistent by the run time system; other objects are subject to garbage collection. It would be conceptually ....

C. Schaffert, T. Cooper and W. Carrie, Trellis Object-Based Environment, Language Reference Manual, DE-TR-372, november, (1985).

....the restriction in most object oriented languages that instance variables cannot be overridden limits the reusability of code to only those abstractions which wish to use the same representation. Other object oriented languages such as SELF [Ungar Smith 87, H lzle et al. 91a] and Trellis [Schaffert et al. 85, Schaffert et al. 86] have demonstrated the advantages of accessing instance variables solely through special get and set accessor methods. In the traditional generic function oriented view of multi methods, however, accessing instance variables solely through multi methods appears problematic. ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

....virtual. For the benchmark programs discussed in Section 5, slightly more than half of the message sends that were statically bound through class hierarchy analysis could not have been made non virtual in C (i.e. had more than a single definition of the routine) In a similar vein, Trellis [Schaffert et al. 85, Schaffert et al. 86] allows a class to be declared with the no subtypes annotation, Dylan [Dyl92] allows a class to be sealed (indicating that it will have no subclasses other than those statically visible in the same compilation unit) and Java provides the most general mechanism by allowing ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical Report DEC-TR-372, Digital Equipment Corporation, November 1985.

....virtual. For the benchmark programs discussed in section 3, slightly more than half of the message sends that were statically bound through class hierarchy analysis could not have been made non virtual in C (i.e. had more than a single definition of the routine) In a similar vein, Trellis [Schaffert et al. 85, Schaffert et al. 86] allows a class to be declared with the no subtypes annotation and Dylan [dyl92] allows a class to be sealed, both of which inform the compiler that no subclasses exist. These annotations allow the compiler to treat the class as a leaf class and compile all messages sent to ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical Report DEC-TR-372, Digital Equipment Corporation, November 1985.

....to be allowed to a program. Java has final methods, which are somewhat more flexible than virtual functions, but still suffer from the same problems discussed above. Another common language feature is the ability to declare a class as a leaf class, exemplified by Trellis s no subtypes annotation [Schaffert et al. 85, Schaffert et al. 86] Dylan s seal annotation [Dyl92] and Java s final annotation when applied to a class declaration [Gosling et al. 96] All of these are ways to inform the compiler that there will be no subclasses of the class, which can optimization of messages sent to an isntance of the ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical Report DEC-TR-372, Digital Equipment Corporation, November 1985.

....This presents a problem when writing a program to browse over them. In general, one cannot write a static program to anticipate all of the types that may occur without resorting to some magic or a second level of interpretation. Object oriented programming languages [1,2] with a few exceptions [3] avoid this problem by resorting to a combination of conventions and dynamic typing. For example, one solution to this problem would be for every instance of a class to have a print method. This is not a safe solution to the problem since a print method may be overwritten by a method which ....

Schaffert C.,Cooper T. and Wilpolt C. Trellis Object Based Environment. DEC TR-372, Digital Eastern Research Lab (1985).

....virtual. For the benchmark programs discussed in Section 3, slightly more than half of the message sends that were statically bound through class hierarchy analysis could not have been made non virtual in C (i.e. had more than a single definition of the routine) In a similar vein, Trellis [Schaffert et al. 85, Schaffert et al. 86] allows a class to be declared with the no subtypes annotation and Dylan [Dyl92] allows a class to be sealed, both of which inform the compiler that no subclasses exist. These annotations allow the compiler to treat the class as a leaf class and compile all messages sent to ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical Report DEC-TR-372, Digital Equipment Corporation, November 1985.

....Leavens 94] Cecil is unusual in combining a pure, classless object model, multiple dispatching (multi methods) modules, and mixed static and dynamic type checking. Cecil was inspired initially by Self [Ungar Smith 87, H lzle et al. 91a] CLOS [Bobrow et al. 88, Gabriel et al. 91] and Trellis [Schaffert et al. 85, Schaffert et al. 86] The current version of Cecil extends the earlier version [Chambers 93a] with predicate objects, modules, and efficient typechecking algorithms. 1.1 Design Goals and Major Features Cecil s design results from several goals: Maximize the programmer s ability to develop ....

....on function arguments, but all overloading is resolved at compile time based on the static types of the arguments (and results, in the case of Ada) rather than on their dynamic types as would be required for true multiple dispatching. Trellis supports an expressive, safe static type system [Schaffert et al. 85, Schaffert et al. 86] Cecil s parameterized type system includes features not present in Trellis, such as implicitly bound type variables and uniform treatment of constrained type variables. Trellis restricts the inheritance hierarchy to conform to the subtype hierarchy; it only supports ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

....presents a problem when writing a program to browse over them. In general, one cannot write a static program to anticipate all of the types that may occur without resorting to some magic or a second level of interpretation. Object oriented programming languages [gold83,bob81] with a few exceptions [sch85] avoid this problem by resorting to a combination of conventions and dynamic typing. For example, one solution to this problem would be for every instance of a class to have a print method. This is not a safe solution to the problem since a print method may be overwritten by a method which ....

Schaffert C.,Cooper T. and Wilpolt C. Trellis Object Based Environment. DEC TR-372, Digital Eastern Research Lab (1985).

....Cecil is unusual in combining a pure, classless (prototype based) object model, multiple dispatching (multi methods) and mixed static and dynamic type checking. Cecil was inspired primarily by SELF [Ungar Smith 87, H lzle et al. 91a] CLOS [Bobrow et al. 88, Gabriel et al. 91] and Trellis [Schaffert et al. 85, Schaffert et al. 86] 1.1 Design Goals and Major Features Cecil s design results from several goals: Maximize the programmer s ability to develop software quickly and to reuse and modify existing software easily. In response to this goal, Cecil is based on a pure object model: all data are ....

....al. 90] support static overloading on function arguments, but all overloading is resolved at compile time based on the static types of the arguments rather than on their dynamic types as would be required for true multiple dispatching. Trellis supports an expressive, safe static type system [Schaffert et al. 85, Schaffert et al. 86] Cecil s parameterized type system includes features not present in Trellis, such as implicitly bound type variables and uniform treatment of constrained type variables. Trellis restricts the inheritance hierarchy to conform to the subtype hierarchy; it only supports ....

Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

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Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

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Craig Schaffert, Topher Cooper, and Carrie Wilpolt. Trellis Object-Based Environment, Language Reference Manual. Technical report DEC-TR-372, November, 1985.

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