Engelfriet, J. and Fil`e, G. Simple Multi-Visit Attribute Grammars. J. Comput. System Sci. 24, 3 (June 1982), 283--314.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....in the literature. 5.1 Visit Sequence Evaluators Attribute grammar systems intended for practical programming language analysis generally restrict the class of allowable attribute grammars in order to permit the use of efficient evaluation strategies. Our method is applicable to the ordered [20] class of attribute grammars. These are defined as the attribute grammars for which there exists a family of total orders over the attributes of each phylum such that the attribute instances of each node in every AST can be evaluated in a sequence that respects the ordering for its phylum. As a ....

....which the node belongs. The ordered class is more than adequate for practical purposes, as it contains all AGs evaluable in a fixed number of sweeps or passes as a proper subclass. Unfortunately, testing membership in 50 the ordered class been shown to be NP complete by Engelfriet and Fil e [20], and is regarded as impractical for AGs of realistic size. The difficulty arises in the computation of the required family of total orders on the attributes of each phylum. It is a relatively straightforward polynomial time computation to determine a family of partial orders with the required ....

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Joost Engelfriet and Gilberto Fil'e. Simple multi-visit attribute grammars. Journal of Computer and System Sciences, 24:283--314, 1982.

....from the approximation of attribute dependencies that is required in order to reduce to a polynomial time the complexity of the determination of the attribute evaluation order. If no approximation is used, the problem becomes NP complete. In such a case, the grammar is defined as l ordered AGs [EF82]. In the manual of the Synthesizer Generator TM (SG for short) Gra96] circularities due to the approximation used are called type 3 circularities. In this paper, we follow the SG s terminology. Kastens stated in [Kas80] that type 3 circularities usually do not occur in practical applications ....

....in a root attribute. The scattered information is likely to be described as independent threads of attribute dependencies resulting in many type 3 circularities. The purpose of this paper is to introduce a technique for reducing the problem caused by type 3 circularities in OAGs. As described in [EF82], arranged orderly AGs that is, an AG where approximation is used and extra (virtual) dependencies are added in order to eliminate type 3 circularities is equivalent to l ordered AGs. This fact implies that the problem of eliminating type 3 circularities is NP complete. Thus, instead of ....

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Joost Engelfriet and Gilberto File. Simple multi-visit attribute grammars. Journal of Computer and System Sciences, 24(3):283--314, 1982.

....field) if space is not at stake. An alternative to using a visit sequence interpreter is to code the visit sequences as recursive procedures, as is done in the present version of Fnc 2; the visit stack then becomes implicit. Such an evaluator can be produced only if the AG at hand is l ordered [4]. The characteristics of such an AG is that it is possible to find, for each non terminal, a totally ordered partition of its attributes such that, when augmenting each production dependency graph with the corresponding edges between the attributes of the non terminals in the RHS and LHS of the ....

Engelfriet, J. and Fil' e, G. Simple Multi-Visit Attribute Grammars. J. Comput. System Sci. 243 (June 1982), 283--314.

....grammars (ANCAG ) 8] which is the currently known largest subclass of the well defined grammars with static evaluators. Attribute instances in syntax trees derived from a MAG can be evaluated with visit oriented plans, which are similar to those used in the simple multi visit grammars [3]. Deciding whether a grammar belongs to MAG (and computing the evaluation plans) takes time exponential in the size of the grammar. The size of a grammar consists of five factors: number of terminals, number of nonterminals, number of attributes per symbol, number of productions, and lengths of ....

....G belongs to the class of MAG . According to the definition of MAG , every ADP (q p 1 , p 2 , p k ) in G is acyclic. Therefore, it is possible to produce evaluation orders of attribute occurrences in production q in various situations. We adopt the visit oriented evaluation scheme [3, 6] for MAG . The only difference is that, in simple multi visit attribute grammars (which will be discussed in the last section) there is an evaluation plan for each production. By contrast, in MAG , there is a family of evaluation plans for each production. During evaluation, one plan of the ....

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J. Engelfriet and G. File, Simple multi-visit attribute grammars, J. of Computer and System Sciences 24 pp. 283-314 (1982).

....usually restrict our attention to the well defined attribute grammars (or non circular attribute grammars) which generate syntax trees with no circular dependencies. Kastens identifies the class of l ordered attribute grammars (Kastens, 1978) which is also called the simple multi visit grammars (Engelfriet and File, 1982)) For l ordered grammars, there is a fixed evaluation order of all attributes of all symbols. This evaluation order can be applied to all syntax trees derived from the attribute grammar. Efficient evaluators may be built for l ordered grammars because it is not necessary to find an evaluation ....

....be applied to all syntax trees derived from the attribute grammar. Efficient evaluators may be built for l ordered grammars because it is not necessary to find an evaluation order for each syntax tree. Unfortunately, deciding whether a grammar is l ordered is, in general, an NP complete problem (Engelfriet and File, 1982). A subclass of the l ordered grammars, called OAG, has been identified that allows a polynomial time decision procedure (Kastens, 1980) An l ordered attribute grammar can be arranged orderly (that is, transformed to an ordered grammar) by adding augmented dependencies among attributes. ....

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Engelfriet, J. and G. File (1982) Simple multi-visit attribute grammars. J. of Computer and System Sciences, 24, 283-314.

.... the Follow k sets on a context free grammar, given the First k sets; ffl computing the inherited dependency graphs in an AG, which depend on the synthesized ones; ffl finding the sets of totally ordered partitions in the construction of an l ordered AG equivalent to a given non circular AG [EF 82] this computation also uses the synthesized dependency graphs. Although bottom up and top down GFA problems are not symmetric in the same way as e.g. forward and backward DFA problems, they are solved by similar generic procedures. In some cases, the complexity of a GFA problem can be reduced by ....

Joost Engelfriet & Gilberto Fil`e, "Simple Multi-Visit Attribute Grammars," J. Comput. System Sci. 24 (June 1982), 283--314.

....for more details. In fact, the resolution of class constraints in descriptional composition was the first motivation of this work. In the same way, it is possible to see our coupling evaluator as a generalization of the classical AG transformations for class reduction (e.g. from SNC to l ordered [2]; see also [1] which often work at the specification level. The second advantage is the possibility to construct the coupling evaluators separately while keeping the good properties of descriptional composition, i.e. the fact that the intermediate trees are not constructed. However, only ....

Engelfriet, J. and Fil`e, G. Simple Multi-Visit Attribute Grammars. J. Comput. System Sci. 24, 3 (June 1982), 283--314.

....attributes are specified. With the rapid advance of high performance computer hardware, it is quite natural to consider a parallel evaluator. There are many results concerning parallel evaluation [3, 11, 16, 24] The evaluator for an ordered attribute grammar is a kind of visit oriented evaluator [4]. It is interesting to note that these visit oriented evaluators can be implemented quite easily in a parallel environment. Parallel Virtual Machine (PVM) 9, 19, 20] is a software package that allows a heterogeneous network of parallel and serial computers to appear as a single concurrent ....

J. Engelfriet and G. File, Simple multi-visit attribute grammars, J. of Computer and System Sciences 24 pp. 283-314 (1982).

....trees. During evaluation, the static evaluator simply follows the pre determined scheme. Thus, static evaluators are usually more efficient than dynamic ones. Although static evaluators exist only for certain subclasses of attribute grammars, such as ordered attribute grammars (Kastens, 1980; Engelfriet and File, 1982), it is commonly agreed that these subclasses of grammars are sufficiently large for practical use. We propose in this paper a conditional evaluation scheme for static evaluators that may avoid useless computations. Avoiding useless computations not only speeds up the evaluator, but makes possible ....

.... equations are useful for subexpression ordering (a code generation task in a compiler) Boyland and Graham, 1994) and in computing offsets in a compiler for a series of declarations (Boyland, 1996) Our technique of conditional evaluation is based on the visit oriented evaluation scheme (Engelfriet and File, 1982). There is one evaluation plan for each production rule in the grammar. A plan consists of instructions of the following four kinds: an if then else instruction, evaluation of an attribute instance, a visit to a child node, and a return to the parent node. Our technique generates plans for the ....

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Engelfriet, J. and G. File (1982) Simple multi-visit attribute grammars. J. of Computer and System Sciences, 24, 283-314.

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Engelfriet, J. and Fil`e, G. Simple Multi-Visit Attribute Grammars. J. Comput. System Sci. 24, 3 (June 1982), 283--314.

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J. Engelfriet and G. File , `Simple multi-visit attribute grammars', J. Comput. Syst. Sci., 24, 283-- 314 (1982).

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