J. Gallagher and D. A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151-167, Manchester, UK, 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....Example 5.1. Specializing List Concatenation with Type Checks] Let us consider the following program LConcat for concatenating lists: concat( Ys; Ys) list(Ys) concat( X jXs] Ys; X jZs] list(Xs) list(Ys) list(Zs) concat(Xs ; Ys; Zs) list( list( X jXs] list(Xs) Similarly to [13], we would like to specialize our predicate concat(Xs ; Ys; Zs) w.r.t. the set of triples (Xs ; Ys; Zs) in the Herbrand universe such that the conjunction list(Xs) list(Ys) list(Zs) holds. Thus, we would like to introduce a new predicate, say conc(Xs ; Ys; Zs) and generate a set Eureka of ....

J. P. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In Proceedings of LoPSTr'92, Manchester, U.K., pages 151{

....potential sequences of ever growing characteristic trees. The details of this approach have been elaborated in [40, 35] applied to [34] but the approach can be applied in exactly the same manner to the method of this paper) At first sight, the post processing abstract interpretation phase of [12, 21], detecting useless clauses, might seem like a viable alternative to using pruning constraints and the framework of constrained partial deduction. However, such an approach can not bring back the precomputation that has been lost by an imprecise abstraction operator it might only be able to ....

....to using pruning constraints and the framework of constrained partial deduction. However, such an approach can not bring back the precomputation that has been lost by an imprecise abstraction operator it might only be able to bring back part of the pruning. But, when running the method of [12, 21] e.g. on the residual program P 0 of Example 3.11, no useless clauses are detected. Indeed to be able to do so, one needs an analysis which can do some form of unfolding and in that process preserve characteristic trees in other words exactly the method that we have developed in this paper. ....

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J. Gallagher and D. A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151--167, Manchester, UK, 1992.

....is not the case. For instance, in the standard reverse with accumulating parameter, the accumulator is only copied in the end, but never influences the computation. As illustrated by Example 4. 1 above, this state of affairs will often already be changed when one adds type checking in the style of [22] to even the simplest logic programs. Among larger and more sophisticated programs, cases like the above become more and more frequent, even in the absence of type checking. For instance, in an explicit unification algorithm, one accumulating parameter is the substitution built so far. It heavily ....

J. Gallagher and D. A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151--167, Manchester, UK, 1992.

....5. 1 (Specializing List Concatenation with Type Checks) Let us consider the following program LConcat for concatenating lists: concat( Ys; Ys) list(Ys) concat( X jXs] Ys; X jZs] list(Xs) list(Ys) list(Zs) concat(Xs; Ys; Zs) list( list( X jXs] list(Xs) Similarly to [13], we would like to specialize our predicate concat w.r.t. the predicate input(X) defined by the conjunction: list(Xs) list(Ys) list(Zs) Thus, we would like to introduce a new predicate, say conc(Xs; Ys; Zs) and generate a set Eureka of clauses such that: 23 P [ C 1 : new1(X) F (X; Y ) C 2 ....

J. P. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In Proceedings of LoPSTr'92, Manchester, U.K., pages 151--167. Springer-Verlag, 1993.

....presented in [11] is an adaptation of [1] to the case of Prolog programs with the left to right, depth first control strategy. No theorem proving capabilities are allowed in this method, which as a result, is strictly less powerful than the one described in [1] Finally, de Waal and Gallagher [4, 6] have proposed various techniques to extend partial evaluation. In particular, the notion of partial evaluation with conditions is strongly related to our specialization tree. However, similarly to [3] de Waal and Gallagher s approach makes use of a number of abstract interpretation techniques, ....

J. P. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In Proceedings of LoPSTr'92, Manchester, U.K., pages 151--

....1 Introduction Automatically generated programs often contain redundant parts. For instance, programs produced by standard partial deduction [20] often have useless clauses and redundant structures, see e.g. 7] This has motivated uses of regular approximations to detect useless clauses [9, 6, 5] and the renaming (or filtering) transformation [8, 2] that removes redundant structures. In this paper we are concerned with yet another notion of redundancy which may remain even after these transformations have been applied, viz. redundant arguments. These seem to appear particularly often in ....

J. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T.P. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151--167. Springer Verlag.

....powerful transformation rules [34, 43] and ii) to specialize programs w.r.t. a class of input data satisfying some properties (instead of particular input data) by using either more powerful transformation rules [4, 42] possibly based on theorem proving techniques) or abstract interpretation [24]. 5 Program Transformation and Logic based Software Engineering: Achievements and Future Developments In the previous sections we have presented through some simple examples, some techniques for logic program transformation and we have shown that they may provide valuable tools for logic ....

J. P. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In Proceedings of LoPSTr'92, Manchester, U.K., pages 151--167. Springer--Verlag, 1993.

....at run time and thus, in the absence of downwards closedness, no longer covered) Our paper actually provides a framework within which correctness of [5] could be established for abstract substitutions which are downwards closed. Another, more technical difference is that neither the method of [6, 11] nor the method of [5] preserve the finite failure semantics (i.e. infinite failure might be replaced by finite failure) while our approach, just like ordinary partial deduction, does. Another method that might look like a viable alternative to our approach is the one of [2] situated within the ....

J. Gallagher and D. A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151--167, Manchester, UK, 1992.

....the computation of a general call to a predicate p(x 1 ; xn ) we may get a more precise result for that predicate than by analysing the program bottom up. This was pointed out in [14] and discussed in detail in [7] Examples of query answer transformations can be found in in [14] and [13]. Consider the following permutation program that computes permutations of lists of integers. integer(X) is a built in predicate for which a predefined approximation numeric(X) is derived) permutation(X; Y ) Gammaintlist(X) perm(X; Y ) perm( perm(X; U jV ] Gammadelete(U; ....

....[31] and elsewhere. These applications are well presented by Naish [24] Regular approximation can be combined with the declaration of intended types (stated as regular programs) and program errors detected. The combination of regular approximation with partial evaluation was developed by us in [13]. Deletion of useless clauses, detected by a regular approximation, can greatly improve the results of partial evaluation. This was applied with good results in specialising theorem provers [9] ....

J. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation, pages 151-- 167, Springer-Verlag, 1993.

....rule (usually left to right) is usually assumed for abstract interpretation. 3. 2 Regular Approximations The safe approximations used in this paper are Regular Unary Logic (RUL) programs, defined in [29] For any program P , we construct an RUL program that is a safe approximation of P [8]. This can then be used to detect useless clauses, since finite failure of definite goals is decidable in an RUL program. A regular unary clause is of the form p(f(x 1 ; x n ) t 1 (x 1 ) t n (x n ) where x 1 ; x n are distinct variables. An RUL program is a set of ....

....a common instance. It is decidable whether a given goal succeeds in an RUL program. A goal does not succeed if and only if it fails finitely. A detailed description of a method for computing a regular approximation of a given normal program can be found in [7] and the method is also summarised in [8]. Briefly, the method is based on abstract interpretation of the standard fixpoint semantics of a definite program P , given by its T P operator. An abstract version of the T P operator is defined, more specifically, a monotonic operator that maps one RUL program to another. Its least fixed point ....

J. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation, Workshops in Computing, pages 151--167. Springer-Verlag, 1993.

....to that computation. We quote the frameworks described in [25] and [2] as examples of appropriate methods. Space does not permit a detailed description of the analysis method that we used for the results reported in this paper, but we outline the main ideas. Detailed descriptions can be found in [9] and [10] The central notion is that of a safe approximation of a program. Definition 5.1 safe approximation Let P and P 0 be normal programs. Then P 0 is a safe approximation of P if for all definite goals G, ffl if P 0 [f Gg has a finitely failed SLDNF tree then P[f Gg has no ....

....approximations in which finite failure is decidable. 5. 1 Regular Safe Approximations In the work reported here we used Regular Unary Logic (RUL) programs, defined in [26] For any program P , we construct, using an abstraction of the T P operator, an RUL program that is a safe approximation of P [9]. This can then be used to detect useless clauses, since finite failure of definite goals is decidable in an RUL program. An RUL approximation algorithm has been implemented in Prolog and has been successfully run on large programs. In the worst case such algorithms, like other computations ....

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J. Gallagher and D.A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation, pages 151--167, Springer-Verlag, 1993.

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J. Gallagher and D. A. de Waal. Deletion of redundant unary type predicates from logic programs. In K.-K. Lau and T. Clement, editors, Logic Program Synthesis and Transformation. Proceedings of LOPSTR'92, pages 151-167, Manchester, UK, 1992.

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