. This paper identifies and solves a class of problems that arise in binding time analysis and more generally in partial evaluation of programs: the approximation and loss of static information due to dynamic expressions with static subexpressions. Solving this class of problems yields substantial binding time improvements and thus dramatically better results not only in the case of partial evaluation but also for static analyses of programs --- this last point actually is related to a theoretical result obtained by Nielson. Our work can also be interpreted as providing a solution to the problem of conditionally static data, the dual of partially static data. We point out which changes in the control flow of a source program may improve its static data flow. Unfortunately they require one to iterate earlier phases of partial evaluation. We show how these changes are subsumed by transforming the source program into continuation-passing style (CPS). The transformed programs get specializ...

ion of Typed Contexts Olivier Danvy & Andrzej Filinski DIKU -- Computer Science Department, University of Copenhagen Universitetsparken 1, 2100 Copenhagen , Denmark uucp: danvy@diku.dk & andrzej@diku.dk Abstract This report investigates abstracting control with functions. This is achieved by defining continuations as functions abstracting lexically a delimited context [C[ ]] rather than dynamically an unlimited one C[ ], as it is usually the case. Because their co-domain is distinguished from the final domain of Answers, such continuations can be composed, and this contrasts with the simple exceptions of ML and Lisp and the unlimited first-class continuations of Scheme. Making these functional control abstractions first-class o#ers a new area in programming which this paper explores. The key points obtained here are: a denotational semantics for a simple, call-by-value, strongly typed expression language with higher-order functions and first-class continuations; its congruence with a ...

The IEEE/ANSI standard for Scheme requires implementations to be properly tail recursive. This ensures that portable code can rely upon the space efficiency of continuation-passing style and other idioms. On its face, proper tail recursion concerns the efficiency of procedure calls that occur within a tail context. When examined closely, proper tail recursion also depends upon the fact that garbage collection can be asymptotically more space-efficient than Algol-like stack allocation. Proper tail recursion is not the same as ad hoc tail call optimization in stack-based languages. Proper tail recursion often precludes stack allocation of variables, but yields a well-defined asymptotic space complexity that can be relied upon by portable programs. This paper offers a formal and implementation-independent definition of proper tail recursion for Scheme. It also shows how an entire family of reference implementations can be used to characterize related safe-for-space properties, and proves ...

ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1(212)869-0481, or permissions@acm.org. SIGPLAN ACM Functional Programming i 3 (i 2 ) j 3 (j 2 ) k 3 (k 2 ) if j 3 < 20 3 i 4 (i 2 ) j 4 (j 2 ) k 4 (k 2 ) return j 4 4 i 7 (i 5 , i 6 ) j 7 (j 8 , j 9 ) k 7 (k 8 ,k 9 ) 7 1 i 1 1 j 1 1 k 1 0 2 i 2 (i 7 , i 1 ) j 2 (j 7 , j 1 ) k 2 (k 7 , k 1 ) if k 2 < 100 i 5 (i 3 ) j 5 (j 3 ) k 5 (k 3 ) j 8 i 5 k 8 k 5 +1 5 i 6 (i 3 ) j 6 (j 3 ) k 6 (k 3 ) j 9 k 6 k 9 k 6 +2 6 Yuck! This isn't "the right number of names!" There are too many variables and useless copies. More about this later. Meanwhile, we can view this program as a set of mutually recursive functions, where each function takes arguments i, j, k: functionf 1 () = let i 1 = 1, j 1 = 1, k 1 = 1 in f 2 (i 1 , j 1 , k 1 ) function f 2 (i...

The topic of intermediate languages for optimizing and parallelizing compilers has received much attention lately. In this paper, we argue that any good representation of a program must have two crucial properties: first, it must be a data structure that can be rapidly traversed to determine dependence information, and second this representation must be a program in its own right, with a parallel, local model of execution. In this paper, we illustrate the importance of these points by examining algorithms for a standard optimization --- global constant propagation. We discuss the problems in working with current representations. Then, we propose a novel representation called the dependence flow graph which has each of the properties mentioned above. We show that this representation leads to a simple algorithm, based on abstract interpretation, for solving the constant propagation problem. Our algorithm is simpler than, and as efficient as, the best known algorithms for this problem. An...

Permission is hereby granted to make and distribute verbatim copies of this document without royalty or fee. Permission is granted to quote excerpts from this documented provided the original source is properly cited. ii When separately written programs are composed so that they may cooperate, they may instead destructively interfere in unanticipated ways. These hazards limit the scale and functionality of the software systems we can successfully compose. This dissertation presents a framework for enabling those interactions between components needed for the cooperation we intend, while minimizing the hazards of destructive interference. Great progress on the composition problem has been made within the object paradigm, chiefly in the context of sequential, single-machine programming among benign components. We show how to extend this success to support robust composition of concurrent and potentially malicious components distributed over potentially malicious machines. We present E, a distributed, persistent, secure programming language, and CapDesk, a virus-safe desktop built in E, as embodiments of the techniques we explain.

VLISP has produced a rigorously verified compiler from Scheme to byte codes, and a verified interpreter for the resulting byte codes. The official denotational semantics for Scheme provides the main criterion of correctness. The Wand-Clinger technique was used to prove correctness of the main compiler step. Then a state machine operational semantics is proved to be faithful to the denotational semantics. The remainder of the implementation is verified by a succession of state machine refinement proofs. These include proofs that garbage collection is a sound implementation strategy,

We describe a small set of additions to Scheme to support objectoriented programming, including a form of multiple inheritance. The extensions proposed are in keeping with the spirit of the Scheme language and consequently differ from Lisp-based object systems such as Flavors and the Common Lisp Object System. Our extensions mesh neatly with the underlying Scheme system. We motivate our design with examples, and then describe implementation techniques that yield efficiency comparable to dynamic object-oriented language implementations considered to be high performance. The complete design has an almost-portable implementation, and the core of this design comprises the object system used in T, a dialect of Scheme. The applicative bias of our approach is unusual in object-oriented programming systems. This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is ...

Abstract not found

We define syntactic transformations that convert continuation passing style (CPS) programs into static single assignment form (SSA) and vice versa. Some CPS programs cannot be converted to SSA, but these are not produced by the usual CPS transformation. The CPS!SSA transformation is especially helpful for compiling functional programs. Many optimizations that normally require flow analysis can be performed directly on functional CPS programs by viewing them as SSA programs. We also present a simple program transformation that merges CPS procedures together and by doing so greatly increases the scope of the SSA flow information. This transformation is useful for analyzing loops expressed as recursive procedures. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by per...