A slicing-based approach for locating type errors

The effectiveness of a type checking tool strongly depends on the accuracy of the positional information that is associated with type errors. We present an approach where the location associated with an error message e is defined as a slice P_e of the program P being type checked. We show that this approach yields highly accurate positional information: P_e is a program that contains precisely those program constructs in P that caused error e. Semantically, we have the interesting property that type checking P_e is guaranteed to produce the same error e. Our approach is completely language-independent, and has been implemented for a significant subset of Pascal

A slicing-based approach for locating type errors

The effectiveness of a type checking tool strongly depends on the accuracy of the positional information that is associated with type errors. We present an approach where the location associated with an error message e is defined as a slice P_e of the program P being type checked. We show that this approach yields highly accurate positional information: P_e is a program that contains precisely those program constructs in P that caused error e. Semantically, we have the interesting property that type checking P_e is guaranteed to produce the same error e. Our approach is completely language-independent, and has been implemented for a significant subset of Pascal

An extensible language for the generation of parallel data manipulation andcontrol packages

The design and implementation of the language fSDL (full Structure Definition Language) is discussed. In fSDL, complex user-defined data types such as lists, tables, trees, and graphs can be constructed from a tiny set of primitives. Beyond mere structure definitions (also offered by previously existing tools) high-level functionality on these data types can be specified. In the COMPARE (ESPRIT) project, the C code generated from an fSDL specification will be used by compiler-components running in parallel on a common data pool. fSDL is first translated into a sublanguage, flat fSDL, from which the actual C code is produced. Flat fSDL is a convenient interface for cooperation with other compiler generation tools. There is a formal relation between the input fSDL and the resulting flat form

Animators and error reporters for generated programming environments

We study animators and error reporters for generated programming environments. An error reporter is a tool for indicating the exact position of a type-error in the source text. An animator visualizes program execution; typically, it highlights the statement that is currently executing. Applications of both tools are mainly to be found in the areas of debugging and tutoring. Instead of explicitly extending language specifications with these facilities, we claim that error reporters and animators can be generated from existing specifications for type-checkers and interpreters with little effort; to this end, a simple pattern-matching mechanism is used in conjunction with origin tracking, a generic tracing technique. In this paper, we discuss our claim, and at the same time investigate the limitations and deficiencies of origin tracking. Our techniques are illustrated using an example language named CLaX, a Pascal relative. The full specifications of the CLaX syntax, type-checker and interpreter are included in appendices

Towards a complete transformational toolkit for compilers

PIM is an equational logic designed to function as a ``transformational toolkit'' for compilers and other programming tools that analyze and manipulate imperative languages.It has been applied to such problems as program slicing, symbolic evaluation, conditional constant propagation, and dependence analysis.PIM consists of the untyped lambda calculus extended with an algebraic data type that characterizes the behavior of lazy stores and generalized conditionals.A graph form of PIM terms is by design closely related to several intermediate representations commonly used in optimizing compilers. In this paper, we show that PIM's core algebraic component, PIM$_t$, possesses a complete equational axiomatization (under the assumption of certain reasonable restrictions on term formation). This has the practical consequence of guaranteeing that every semantics-preserving transformation on a program representable in PIM$_t$ can be derived by application of PIM$_t$ rules. We systematically derive the complete PIM$_t$ logic as the culmination of a sequence of increasingly powerful equational systems starting from a straightforward ``interpreter'' for closed PIM$_t$ terms. This work is an intermediate step in a larger program to develop a set of well-founded tools for manipulation of imperative programs by compilers and other systems that perform program analysis

A complete transformational toolkit for compilers

In an earlier paper, one of the present authors presented a preliminary account of an equational logic called PIM. PIM is intended to function as a 'transformational toolkit' to be used by compilers and analysis tools for imperative languages, and has been applied to such problems as program slicing, symbolic evaluation, conditional constant propagation, and dependence analysis. PIM consists of the untyped lambda calculus extended with an algebraic rewriting system that characterizes the behavior of lazy stores and generalized conditionals. A major question left open in the earlier paper was whether there existed a complete equational axiomatization of PIM's semantics. In this paper, we answer this question in the affirmative for PIM's core algebraic component, PIMt, under the assumption of certain reasonable restrictions on term formation. We systematically derive the complete PIM logic as the culmination of a sequence of increasingly powerful equational systems starting from a straightforward 'interpreter' for closed PIM terms