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Stephan Schweitzer

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

3 papers

1 author row

LPAR Conference 2005 Conference Paper

Reasoning About Incompletely Defined Programs

Christoph Walther
Stephan Schweitzer

Abstract We consider automated reasoning about recursive partial functions with decidable domain, i. e. functions computed by incompletely defined but terminating functional programs. Incomplete definitions provide an elegant and easy way to write and to reason about programs which may halt with a run time error by throwing an exception or printing an error message, e. g. when attempting to divide by zero. We investigate the semantics of incompletely defined programs, define an interpreter for those programs and discuss the termination of incompletely defined procedures. We then analyze which problems need to be solved if a theorem prover designed for verification of completely defined programs is modified to work for incompletely defined programs as well. We also discuss how to reason about stuck computations which arise when calling incompletely defined procedures with invalid arguments. Our method of automated reasoning about incompletely defined programs has been implemented in the verification tool \(\surd{\rm eriFun}\). We conclude by discussing experiences obtained in several case studies with this implementation and also compare and relate our proposal to other work.

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LPAR Conference 2004 Conference Paper

Automated Termination Analysis for Incompletely Defined Programs

Christoph Walther
Stephan Schweitzer

Abstract Incompletely defined programs provide an elegant and easy way to write and to reason about programs which may halt with a run time error by throwing an exception or printing an error message, e. g. when attempting to divide by zero. Due to the presence of stuck computations, which arise when calling incompletely defined procedures with invalid arguments, we cannot use the method of argument bounded algorithms for proving termination by machine. We analyze the problem and present a solution to improve this termination analysis method so that it works for incompletely defined programs as well. Our technique of proving the termination of incompletely defined programs maintains performance as well as simplicity of the original method and proved successful by an implementation in the verification tool \(\surd\) eriFun.

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LPAR Conference 2003 Conference Paper

A Machine-Verified Code Generator

Christoph Walther
Stephan Schweitzer

We consider the machine-supported verification of a code generator computing machine code from WHILE -programs, i. e. abstract syntax trees which may be obtained by a parser from programs of an imperative programming language. We motivate the representation of states developed for the verification, which is crucial for success, as the interpretation of tree-structured WHILE -programs differs significantly in its operation from the interpretation of the linear machine code. This work has been developed for a course to demonstrate to the students the support gained by computer-aided verification in a central subject of computer science, boiled down to the classroom-level. We report about the insights obtained into the properties of machine code as well as the challenges and efforts encountered when verifying the correctness of the code generator. We also illustrate the performance of the \(\checkmark\) eriFun system that was used for this work.

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