Locating type errors in untyped CLP programs

This chapter presents a static diagnosis tool that locates type errors in untyped CLP programs without executing them. The existing prototype is specialised for the programming language CHIP [4.10], but the idea applies to any CLP language. The tool works with approximated specifications which describe types of procedure calls and successes. The specifications are expressed as a certain kind of term grammars. The tool automatically locates at compile time all the errors (with respect to a given specification) in a program. The located erroneous program fragments are (prefixes of) clauses. The tool aids the user in constructing specifications incrementally; often a fragment of the specification is already sufficient to locate an error. The presentation is informal. The focus is on the motivation of this work and on the functionality of the tool. Some related formal aspects are discussed in [4.15, 4.29]. The prototype tool is available from http://www.ida.liu.se/~pawpi/Diagnoser/diagnoser.html.Upprättat; 2000; 20081211 (ysko