Programming by Contract vs. Defensive Programming

179 Pages·2012·0.83 MB·English

Department of Computer Science
Roger Andersson Patrick Jungner
Programming by Contract vs. Defensive
Programming: A Comparison of Run-time
Performance and Complexity
Master’s Thesis
2003:03

Programming by Contract vs. Defensive
Programming: A Comparison of Run-time
Performance and Complexity
Roger Andersson Patrick Jungner
(cid:13)c 2003 The authors and Karlstad University

This thesis is submitted in partial ful(cid:12)llment of the requirements
for the Masters degree in Computer Science. All material in this
thesis which is not my own work has been identi(cid:12)ed and no mate-
rial is included for which a degree has previously been conferred.
Roger Andersson
Patrick Jungner
Approved, June 17, 2003
Advisor: Donald F. Ross
Examiner: Anna Brunnstro(cid:127)m
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Abstract
Wehaveusedtwoknownprinciplesintodayssoftwaredevelopmentscene,namely: contract
basedprogramming, advocatedbyBertrandMeyerasthecreatorofDesignbyContractTM,
and Defensive Programming, described by Barbara Liskov et al. We compared two com-
pilers implemented by using Programming by Contract, a contract based programming
principle, and Defensive Programming. The size of each compiler is in the region of 4500
lines of code. The comparison is made by performing measurements on the code.
After completion of the experiment we found no discernible di(cid:11)erence in the size or
complexity of the source code of the two compilers. We did however come to the con-
clusion that contract based programming should not be used without automated support.
Neither of the two principles could be said to be part of the solution for creating reliable
software systems unless the programmers have the discipline to follow the ideas behind the
principles.
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Acknowledgements
We would like to thank our supervisor Donald F. Ross for all his help and guidance during
the project.
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