Using the Dafny Verification System in An Introduction To Algorithms Class

Algorithm students often have difficulty understanding and using problem specifications and algorithm outlines. During the first three weeks of an algorithms class, the author used Dafny to address this. Dafny is a programming language and verification system developed at Microsoft Research. A Dafny program requires explicit preconditions, post conditions, loop invariants, and loop termination counters. In return, it uses a theorem prover to mechanically prove or question the correctness of method outlines and implementations. The preliminary results of this trial suggest that when students work with Dafny, they better understand and appreciate the importance of preconditions, post conditions, invariance and loop termination.