If I’m not pure, at least my functions are

by






It is often suggested that the programming language should support specifying that a routine is pure; many people have indeed proposed the addition of a keyword such as pure to Eiffel. One of the reasons this is not — in my opinion — such a great idea is that purity is just a special case of the more general problem of framing: specifying and verifying what a routine does not change. If we can specify an arbitrary frame property, then we can, as a special case covered by the general mechanism, specify that a routine changes nothing. The language solution is simple: no routine may change the value of a query other than those specified in its postcondition




Agile methods: the good, the bad and the ugly

by






Agile methods are wonderful. They’ll give you software in no time at all, turn your customers and users into friends, catch bugs before they catch you, change the world, and boost your love life.







Assessing concurrency models

by






In a recent experiment with students we wanted to know how the SCOOP concurrency model compares to Java Threads in terms of ease of learning, program readability and correctness. Our group, however, is heavily involved with SCOOP. How did we address the risk of bias, and other parts of the “Professor Smith Syndrome”? What are our results, and can you believe them?







The Professor Smith syndrome: Part 1 – a quiz

by






[As a reminder, this blog is now on a regular schedule, appearing every Monday. Sometimes in mid-week there will be a lighter piece or, as here, a preparation for the following Monday’s entry.] Consider the following hypothetical report in experimental software engineering (see earlier posts: [1], [2]): Professor Smith has developed a new programming technique, … Read more




In praise of Knuth and Liskov

by






Youth has its advantages; perhaps the most striking is that we can, in our own lifetime, meet in person some of the very founders of our discipline. No living physicist has seen Newton; no chemist has heard Lavoisier. For us, it works. Today, Ladies and Gentlemen, we have the honor of introducing two of the undisputed pioneers of informatics.







Publish no loop without its invariant

by






There may be no more blatant example of the disconnect between the software engineering community and the practice of programming than the lack of widespread recognition for the fundamental role of loop invariants.