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So this article on invariants is both part 1 of the new writing-correct-code series and part 4a of the binary-search series. A few people have complained about the sushi pictures on this blog, so before I plough into the article proper, here is something completely different.In previous articles, I’ve complained about using testing as a crutch (note: about their code. In this mini-series, I want to draw attention to a few concepts that will be patronisingly familiar to most of you who have CS degrees, but which will hopefully be helpful to any avocational programmers hoping to tighten up their code.



At one extreme, some computer-science researchers might try to use these concepts to mathematically prove the correctness of a piece of code — perhaps with the proof being an order of magnitude longer than the code.Through the use of a simple but powerful technique, I was able to write compact, clear code in a short time; and be pretty confident, even before I tested it, that it was correct.That last point is important not as some kind of macho posturing, but because it means that the tests, when I run them, are giving a second distinct line of sight on the problem.There are several candidate representations, none of them greatly better or worse than the others: we could keep track of the highest and lowest array indexes that might hold , or the lowest index and the size of the range; or use asymmetric indexes, where we maintain the index to the base of the current range and the index that points past the end.

For this version of the routine, I’m going to arbitrarily choose to represent the range by two variables, if it’s present.

At the other extreme, a seasoned professional developer probably always has at least a fuzzy and informal notion of an invariant in the back of his head whenever he writes a loop.


Binsearch not updating comments


  • Numpy/binsearch.at master numpy/numpy GitHub profil de paulette60

    paulette60

    Numpy - Numpy main repository. Skip to content. # include " npy_binsearch.h " # define NOT_USED NPY_UNUSED. * Updating only one of the indices based on the.…
  • Writing correct code, part 1 invariants binary search. profil de paulette60

    paulette60

    Daniel, I don’t think there is anything about a recursive solution, as opposed to an iterative one, that demands the loop condition not the invariant.…