Computing

In education teachers strive to demystify tough concepts by coming up with succinct and minimalistic examples and case studies. Frequently, despite investing great effort, the underlying mechanisms remain surrounded by mystic clouds just because the substrate over which things are exposed is at an overly high abstraction level. This is the case with recursion when illustrated via mainstream programming languages. In this blog, I would like to share a different approach of explaining processes under the hood using a low conceptual programming layer, namely machine language. It is remarkable how students easily comprehend recursion at this level without being dragged into thinking what is really going on in the background in programs written in Java, C#, Python, or any other modern programming language. Problem Description For teachers the booksite accompanying the book Computer Science: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne is an excellent source of educati...

We strive to craft maintainable software systems, since evolution of large systems is their most important and longest lifecycle phase. Various software development paradigms, like functional and object-oriented programming, contain wealth of approaches how to attain the previous objective. One of them is the creation and usage of custom data types. This blog peeks into the power of strongly typed programming languages and shows via a simple case study how to devise a flexible application by adorning it with custom data types. For this purpose I will use Java, but the general ideas are language agnostic. Problem Description For teachers the booksite  accompanying the book Computer Science: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne is an excellent source of educational materials. I will provide here solutions to some exercises that are not published in this book nor on the booksite, at the time of writing this document. The main task is to write a client ...

A command-line processor, as its name implies, is a software appliance intended to be executed from a command-line in pipelined fashion. Most operating systems are equipped with bunch of utilities that can be ingeniously combined to create powerful mini programs for transforming data. We will focus our attention here on jq specialized to mangle JSON data similarly how sed crunches textual content. You can easily start using it by issuing brew install jq on macOS (or download it for other operating systems). Nonetheless, even without placing anything on your machine, there is also a nice playground for trying out things online. The following example illustrates what sort of actions could be crafted into a unified instruction, i.e., mini program that may be reused as a whole: > echo "A test string." | jq -R "ascii_upcase | gsub(\"STRING\"; \"CONTENT\")" "A TEST CONTENT." The input is piped into jq as an ordinary string (this is hi...

In all creative disciplines fundamental ideas reoccur in different shapes. This cannot be truer in computer science and software engineering. Advances in technology even enables old ideas to appear as pure novelties. In this article we will focus on an intellectual toolbox associated with morphing existing ideas, concepts, and technique to fit new scenarios. This is tightly connected with generalization and pattern matching, which are both prominent ingredients in achieving success in professional practice and various competitive activities. The latter is examined in more detail in my article about competitive software engineering . To make the point clear let us use a concrete example from Petlja , a website maintained by the Serbian Mathematical Society, which also organizes official competitions in mathematics and programming. The problem we will use is called Mingo . Below is its description translated to English. Problem Description Now, after completing the competition, Miroslav ...

JSON API provides a systematic method of specifying Level 3 REST APIs in JSON. It has a registered hypermedia type of application/vnd.api+json issued by the Internet Assigned Numbers Authority (IANA). The next list briefly enrolls the most salient features and benefits of JSON API (see my book Creating Maintainable APIs for more information): It is a hypermedia-driven conventional interface : This is a fundamental difference between JSON API and other pure message formats. The JSON API, besides establishing a shared convention regarding message formats, also encompasses rules for how to interact with services (it specifies an assumed API). For example, JSON API contains instructions on how services should fetch, create, update, and delete resources, specify pagination, pass query parameters, and so on. This trait of JSON API is tightly related to the concept of openness in distributed systems. An open distributed system mandates certain rules regarding how services should be implem...