Back in another era, when I worked for UbiSoft, my then-boss Alain, started a wonderful initiative – the Technical Meeting. Every Friday afternoon, one of us should present a technical argument to the whole team. A good number of Technical Meetings were held, but when the project entered some frantic period. I have fond memories of these meetings.
So I was very happy when I heard that a similar initiative was going to happen at Schindler – the biweekly Technical Session. The idea is very similar – every two weeks one of the colleagues volunteers to make a short technical presentation and give it to the team. Topics are diverse, mainly related to C++. The goal is to have compact presentations limited to 10-15 minutes, ideally including some hands-on parts.
I volunteer for the second topic, which in turn I’ll present here.
A few years ago I attended a talk at a Lambda World Conference about Lambda Calculus. Although not an eye-opener (in fact that level of abstraction is rarely needed, nor advisable, in everyday programming), it was thought-provoking. By wisely crafting mathematical functions you could describe algorithms, fully equivalent to the good old recipe-like imperative programming code.
The point is that those lambda functions are really twisted.
Reading some anecdotes about Alonzo Church it is immediately clear he was quite a guy. And devising lambda calculus required quite a mind.
Since lambda calculus is just functions, no statement, it came to my mind I could use it to devise a solution to my “if-less” programming quiz.
The solution I prepared was too complex to be explained in my previous post, so I decided to write this post.
The combo – backward-compatibility latch and committee-driven approval/refusal of proposals, make the language evolution spin around. Missing or late additions to the language are sitting ducks, and the lack of networking in the standard library, for a language that is 40, is enough to tell how poorly the evolution of the language is handled.
In my last post, I described the first Schindler Milan office weekly riddle. It has been a big success, and it had a brilliant winning solution (one of mine 🙂 ). A simple problem, implementing increment by one without using addition, yet open enough to trigger a good number of solutions.
As the winner, it was my duty to invent the next riddle. A really daunting task if I wanted to live up to the expectations. Honestly, I didn’t invent anything, I just squeeze the web looking for a good programming riddle in the drops.
Do you remember the good old point-and-click adventures? They provided plenty of puzzles and riddles with a compelling narrative. I loved them, possibly because I love riddles, puzzles, and this sort of challenge. So I was super excited when my employer supported the initiative of a Coding-Riddle-of-the-Week contest. This is the second issue and I’m going to present it here.
Produce a program which increments an integer variable by a value of 1 without using sum or increment operators.
You are pretty free to choose whatever integer size and type you prefer (I would say, but bool), and whatever language you want. I stuck with C++ because it was quicker, but most of my solutions can be easily ported to other languages.
So, before continuing be sure to give some thought to this riddle to not spoil the fun.
Managing errors and failures in every programming language is usually a pain. Most programming book authors just show the happy path scenario, sometimes noting down that error handling has to be done, but it has been left out for improving simplicity (and readability).
C++ offers the exception mechanism, which is a clever way to leave the happy path in sight and hide the troubles under the carpet. Even before questioning if this is a good idea or not, C++ abstraction is so delicate that you need to take particular care in making your code exception-safe. Meaning that in case of exception your program does not leak resources and leaves everything in a useful state so that the exception can indeed be recovered from.
“He Who Laughs Last Is At 300 Baud”, is possibly a long-forgotten joke, but sometimes C++ standard is like using a 300 baud modem, discovering “innovations” tens of years after other less committee-centric languages discover and apply them.
Let’s take the std::optional which tries to mimic the Option monad available in other languages. Since 1990 there has been a resurgence of functional programming languages in the mainstream – Haskell (1990), and Scala (2004) just to name two that have Option since their first version.
In theory, practice and theory are the same, in practice they are not. So, after having read how brilliant and smart smart-types are, it is now time to have a closer look at the compiler and figure out what C++ can offer.
Simple things first, if you need a type with a bunch of possible values, don’t use int & #defines, don’t use bool either (please), use enum, or, even better enum class.
Now that we’ve done with the trivialities, let’s proceed to something more challenging – numeric types. Ideally, we want some template code that wraps the numeric type and saves us the boredom of writing all the usual +, -, *, /, ==, !=, <… operators, while letting us define the rules of the existence of the represented type.