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Lambda Headache for Mere Mortals

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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.

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Sign of the times

Nothing lasts forever, but Cobol, Fortran, and C++

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If you have kept up to date with the latest developments of C++, for sure you have noticed how convoluted and byzantine constructs and semantics have become.

The original idea of a C with Classes at the root of language is long lost and the fabled smaller and cleaner language hidden inside C++ is ever more difficult to spot and use.

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.

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What if “if” would go missing?

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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.

Eventually, I decided to go for determining the lowest of two numbers… using if-less programming. After all, if statement can be tricky and someone already pointed out that if statement should be considered harmful in the same way the infamous goto is.

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Mom! My plus key is broken!

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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.

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Dealing with Errors in C++ Using a Lightweight Monadic Approach

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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.

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What’s wrong with you, std::optional?

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“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.

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As Smart as a Smart Type – Practice (C++)

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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.

After my last post, I found that Smart Types are also known as Refined (or refinement) Types. And here is a notable implementation for Scala.

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.

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As Smart as a Smart Type – Theory

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Recently I listened to a “Happy Path Programming” podcast episode about Smart Types. And that inspired me for this double post. The first part (this one) is about what a smart type is and why you should employ smart types in your code. The second part (yet to come, hopefully soon) is about the troublesome way I implemented an arithmetic smart type template in C++.

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