Tag: functional programming

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

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?

“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++)

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

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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Scala Job Interview – FP questions

Welcome to the third installment of the Scala Job Interview Questions series. This time I’ll try to answer functional programming questions, likely my score will be a bit less than the first two editions (General Questions and Language Questions) because I like Functional Programming, but I’m still a traditional programmer (imperial?) who studied Algebra at high school and uni and then consider Algebra as useful (for programmers) as a doorstop in a tent.

Young and foolish I was, but who could imagine, back then that to run the dance of the bits I would ever need monoids?

Let’s not waste other time in void introduction, and start with the questions and my answers.

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Scala Job Interview Answers

Idling over Twitter I came across a post on Signify blog about a list of Scala Job Interview Questions. The post in fact referenced a GitHub repository. Now the post came with a pointer to ready-made answers, but I decided to take the exercise and try to reply myself. The intent was both to check my knowledge and to learn something new since I’m no Scala guru.

The post contained many questions, grouped by topic. So I prefer to split my answers along several posts to keep them short and manageable.

Let’s start with general questions.

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Is C++ Ready for Functional Programming? – Wrap Up

Wrap Up

Recently I had the questionable pleasure of watching “Cosmic Sin” courtesy of Netflix. The movie is a sci-fi show starring Bruce Willis. I was lured into wasting my time on it, by the trailer promising a space-operish feat and I took the presence of such a star playing in the movie for a warranty on quality. I couldn’t be farther from the truth.

The movie plays out confusingly, lacking a coherent script and motivated actors, pushing the watcher into an undefined state (not UB luckily). The helpless watcher, astonished by how bad a film could be, hopes until the very last for something interesting and entertaining to happen until the mixed relief-disbelief emotion of closing titles puts an end to the suffering.

When thinking about C++ and functional programming I have some of the feelings I had watching the movie. Before being persecuted by my friends from the C++ community I have to make clear that C++ is not that bad, although there are some similarities.

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Is C++ Ready for Functional Programming? – Types

Types

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Although functional programming can be done in a dynamically typed language (Lisp, the functional programming language forerunner, had no types), strong static type adds a very natural complement to functional programming.

From a mathematical point of view, a function sets a relationship between the set defined by the function argument (domain in math speaking) and the corresponding results (co-domain). Algebra studies exactly these relationships and may help the programmer in proving certain properties of the functions composing the programs.

Algebraic Data Types (ADT) are aggregated types in the algebra context. Two ADTs are of particular interest – sum types and product types. With sum and product referring to the resulting number of possible values (i.e. cardinality of sets).

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Is C++ Ready for Functional Programming? – Standard Library

Time to take a closer look to the standard library from the functional programming point of view.

In the first installment of this series, I stated that using a library to implement functional programming structures would not be an ideal solution, but as C language pioneered in the 70s, part of the language finds its proper location in a library.

C++ standard library has grown disorderly oversize during the years, so let’s have a look at what kind of support is available for those that want to use C++ with the functional paradigm.

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