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The video of New Tools for a More Functional C++

My previous talk on New Tools for a More Functional C++ ran into some audio issue during the meetup. I did not upload the video back then because it had no audio what-so-ever. I finally got around to record the audio track for the talk and I mixed it with the video. So here is the final video. Have fun with FP in C++!

If you don't have 35 minutes, checkout the partial video transcripts below.

Functional Programming Tools in C++ from Sumant Tambe on Vimeo.

Video Transcripts

We’re going to talk about functional [programming] tools in C++ and what new capabilities exist in modern C++. 

I'm reviewing Functional Programming in C++ book by Manning---a good book for C++ programmers to acquire beginner to intermediate level knowledge of FP in C++.

Sum types and (pseudo) pattern matching in C++

Modeling a game of Tennis using std::variant

std::visit spews blood when you miss a case in the visitor. See an example. Therefore, language-supported pattern matching is much more preferable than library support for the same.

Passing overloaded lambdas to std::visit---the fancy way to create a visitor. User-defined deduction guides for overloading from lambdas.

Algorithms implemented using pattern matching style tend to concentrate the entire algorithm in a function as opposed to object-oriented programming style where the algorithm is spread in multiple classes and potentially multiple files.

Sharing state become much easier with inheritance as opposed to std::variant based decomposition.

Too much ceremony in std::variant approach as you have to call std::visit and pass a visitor to it. In object-oriented style, it is just a call to a function and hence it’s very succinct.

Recursive std::variant is not possible without recursive_variant. std::variant is a container not an abstraction. std::variant alone isn’t sufficient to implement algebraic data types or the Composite design pattern.

std::variant disables fluent interfaces.

A summary of differences between inheritance and std::variant –based modeling alternatives in C++.

Deep Immutability in C++. C++ const is shallow. A raw pointer does not forward const-ness, propagate_const does. You can now implement deep Immutability in C++ using propagate_const.

A class containing propagate_const is not copy-assignable. This is consistent with basic C++ rule that a pointer to const can’t be assigned to pointer to non-const.

Mutable temporaries in C++. Yes, temporaries can be modified. Modern C++ provides ways to control this. See why you may need std::move(*this);.

The Named Parameter Idiom---an example of fluent interface in C++. 

Avoid constructing unnecessary temporary objects when fluent interfaces are used with immutable objects.

How to disambiguate between r-value reference qualified functions and l-value reference qualified functions. *this in a r-value qualified function is a l-value. The trick is to return a r-value reference to *this. Hence std::move(*this), which is a simply a cast.

Thank you!


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