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zero-overhead C++17 currying & partial application -- Vittorio Romeo

By Vittorio Romeo | Jan 30, 2017 04:42 AM | Tags: c++17

This article briefly explains the concepts of "currying" and "partial application", then covers the design and C++17 implementation of a generic zero-overheader constexpr `curry` function.

zero-overhead C++17 currying & partial application

by Vittorio Romeo

From the article:

[...] many features introduced in the latest C++ standards allow functional patterns to thrive in your codebase, [...] like currying and partial application. [...] In this article we're going to:

* Introduce and briefly explain the two aforementioned concepts.

* Write a generic constexpr zero-overhead `curry` function in C++17.

* Analyze the generated assembly of the implementation to prove the lack of overhead.

[...]

Given a generic function object `f`, invoking `curry(f)` will return a curried/partially-applicable version of `f`. If `f` is constexpr-friendly, the returned one will be as well. `curry` should not introduce any overhead compared to hand-written currying/partial application.

Istream Idiosyncrasies -- Adi Shavit

By Adi | Jan 30, 2017 04:41 AM | Tags: None

Idiosyncrasies with istreams.

Istream Idiosyncrasies

by Adi Shavit

From the article:

A lot has been written and the vice and virtues of the C++ iostreams library.
While working on Argh, my little C++11 argument parsing library, I ran across some somewhat surprising idiosyncrasies and a few interesting lessons.

The Future of Generic Programming -- How to design good concepts and use them well -- Stroustrup

By Blog Staff | Jan 23, 2017 04:08 PM | Tags: None

This new paper by Bjarne Stroustrup has been brewing over the holidays, and is now ready for release as a prepublication draft:

Concepts: The Future of Generic Programming
or, How to design good concepts and use them well

by Bjarne Stroustrup

From the draft paper:

Conclusions

Concepts complete C++ templates as originally envisioned. I don’t see them as an extension but as a completion.

Concepts are quite simple to use and define. They are surprisingly helpful in improving the quality of generic code, but their principles – and not just their language-technical details – need to be understood for effective use. In that, concepts are similar to other fundamental constructs, such as functions. Compared to unconstrained templates, there are no run-time overheads incurred by using concepts.

Concepts are carefully designed to fit into C++ and to follow C++’s design principles:

  • Provide good interfaces
  • Look for semantic coherence
  • Don’t force the user to do what a machine does better
  • Keep simple things simple
  • Zero-overhead

Don’t confuse familiarity and simplicity. Don’t confuse verbosity with “easy to understand.” Try concepts! They will dramatically improve your generic programming and make the current workarounds (e.g., traits classes) and low-level techniques (e.g., enable_if – based overloading) feel like error-prone and tedious assembly programming.

Const, Move and RVO--Bartlomiej Filipek

By Adrien Hamelin | Jan 23, 2017 02:21 PM | Tags: performance intermediate

const does not prevent (N)RVO, youhou.

Const, Move and RVO

by Bartlomiej Filipek

From the article:

C++ is a surprising language. Sometimes simple things are not that simple in practice. Last time I argued that in function bodies const should be used most of the time. But two cases were missed: when moving and when returning a value.

Does const influence move and RVO?

Pros and Cons of Alternative Function Syntax in C++--Petr Zemek

By Adrien Hamelin | Jan 18, 2017 03:01 PM | Tags: c++11 basics

Do you know the trailing return type?

Pros and Cons of Alternative Function Syntax in C++

by Petr Zemek

From the article:

C++11 introduced an alternative syntax for writing function declarations. Instead of putting the return type before the name of the function (e.g. int func()), the new syntax allows us to write it after the parameters (e.g. auto func() -> int). This leads to a couple of questions: Why was such an alternative syntax added? Is it meant to be a replacement for the original syntax? To help you with these questions, the present blog post tries to summarize the advantages and disadvantages of this newly added syntax...

Ranges: the STL to the Next Level--Jonathan Boccara

By Adrien Hamelin | Jan 16, 2017 12:55 PM | Tags: intermediate boost

Ranges are coming!

Ranges: the STL to the Next Level

by Jonathan Boccara

From the article:

The C++ Standard Template Library (STL) is a fantastic tool for making code more correct and expressive. It is mainly composed of two parts:

  • The containers, such as std::vector or std::map for instance,
  • The algorithms, a fairly large collection of generic functions that operate amongst others on containers. They are mostly found under the algorithm header.