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Common Algorithm Patterns -- Scott Prager

By Jeremy Wright | Feb 19, 2015 07:44 AM | Tags: range intermediate efficiency algorithm

An interesting article concerning ranges, and how to make the ever useful algorithm header even more effective:

Common algorithm patterns

by Scott Prager

From the article:

Of the STL, <algorithm> may be the most well-used non-container library, but often requires a level of verbosity that requires just as much typing as the hand-written loop, making it not always feel so convenient. It benefits code that uses it with increased clarity and mathematical soundness, so reducing the syntactic overhead should be a goal of those using it. Today I will talk about these problems and demonstrate ways of making it more terse and sound.

C++17 Library Papers for Cologne - Part II

By Meeting C++ | Feb 19, 2015 02:30 AM | Tags: None

The second and last part in my miniseries about the library papers for next weeks LWG Meeting:

C++17 Library Papers for Cologne - Part II

by Jens WEller

From the article:

This is the second part about the papers for the Library Working Group Meeting in Cologne next week. The last part already covered some interesting papers, and gives an impression on what will be included into the Standard Library for C++17...

Convenient Constructs For Stepping Through a Range of Values -- Mikhail Semenov

By Blog Staff | Feb 17, 2015 11:33 AM | Tags: None

A timely article, as there has been an extensive flurry of discussion within the committee over the past weekend about defaults for the ranged for:

Convenient Constructs For Stepping Through a Range of Values

by Mikhail Semenov

From the article:

In this article, the following loops are proposed:

for (auto x : step(start, count, step-width)) { ... }

for (auto x : step(count)) {...}

for (auto x : step_backward(count)) {...}

for (auto x : step_to(start, finish, step-width)) {...}

for (auto x : step_until(start, finish, step-width)) {...}

They are based on the C++11 for-range loop. In order to write such loops, the appropriate functions step, step_backward, step_to and step_until have to be implemented.  The article shows their implementation, discusses advantages of such loops and includes the benchmark results.

Null Pointer Dereferencing Causes Undefined Behavior

By Andrey Karpov | Feb 16, 2015 05:42 AM | Tags: undefined behavior nullptr null pointer c++

I have unintentionally raised a large debate recently concerning the question if it is legal in C/C++ to use the &P->m_foo expression with P being a null pointer. The programmers' community divided into two camps. The first claimed with confidence that it wasn't legal while the others were as sure saying that it was. Both parties gave various arguments and links, and it occurred to me at some point that I had to make things clear.

Null Pointer Dereferencing Causes Undefined Behavior

by Andrey Karpov

From the article:

This code is incorrect in both C and C++ when the podhd pointer equals 0. If the pointer equals 0, undefined behavior occurs.

 

JSON Voorhees - Killer JSON for C++--Travis Gockel

By Adrien Hamelin | Feb 16, 2015 12:35 AM | Tags: intermediate c++11

Yet another JSON library for C++:

JSON Voorhees, GitHub link

by Travis Gockel

From the article:

JSON Voorhees is a JSON library written for the C++ programmer who wants to be productive in this modern world. What does that mean? There are a ton of JSON libraries floating around touting how they are "modern" C++ and so on. But who really cares? JSON Voorhees puts the focus more on the resulting C++ than any "modern" feature set. This means the library does not skip on string encoding details like having full support for UTF-8. Are there "modern" features? Sure, but this library is not meant to be a gallery of them – a good API should get out of your way and let you work. It is hosted on GitHub and sports an Apache License, so use it anywhere you need...

Iterators++, Part 2 -- Eric Niebler

By Felix Petriconi | Feb 15, 2015 01:17 PM | Tags: c++14 advanced

Eric Niebler goes deeper into Iterator details in his new blog post

 

Iterators++, Pat 2

by Eric Niebler

From the article:

This is the third in a series about proxy iterators, the limitations of the existing STL iterator concept hierarchy, and what could be done about it. In the first post I explained what proxy iterators are (an iterator like vector<bool>‘s that, when dereferenced, returns a proxy object rather than a real reference) and three specific difficulties they cause in today’s STL:

  1. What, if anything, can we say in general about the relationship between an iterator’s value type and its reference type?
  2. How do we constrain higher-order algorithms like for_each and find_if that take functions that operate on a sequence’s elements?
  3. How do we implement algorithms that must swap and move elements around, like sort and reverse?

C++17 Library Papers for Cologne

By Meeting C++ | Feb 14, 2015 03:36 AM | Tags: standardization intermediate committee c++17

The first part of a mini series about the Library Papers for the LWG Meeting in Cologne:

C++17 Library Papers for Cologne

by Jens Weller

From the article:

Last fall I did the last series about the Standardization papers for C++. I didn't had the time to finish the last part for the Library subgroup, as Meeting C++ 2014 was getting close too. I'll be attending the next meeting of the Library Working Group in Cologne, which is just a few days away, so I'll do a miniseries for the LWG papers...

Default Constructed Return Value: return {} -- Adi Shavit

By Adi | Feb 13, 2015 04:52 PM | Tags: c++11

Simplify your code using a default constructed return value with `return {}`:

Default Constructed Return Value: return {}

by Adi Shavit

From the article:

It is common for C/C++ functions to return default values, for example, if some internal condition fails.
This is straightforward for native return types. This pattern is often seen in factory methods or functions that return a polymorphic type via a base handle.

If the function has multiple early return points, this default construction needs to be repeated at each such point and each time stating the explicit return type just for calling the default ctor. This is annoying because the compiler already knows the return type.

Ranges and Iterators for numerical problems

By Meeting C++ | Feb 12, 2015 09:29 AM | Tags: performance intermediate c++11 boost

A guest blog post by Karsten Ahnert at Meeting C++ as a follow up of his talk!

Ranges and Iterators for numerical problems

by Karsten Ahnert

From the article:

In this blog post I am going to show some ideas how one can implement numerical algorithms with ranges. Examples are the classical Newton algorithm for finding the root of a function and ordinary differential equations. The main idea is to put the main loop of the algorithm into range such that the user can...