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Core C++, 7 and 8 of N: Loops, ODR, and variadic array sorter

By Blog Staff | Feb 5, 2013 11:31 AM | Tags: intermediate advanced

Two advanced talks by Stephan T. Lavavej (aka STL) are now available, the second being posted today:

Core C++, 7 of N

In Part 7, STL teaches us about Usual Arithmetic Conversions, Template Metaprogramming (TMP), and shares some of the Visual C++ STL internal implementation (some of it not yet released). Many of you have asked for some treatment of TMP and STL delivers!

Core C++, 8 of N

In part 8, STL digs into the do-while loop, casts, one definition rule (ODR), and his variadic template array sorter. There is a lot of information in this episode, so get comfortable, tune in, and learn.

Boost 1.53.0 Released

By marshall | Feb 4, 2013 10:48 AM | Tags: None

Release 1.53.0 of the Boost C++ Libraries is now available.

These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use.

This release contains five new libraries and numerous enhancements and bug fixes for existing libraries.

New Libraries:

  • Atomic: C++11-style atomic<>, from Helge Bahmann, maintained by Tim Blechmann.
  • Coroutine: Coroutine library, from Oliver Kowalke.
  • Lockfree: Lockfree data structures, from Tim Blechmann.
  • Multiprecision: Extended precision arithmetic types for floating point, integer and rational arithmetic from John Maddock and Christopher Kormanyos.
  • Odeint: Solving ordinary differential equations, from Karsten Ahnert and Mario Mulansky.

Links:

Thanks,

--The Boost release team

   Beman Dawes
   Daniel James
   Eric Niebler
   Marshall Clow
   Rene Rivera
   Vladimir Prus

B-Tree Containers from Google

By Eric Niebler | Feb 1, 2013 11:06 AM | Tags: None

Google has graciously gifted to the community a set of STL-like containers that use B-trees under the covers. The code has been released under the Apache 2 license.

C++ Containers That Save Memory And Time

We’re pleased to announce C++ B-Tree, a C++ template library that implements B-tree containers with an analogous interface to the standard STL map, set, multimap, and multiset containers. B-trees are well-known data structures for organizing secondary storage, because they are optimized for reading and writing large blocks of data. But the same property that makes B-trees appropriate for use with databases and file systems also makes them appropriate for use in main-memory, just with smaller blocks. [...]

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Online C++ compilers

By Blog Staff | Jan 31, 2013 11:29 AM | Tags: None


Many people don't realize how many web pages offer access to try out C++ compilers, including many of the latest compilers with burgeoning C++11 language support. So we thought we'd publish a list.

Do you:

  • want to try out C++, but don't have a compiler installed?
  • want to try out a C++11 feature your compilers don't yet support?
  • want to compare the results of compiling a test program using different compilers?

Then try one of these online compilers! Some are compile-only to let check whether your code is legal, and some let you also run your test programs to see their output. For each, we include a list of the compilers that the page currently supports -- they include the latest from Clang (3.2, Dec 2012), GCC (4.8.0 prerelease), Intel (13.0, Oct 2012), and Microsoft (VC++ alpha CTP, Nov 2012).

This list is now also available on the Get Started! page.

Quick Q: What can I do with a moved-from object? -- StackOverflow

By Blog Staff | Jan 31, 2013 08:18 AM | Tags: basics

Quick A: It's a valid object with an unspecified state, so start by using member functions that have no preconditions. For example, assign a new value to the object.

What can I do with a moved-from object?

Does the standard define precisely what I can do with an object once it has been moved from? I used to think that all you can do with a moved-from object is do destruct it, but that would not be sufficient...

Effective C++11 update -- Scott Meyers

By Blog Staff | Jan 30, 2013 05:40 PM | Tags: intermediate basics

This week, Scott Meyers posted a couple of updates on how C++11 is coming to one of the world's most-loved C++ book series -- Effective C++.

 

First, here's Scott's preamble about his approach to Effective C++11:

Effective C++11: Background

I've mentioned in some earlier posts that I plan to start writing a new book, Effective C++11.  The purpose of this post is to tell you a little bit about it. Lest there be confusion, let me emphasize that there is no book yet. If everything falls into place the way I hope it will, there will be a book about 10 months from now. If. I'm not making any promises. [...]

 

As a followup, Scott then posted an early draft list of candidate Items for Effective C++11 as part of this post:

Effective C++11: Content and Status

[...] At last year's C++ and Beyond, I gave a talk entitled "Initial Thoughts on Effective C++11." It had my usual guideline format. I also gave a talk on "Secrets of the C++11 Threading API," which consisted of observations about C++11's threading support. The material in those talks, combined with the feedback I got from giving them and mixed in with my experience explaining the idea of universal references, ultimately yielded the initial list of candiate Items for EC++11. The current snapshot of my vision for Effective C++11 is: [...]

At least a million developers are looking forward to your book, Scott!

No pressure.

Quick Q: How to use std:: pointers to implement data structures (say, a DAG)? -- StackOverflow

By Blog Staff | Jan 30, 2013 07:13 AM | Tags: basics

This is a good specific example of a very common question about how to use smart pointers in data structures:

weak_ptr VS shared_ptr in graph node parent list

I have a directed acyclic graph implemented by Graph and Node classes. Each node has a list of pointers to children and a list of pointers to parents. [...] The Child list uses std::shared_ptr so that nodes are kept in memory at least as long as they have parents. But I don't want a node to own its parents, so I used weak_ptr for the pointers to parents.

But then there was a problem with the algorithms...

 

Quick Q: Can an enum class be converted to the underlying type? -- StackOverflow

By Blog Staff | Jan 29, 2013 01:59 PM | Tags: basics

Quick A: Yes, but it requires an explicit cast. One of the key differences between enum and enum class: the latter has no implicit conversion to the underlying type.

Can an enum class be converted to the underlying type?

Is there a way to convert an enum class field to the underlying type? I thought this would be automatic, but apparently not.

enum class my_fields : unsigned { field = 1 };

unsigned a = my_fields::field;

That assignment is being rejected by GCC. error: cannot convert 'my_fields' to 'unsigned int' in assignment.

Quick Q: Why do 'auto x = my_x;' and 'X& x = my_x;' declare different types? -- StackOverflow

By Blog Staff | Jan 29, 2013 08:49 AM | Tags: basics

Quick A: Remember that you can add things like const and & to an auto type...

'auto' and explicit variable declaration behaving differently

I have something like this:

[...]

auto bar1 = foo.GetBar();
auto bar2 = foo.GetBar(); //address of bar2 != address of bar1. why?

Bar& bar3 = foo.GetBar();
Bar& bar4 = foo.GetBar(); //address of bar3 == address of bar4.

What's going on here?

In a nutshell: To move or not to move -- Martin Moene

By matt | Jan 28, 2013 03:31 PM | Tags: basics

[Ed.: If you're new to C++11 and wondering about move semantics, but find the longer "introductory" articles about it a little too detailed, here's a nice nutshell discussion with a simple example and good links for further reading.]

An introductory discussion of the new C++11 rvalue references in connection with move semantics:

To Move or Not To Move

by Martin Moene

I'm probably not the only one who needs some time to become familiar with the new C++11 rvalue references. Recall std::auto_ptr to take care of a resource's lifetime. It could catch you by surprise and cause the loss of something valuable with its unconditional move behaviour.

 

Well that's exactly why things changed in C++11.

Here are a few excerpts that helped me to put the new rvalue references in perspective. ...

Continue reading...