By Fernando Pelliccioni | Oct 22, 2014 10:30 AM | Tags: None
Writing min function, part 4: Const-Correctness
by Fernando Pelliccioni
From the Article:
This is the fourth article of the series called “Writing min function”.
I still have to solve two mistakes made in the code of the previous posts. One of them is C++ specific, and the other it is a mistake that could be made in any programming language.
By Blog Staff | Oct 22, 2014 04:52 AM | Tags: None
Recently on Codexpert, an enthusiastic and very readable reaction to two fresh standards proposals that will be considered two weeks from now at the ISO C++ meeting in Urbana-Champaign, Illinois, USA:
Extension methods in C++
by Marius Bancila
From the article:
... if
x.f(y)andf(x,y)were equivalent it would be very easy to write the above code like this:auto v = std::vector<int> {1,2,3,4,5,6,7,8,9}; auto s = v.where([](int e){return e % 2 == 0; }) .select([](int e){return e*e; }) .sum();Isn’t that beautiful? I think it is.
...
The N4174 paper is rather an exploration of possibilities for uniform calling syntax than a very formal proposal. There are various aspects that have to be carefully considered especially when considering how to treat
f(x, y). The N4165 paper makes a good case of the uniform calling syntax, explains the benefits better and argues against treatingf(x)equivalent tox.f(). You should go ahead and read the two papers for detailed information. However, I sincerely hope that one day this will be accepted and become a core feature of the C++ language.
By Blog Staff | Oct 21, 2014 10:47 AM | Tags: basics
Quick A: No, but unordered_map<string, unique_ptr<MyClass>>::erase and unordered_map<string, shared_ptr<MyClass>>::erase do.
Today on SO:
std::unordered_map<std::String, myClass*>-- doesstd::unordered_map::erase()callmyClass' DTor?Assume I have some
unordered_mapof pointers to class instances, would erasing an object from that map also delete the instance?(rewording the question:) If I wanted to delete that instance, which version would be right?
if(it != map.end()) { delete it->second; map.erase(it); }or simply
if(it != map.end()) map.erase(it);?
By Blog Staff | Oct 21, 2014 10:34 AM | Tags: experimental advanced
If you're a very advanced C++ developer with an appetite for template mechanics, these two articles that were posted in the past 24 hours may interest you.
Note: The vast majority of C++ developers don't need to know this, but very advanced developers will find the material and the techniques interesting.
SFINAE and enable_if
by Eli Bendersky
Customization Point Design in C++11 and Beyond
by Eric Niebler
By Blog Staff | Oct 20, 2014 10:09 AM | Tags: None
Modern C++, modern apps:
How Microsoft is taking on the cross-platform challenge with Office
by Mary Jo Foley
Summary: Microsoft's Office team has a new approach designed to allow it to share more of Office's code across not just Windows, but also Android, iOS and the Web.
Note: This is a 50-minute version of the same talk given at CppCon in two one-hour sessions. After presenting this at CppCon, Igor was invited to present the information also at Facebook's @Scale.
See also Dropbox's CppCon talk about how Dropbox uses a similar architecture, and moved to C++ to enable a single cross-platform source base after initially having written separate apps in Java for Android and Objective-C for iOS.
From the article:
Zaika talked about Microsoft's Office cross-platform architecture strategy at the recent Facebook @Scale conference. ... In his 50-minute session, Zaika detailed how Microsoft is building Office across Windows, Apple, Android and the Web by using C++. ...
The goal is to maintain a shared core of intellectual property — the guts of Office — all written in C++ and keep that shared core as large as possible. By doing this, risks of document corruption are reduced. On top of that core, there is a set of native UX application programming interfaces. ...
The goal of "write once, run anywhere" which technologies like Java, Flash and HTML5 were designed to try to solve by pushing the level of abstraction as low as possible or making application programming interfaces (APIs) very broad sounded good, Zaika said, but ended up creating impedance mismatch. Compatibility and interoperability problems, among others, arose. "Either you blew up, or the OS (operating system) blew up," Zaika said. ...
With a common C++ core, a thin native UX layer and evolving PALs, Microsoft is building its Office apps so they work on different OSes with fairly little tweaking required. Zaika cited PowerPoint as an example, noting that only four percent of its tens of millions of lines are unique to the WinRT/Universal version of Office (the touch-first Office release some of us have been calling "Gemini"). If the XAML code is excluded, the amount of shared code is 98.6 percent he said. The PowerPoint for Android code base includes 95 percent shared code, Zaika said.
By Blog Staff | Oct 13, 2014 10:03 AM | Tags: None
Two regular expressions can go a long way.
Lightweight C++ options parser
by Jarryd Beck
From the article:
Using the new C++11 regular expressions, command line option parsing becomes trivial. I wrote a lightweight command line options parser because I was unsatisfied with all of the other libraries out there...
By Blog Staff | Oct 13, 2014 08:59 AM | Tags: None
Today on the Codexpert blog:
User-defined literals
by Marius Bancila
From the article:
The C++11 standard introduced the possibility to create user-defined literals, that are basically built-in type literals (
integer,float,charor string) followed by a used-defined suffix. User-defined literals enable the creation of new objects based on the built-in literal value and the applied user-defined suffix.auto temp = 77_fah; // 77 Fahrenheit degrees = 25 Celsius degrees auto size = 1_KB; // 1 kilobyte = 1024 bytes auto emp = "marius"_dev; // a user defined type Developer
By Blog Staff | Oct 13, 2014 05:41 AM | Tags: None
Fresh over the weekend, and in this morning's Standardization feed:
N4128: Ranges for the Standard Library
by Eric Niebler
From the article:
Eleven months ago, I began work on an updated range library for modern C++. Yesterday, I submitted a proposal to the C++ standardization committee to add ranges to the Standard Library. The proposal presents a vision for a future Standard Library that is familiar and yet more powerful, more usable, and more efficient than today’s.
My goal is nothing less than to change how C++ programmers write code. Seriously.
By Blog Staff | Oct 10, 2014 07:14 AM | Tags: None
Overload 123 is now available. It contains the following C++-related articles, and more:
[No pun intended. --Ed.] How do you return a default value given a condition? Malcolm Noyes presents solutions using older and newer C++ techniques.
Debugging any program can be time consuming. Sergey Ignatchenko and Dmytro Ivanchykhin extend their mathematical model to consider the effect of assertions.
The Visitor pattern can involve non-local boilerplate code. Robert Mill and Jonathan Coe present an inline VISITOR in C++.
By Blog Staff | Oct 9, 2014 08:41 AM | Tags: basics
Quick A: Because it performs worse than C++98 for common types like string and vector. The preferred way to optimize for rvalues is to add a && overload.
Fresh on SO:
Why is value taking setter member functions not recommended in Herb Sutter's CppCon 2014 talk (Back to Basics: Modern C++ Style)?
In Herb Sutter's CppCon 2014 talk Back to Basics: Modern C++ Style he refers on slide 28 (a web copy of the slides are here) to this pattern:
class employee { std::string name_; public: void set_name(std::string name) noexcept { name_ = std::move(name); } };He says that this is problematic because when calling
set_name()with a temporary, noexcept-ness isn't strong (he uses the phrase "noexcept-ish").Now, I have been using the above pattern pretty heavily in my own recent C++ code mainly because it saves me typing two copies of set_name() every time -- yes, I know that can be a bit inefficient by forcing a copy construction every time, but hey I am a lazy typer. However Herb's phrase "This noexcept is problematic" worries me as I don't get the problem here: std::string's move assignment operator is noexcept, as is its destructor, so set_name() above seems to me to be guaranteed noexcept. I do see a potential exception throw by the compiler before set_name() as it prepares the parameter, but I am struggling to see that as problematic.
Later on on slide 32 Herb clearly states the above is an anti-pattern. Can someone explain to me why lest I have been writing bad code by being lazy?
