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By Adrien Hamelin | Apr 20, 2018 12:27 PM | Tags: intermediate c++17
What do you think?
optional<T> in Containers Ⅱ — Not All std::vector Usages Are The Same
by Jonathan Müller
From the article:
Okay, so in the previous post I talked about putting optional<T> in container. I came to conclusions which I though were reasonable at the time, however, people — rightfully — pointed out some flaws in my argumentation...
By Vittorio Romeo | Apr 18, 2018 12:18 PM | Tags: c++17
This article covers various compile-time "iteration" constructs that rely on the upcoming "familiar template syntax for lambdas" C++20 feature.
compile-time iteration with C++20 lambdas
by Vittorio Romeo
From the article:
In this article I'm going to show you how to implement the above constructs, relying on a new nifty addition to C++20 lambdas: [P0428: "Familiar template syntax for generic lambdas"], by Louis Dionne. [...]
It shows how to implement constructs for the following operations:
Iterating over a list of types;
Iterating over a list of compile-time values;
Iterating over a compile-time integral range;
Enumerating a list of types alongside their indices.
The code provided works on g++ 8
By Adrien Hamelin | Apr 17, 2018 12:36 PM | Tags: stl intermediate
Did you ever try?
How to Pass a Polymorphic Object to an STL Algorithm
by Jonathan Boccara
From the article:
As we can read in the opening chapter of Effective C++, C++ is a federation of 4 languages:
- the procedural part coming from C,
- the object-oriented part,
- the STL part (following a functional programming paradigm),
- the generic part with templates.
And what’s more, all of those 4 sub-languages are part of one whole: the C++ language. Those 4 paradigms begin united in one language gives opportunities for them to interact – and often, those interactions create interesting situations.
Today we’re focusing on one particular interaction, between the object-oriented model and the STL. There could be multiple forms for this interaction, and the case we will look at is how to pass a polymorphic (that is, having virtual methods) function object to an STL algorithm.
By Adrien Hamelin | Apr 17, 2018 12:18 PM | Tags: advanced
What is your opinion?
Contra built-in library types
by Arthur O’Dwyer
From the article:
C++ has several guiding principles or mantras. The most famous one is probably “zero-cost abstraction,” but for my money the most important one is “C++ does not have a string type.”
By Adrien Hamelin | Apr 17, 2018 12:17 PM | Tags: performance advanced
Optimise or not?
uninitialized_tag in C++
by Marius Elvert
From the article:
No doubt, C++ is one of those languages you can use to squeeze out every last drop of your CPU’s processing power. On the other hand, it also allows a high amount of abstraction. However, micro-optimization seldom works well with nice abstractions...
By Adrien Hamelin | Apr 16, 2018 01:00 PM | Tags: c++17 advanced
The power of C++17.
C++17: The two line visitor explained
by Marius Elvert
From the article:
If you have ever used an “idiomatic” C++ variant datatype like Boost.Variant or the new C++17 std::variant, you probably wished you could assemble a visitor to dispatch on the type by assembling a couple of lambda expressions like this:
auto my_visitor = visitor{ [&](int value) { /* ... */ }, [&](std::string const& value) { /* ... */ }, };
By Adrien Hamelin | Apr 16, 2018 12:51 PM | Tags: intermediate
More on the STL.
Moving Ranges Around with STL Algorithms
by Jonathan Boccara
From the article:
We’ve seen various ways to achieve complex operations on ranges with STL algorithms along the posts of the STL Learning Resource.
Let’s now see how to just move collections around. A much simpler topic…
…or is it?
By Adrien Hamelin | Apr 16, 2018 12:46 PM | Tags: advanced
Quick A: The behaviour will likely stay the same.
Recently on SO:
With “-fno-exceptions”, what happens with “new T”?
The way I understand it, operator new is defined by libstdc++. If you now compile your own code with -fno-exceptions, you cannot catch any exceptions, but you will still be linking against the normal version of libstdc++, which does throw an exception.
So yes, new T will throw an exception, even with -fno-exception.
However, if you compiled libstdc++ with -fno-exception as well, things become different. Now, new T cannot throw an exception but, if I read the libstdc++ manual right it will call abort() instead.
It seems that, if you want your new T to return NULL on failure, the only way is to explicitely specify nothrow...
By Adrien Hamelin | Apr 12, 2018 10:29 AM | Tags: intermediate
It's all about expressiveness.
Tailor Standard Containers to Your Needs
by Arne Mertz
From the article:
We often use standard containers as members of our classes. In a lot of cases, the semantics we actually need is not equivalent to the semantics the containers provide...
By Adrien Hamelin | Apr 12, 2018 10:24 AM | Tags: intermediate
Depends!
Which One Is Better: Map of Vectors, or Multimap?
by Jonathan Boccara
From the article:
While advising on how to make code more expressive on the SFME project, I came across an interesting case of choosing the right data structure, which I’ll share with you with the permission of the authors of the projects.
We had to associate a key with several values, and perform various operations. Should we use a map of vectors, or is a multimap more appropriate? Let’s see the case in more details, and compare the two solutions...