C++11 - Initializer lists

In previous version of C++ standard (C++03) we was able to do following array elements assignment:
But we have not been able to do similar assignments to vector:
In order to assign above three elements to vector we had to invoke push_back() method three times:
C++11 present feature which help with above inconvenience. This feature can be achieved thanks to initializer_list template. In C++11, vector implementation has assignment operator taking initializer_list template as parameter:
Thanks to that we can use following assignments to vector:
The same way we can overload assignement operator of any of own class, as well as constructor or any function. Such definition can can take initializer_list template as parameter. Then we will be able to pass initialization list having syntax:

{ element1, element2, element3,...}

as parameter of such function.
Of course STL vector container has implemented constructor having initializer_list as parameter, too. So you can also initialize vector that way:
Having that knowledge and understanding two previously described new features of C++11:
- range-based for loop
- auto type
We can simplify following code written in C++03:
to following quick and simplified form in C++11:
Comfortable, more readable and time saving, right? I agree.

Comments

Blog's new layout

As you noticed this blog has new layout from today. I hope you like it. I think new layout looks better and more modern than previous one. Please, write you opinion about new layout in comments. If you have some ideas how to make this blog better, all ideas are welcomed. Enjoy new layout and blog articles.

STL - count and count_if algorithms

One of the basic and most useful STL algorithms is algorithm which can be used to count number of elements within selected container according to specified criteria. In order to do that we can use std::count or std::count_if algorithm. std::count (firstElementIterator, lastElementIterator, elementForSearch) - is function which will go through container using firstElementIterator and lastElementIterator and return number of container elements which value is equal elementForSearch std::count_if (firstElementIterator, lastElementIterator, UnaryPredicateFunction) - is function which examine range from firstElementIterator to lastElementIterator and return number of container elements which fulfill UnaryPredicateFunction criteria. UnaryPredicateFunction is function having following signature: bool functionName(const Type& a) . So, count_if returns number of elements where UnaryPredicateFunction returns true for. For better understanding let's take a...

QT - foreach algoriithm with const references performance improvement

Today I would like to show you optimal way of using foreach QT algorithm . I will show you why we should pass elements of foreach algorithm by const reference instead of passing them by value. Let me explain it on the below example: Output of this example is: In point I we are creating 3 objects of MyClass class and push them to myClasses QList element. In point II we are using QT foreach algorithm to invoke getValue() method for each object from myClasses list. As you can see on output text for that part of code we are invoking copy constructor before and destructor after invoking getValue() function. It is because we are passing each myClasses list element to foreach algorithm by value. Therefore we are copying that element at the beginning of foreach loop step and removing them (destructing) at the end. This is inefficient solution, especially when class of object being copied is big. It decreases performance. of our application. Solution for that i...

Developer Adventure

Search This Blog