Today many template libraries supply object generators to simplify object creation by utilizing the C++ template argument deduction facility. Consider
std::pair. In order to instantiate this class template and create a temporary object of this instantiation, one has to supply template parameters, as well as parameters to the constructor:
std::pair<int, double>(5, 3.14159);
To avoid this duplication, STL supplies the
std::make_pair object generator. When it is used, the types of template parameters are deduced from supplied function arguments:
For the temporary objects it is enough. However, when a named object needs to be allocated, the problem appears again:
std::pair<int, double> p(5, 3.14159);
The object generator no longer helps:
std::pair<int, double> p = std::make_pair(5, 3.14159);
It would be nice to deduce the type of the object (on the left) from the expression it is initialized with (on the right), but the current C++ syntax does not allow for this.
The above example demonstrates the essence of the problem but does not demonstrate its scale. Many libraries, especially expression template libraries, create objects of really complex types, and go a long way to hide this complexity behind object generators. Consider a nit Boost.Lambda functor:
_1 > 15 && _2 < 20
If one wanted to allocate a named copy of such an innocently looking functor, she would have to specify something like this:
lambda_functor< lambda_functor_base< logical_action<and_action>, tuple< lambda_functor< lambda_functor_base< relational_action<greater_action>, tuple< lambda_functor<placeholder<1> >, int const > > >, lambda_functor< lambda_functor_base< relational_action<less_action>, tuple< lambda_functor<placeholder<2> >, int const > > > > > > f = _1 > 15 && _2 < 20;
Not exactly elegant. To solve this problem (as well as some other problems), the C++ standard committee is considering a few additions to the standard language, such as
auto (see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1607.pdf).
typeof operator (or
decltype, which is a slightly different flavor of
typeof) allows one to determine the type of an expression at compile time. Using
typeof, the above example can be simplified drastically:
typeof(_1 > 15 && _2 < 20) f = _1 > 15 && _2 < 20;
Much better, but some duplication still exists. The
auto type solves the rest of the problem:
auto f = _1 > 15 && _2 < 20;
The purpose of the Boost.Typeof library is to provide a library-based solution, which could be used until the language-based facility is added to the Standard and becomes widely available.
Source code: https://github.com/boostorg/typeof
C and C++ are the most powerful programming language in the world. Most of the super fast and complex libraries and algorithms are written in C or C++. Most powerful Kernel programs are also written in C. So, there is no way to skip it.
In programming competitions, most programmers prefer to write code in C or C++. Tourist is considered the worlds top programming contestant of all ages who write code in C++.
During programming competitions, programmers prefer to use a lightweight editor to focus on coding and algorithm designing. Vim, Sublime Text, and Notepad++ are the most common editors for us. Apart from the competition, many software developers and professionals love to use Sublime Text just because of its flexibility.
I have discussed the steps we need to complete in this blog post before running a C/C++ code in Sublime Text. We will take the inputs from an input file and print outputs to an output file without using
freopen file related functions in C/C++.
#cpp #c #c-programming #sublimetext #c++ #c/c++
If you are familiar with C/C++then you must have come across some unusual things and if you haven’t, then you are about to. The below codes are checked twice before adding, so feel free to share this article with your friends. The following displays some of the issues:
The below code generates no error since a print function can take any number of inputs but creates a mismatch with the variables. The print function is used to display characters, strings, integers, float, octal, and hexadecimal values onto the output screen. The format specifier is used to display the value of a variable.
A signed integer is a 32-bit datum that encodes an integer in the range [-2147483648 to 2147483647]. An unsigned integer is a 32-bit datum that encodes a non-negative integer in the range [0 to 4294967295]. The signed integer is represented in twos-complement notation. In the below code the signed integer will be converted to the maximum unsigned integer then compared with the unsigned integer.
#problems-with-c #dicey-issues-in-c #c-programming #c++ #c #cplusplus
A new C# compiler feature that inspects code and generates additional source files promises to improve performance in a number of scenarios.
Microsoft has introduced a preview of a C# compiler capability called Source Generators that can inspect a program and generate source files that can be added to a compilation. Microsoft says Source Generators can improve performance in a number of scenarios.
Introduced April 29, a Source Generator is a piece of code (a .NET Standard 2.0 assembly) that runs during compilation and can inspect a program to produce additional files that are compiled together with the rest of the code.
#c #c# #c++ #programming-c
In this Video We are going to see how to use Loops in C++. We will see How to use For, While, and Do While Loops in C++.
C++ is general purpose, compiled, object-oriented programming language and its concepts served as the basis for several other languages such as Java, Python, Ruby, Perl etc.
#c #c# #c++ #programming-c
In this article, we’ll take a look at using the isdigit() function in C/C++. This is a very simple way to check if any value is a digit or not. Let’s look at how to use this function, using some simple examples.
#c programming #c++ #c #c#