Dimensional Data

In C++11 and C++14, we were able to use this math.h library in C++ applications. After the C++17 standard, this library modernized math operations with the cmath library. Functions are declared in  header. For compatibility reasons the is an optional alternative to support older code. In this post, we list most of these mathematical functions declared in the header of modern C++. What is cmath mathematical functions library in C++? The CMath Mathematical Special Functions Header  defines mathematical functions and symbols in the std namespace. It includes the previous math functions. It may also define them in the global namespace. You have to add a std namespace using namespace std; or you should use the std:: prefix for each math function. Some of the mathematical special functions are added to the C++17 cmath library header by the contents of the former international standard ISO/IEC 29124:2010 and math.h functions added too. These are only available in namespace std. If you do not use namespace you should add std:: prefix to use these modern math functions. In general, they are mostly double functions and can be slower, but they have more accurate results. For example sin() uses double variables, sinf() uses a float variable (same as C++11, faster, less accurate), while sinl() is used with long double variables (same as C++11, also slower, but more accurate). Here is a simple C++ example using the sin function.   #include #include   int main() { double d = std::sin(1.0); // double float  f = std::sinf(1.0); // float (C++11) long double  l = std::sinl(1.0); // long double (C++11)   }   What are the CMath mathematical special functions in modern C++ 17? There are many new modern mathematical special functions in the C++17 cmath header. Such as functions for associated Laguerre polynomials, elliptic integral of the first kind functions, Cylindrical Bessel functions (of the first kind), Cylindrical Neumann functions, Exponential integral functions, Hermite polynomials functions, Legendre polynomials functions, Laguerre polynomials, Riemann zeta function, and some spherical functions. Here is a list of the CMath special functions. Description double float long double Associated Laguerre polynomials assoc_laguerre assoc_laguerref assoc_laguerrel Associated Legendre polynomials assoc_legendre assoc_legendref assoc_legendrel Beta function beta betaf betal Elliptic integral of the first kind (complete) comp_ellint_1 comp_ellint_1f comp_ellint_1l Elliptic integral of the second kind (complete) comp_ellint_2 comp_ellint_2f comp_ellint_1l Elliptic integral of the third kind (complete) comp_ellint_3 comp_ellint_3f comp_ellint_1l Regular modified cylindrical Bessel functions cyl_bessel_i cyl_bessel_if cyl_bessel_il Cylindrical Bessel functions (of the first kind) cyl_bessel_j cyl_bessel_jf cyl_bessel_jl Irregular modified cylindrical Bessel functions cyl_bessel_k cyl_bessel_kf cyl_bessel_kl Cylindrical Neumann functions cyl_neumann cyl_neumannf cyl_neumannl Elliptic integral of the first kind (incomplete) ellint_1 ellint_1f ellint_1l Elliptic integral of the second kind (incomplete) ellint_2 ellint_2f ellint_2l Elliptic integral of the third kind (incomplete) ellint_3 ellint_3f ellint_3l Exponential integral expint expint expint Hermite polynomials hermite hermitef hermitel Legendre polynomials legendre legendref legendrel Laguerre polynomials laguerre laguerref laguerrel Riemann zeta function riemann_zeta riemann_zetaf riemann_zetal spherical associated Legendre functions sph_legendre sph_legendref sph_legendrel spherical Bessel functions (of the first kind) sph_bessel sph_besself sph_bessell spherical Neumann functions sph_neumann sph_neumannf sph_neumannl Note that, by the C++20 standard, only default names of math functions are used. For example, the laguerre() is used for the float, double and long double versions. For more details about changes in C++17 standard, please see this https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0226r1.pdf C++ Builder is the easiest and fastest C and C++ compiler […]

The features of C++17 were a big step in the history of C++ and brought a lot of new features. In C++17, there are new auto rules for direct-list-initialization. This feature in C++, changes the rules for auto deduction from a braced-init-list. In this post, we explain what these new rules for auto deduction with examples are. What is auto keyword in C++? The auto keyword arrives with the new features in C++11 and improved in C++17, can be used as a placeholder type specifier (an auto-typed variable), or it can be used in function declaration, or in a structured binding declaration. The auto keyword can be used with other new CLANG standards like C++14, C++17, etc. What are the new rules for auto deduction in C++ 17? In C++17, For copy-list-initialization, the auto deduction will either deduce a std::initializer_list (if the types of entries in the braced-init-list are all identical) or be ill-formed otherwise. Note that, auto a = {1, 2, 3}, b = {1}; remains unchanged and deduces initializer_list. This change is intended as a defect resolution against C++14. Now, let’s see the examples below. Auto deduction from braced-init-list Rule #1 For direct list-initialization: For a braced-init-list with only a single element, the auto deduction will deduce from that entry. In the example below, there is a single member in the braced-init-list, and this is automatically defined as an initializer_list that consists of int members.   auto a = { 30 }; // decltype(a) is std::initializer_list for (auto i : a)  std::cout

In modern programming sometimes we want to use a sequence of integers that are created at compile-time. In C++14, the std::integer_sequence is a class template for the sequence of integers that is generated at compile-time. In this post, we explain what integer sequence (std::integer_sequence) is in modern programming. What is the integer sequence (std::integer_sequence) in C++ 14? In C++14, the std::integer_sequence is a class template defined in a header that can be used for the sequence of integers generated at compile-time. In some cases, looping through a range of numbers whose span is unknown is used and, in these cases, we can use the std::integer_sequence integer sequence. Thus, we can create a sequence of integers at compile time. Our application knows the sequence of integers before it runs, and we use them on runtime as a package. In other words, the std::integer_sequence is used to hold a sequence of integers which can be turned into a parameter pack. We can use integer_sequence in template programming or meta-programming algorithms, and this will make our code faster and less complex. In C++14, a simple syntax for the std::integer_sequence can be written as shown below.   template class integer_sequence;   Here, T is the type of integers and val is a parameter pack of integers. Is there a simple integer sequence (std::integer_sequence) example in C++ 14? Here is a simple example how we can use std::integer_sequence.   template void print_sequence2(std::integer_sequence) { ( (std::cout

C++14 brought us a lot of useful things that we use today. One of the great features of C++14 was the member initializers and aggregates feature that a class with default member initializers may now be an aggregate. In this post, we explain how can use member initializers and aggregates with examples. What are the member initializers and aggregates features in C++14? With the new C++14, a class or struct with default member initializers may now be an aggregate in definition. “If there are fewer initializer-clauses in the list than there are members in the aggregate, then each member not explicitly initialized shall be initialized from its brace-or-equal-initializer or, if there is no brace-or-equal-initializer, from an empty initializer list“. Here is an example,   struct st_X { int a; int b = 100; }; st_X X = { 5 };   Here, X.b will be 100 automatically. Are there simple examples about member initializers and aggregates features in C++14? This feature can be good to be used with default values (i.e. “Unknown”), here is an example.   struct st_student { std::string name; int score; std::string uni = “Unknown”; };   st_student s0 = { “David Millington”}; st_student s1 = { “Yilmaz Yoru”, 98 }; st_student s2 = { “Ian Barker”, 99, “Harvard University” };   Here, David will have 0 score and “Unknown” university, Yilmaz will have “Unknown” university. We can use parameters in the next parameters.   struct st_test {  const char* str; int a; int val = str[a]; }; st_test test = { “ABCD”, 2 };   Here example above, value of test.val is initiated automatically to 67 which is third char ‘C’. Is there a full example about member initializers and aggregates feature in C++14? Here is a full example. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35   #include #include   struct st_student { std::string name; int score; std::string uni = “Unknown”; };   struct st_test {  const char* str; int a; int val = str[a]; };   struct st_X { int a; int b = 100; };   int main() { st_student s0 = { “David Millington”}; st_student s1 = { “Yilmaz Yoru”, 98 }; st_student s2 = { “Ian Barker”, 99, “Harvard University” };   std::cout